CN1497756A - Fuel cell and method of operation thereof - Google Patents

Abstract

A fuel cell is provided having a stack of unit cells, each unit cell including: a hydrogenion conductive electrolyte; an anode and a cathode with the hydrogen-ion conductive electrolyte interposed therebetween; an anode-side conductive separator in contact with the anode; and a cathode-side conductive separator in contact with the cathode, wherein the anode-side conductive separator has fuel gas passage grooves, facing the anode, for supplying a fu el gas to the anode, the cathode-side conductive separator has oxidant gas passage grooves, facing th e cathode, for supplying an oxidant gas to the cathode, and at least one of the fuel gas passage grooves and the oxidant gas passage grooves has an equivalent diameter of not smaller than 0.79 mm and not larger than 1.3 mm per each groove.

Description

Fuel cell and method of operation thereof

Background of the invention

A fuel cell simultaneously generates electricity and heat by electrochemically reacting a hydrogen-containing fuel gas with an oxygen-containing oxidant gas (such as air). Fuel cells are generally constructed by first forming a catalyst reaction layer on each surface of a polymer electrolyte film, which is mainly composed of electronically conductive carbon powder carrying a noble metal catalyst such as platinum. The thin film can selectively transfer hydrogen ions; then a gas diffusion layer is formed on the outer surface of the catalyst reaction layer, and the material of the diffusion layer is both gas permeable and electronically conductive, such as electronically conductive carbon paper and carbon fabric. The electrode includes a combination of catalyst reaction layer and gas diffusion layer.

Next, in order to prevent leakage of the supplied gas and avoid mixing of the two gases, a seal or gasket is arranged on the periphery of the electrodes, and the periphery of the polymer electrolyte membrane is blocked in a gap formed in the seal or gasket. The seal or gasket is pre-assembled as a single part with the electrodes and the polymer electrolyte membrane, forming a so-called "membrane-electrode assembly" (MEA). Electronically conductive separators are arranged outside the MEA to mechanically fix the MEA and electrically connect adjacent MEAs in series. The side of the separator in contact with the MEA is provided with gas flow channels for supplying fuel gas and oxidant gas to the electrodes and removing generated and excess gases. Although gas flow passages may be provided separately from the partitions, grooves are often formed on the surface of each partition to serve as gas flow passages.

In order to supply gas to these grooves, it is necessary to provide branch pipes for supplying gas according to the number of separators included in the fuel cell, and to directly connect the ends of the branch pipes to the grooves in the separators using pipe clamps. This fixture is called an external manifold. Another type of manifold is simpler in construction than the external manifold and it is called the internal manifold. The internal manifold is configured to form through holes in the partition having gas flow channels, each hole is connected to an inlet and an outlet of the gas flow channels, and gas is directly supplied to the gas flow channels from the through holes.

Since the fuel cell generates heat during operation, it is necessary to cool the fuel cell including the stacked unit cells in order to maintain it at an appropriate temperature. In general, a cooling member capable of supplying cooling water is provided between the separators of each to three unit cells; but it is often the case that cooling water used as a cooling member is provided on the rear surface of some separators. flow channel. The MEAs and partitions are alternately provided with cooling elements sandwiched between them, thereby assembling a stack of 10 to 200 MEAs. Typically, the stack is sandwiched between a pair of end plates by means of current collector plates and insulating plates, and secured by clamping bolts on both sides, thus forming a typical battery pack.

The battery pack is fixed with end plates, which can reduce the contact resistance between the electrolyte film, electrodes and separators, and can also ensure the gas tightness of the seals or gaskets; generally, a pressure higher than 10kg/cm ² should be applied. Therefore, it is generally customary to manufacture an end plate of metallic material excellent in mechanical strength, and then to fix this end plate by means of a clamping bolt incorporating a spring. Since humidified gas and cooling water come into contact with part of the end plate, stainless steel with better corrosion resistance than other metal materials is used for the end plate. On the other hand, for the current collector, a metal material having higher electron conductivity than carbon material is used. From the standpoint of contact resistance, there are some cases where a surface-treated metal material is used. Since the pair of end plates are electrically connected by clamping bolts, an insulating plate is inserted between the current collector plate and the end plates.

Separators used in such fuel cells are required to have high electronic conductivity, airtightness, and corrosion resistance (oxidation resistance). For this reason, the separator is made of a dense, electronically conductive carbon plate without gas permeability, and its surface is provided with gas channel grooves formed by cutting, or with a mixture of adhesive and electronically conductive carbon powder. Molding material obtained by molding and then baking.

In recent years, attempts have been made to replace carbon materials with metal plates such as stainless steel as separators. Separators made of sheet metal corrode when exposed to oxidizing atmospheres at high temperatures or when used for long periods of time. Corrosion of the metal plate increases the resistance and reduces the output efficiency. In addition, the dissolved metal ions diffuse into the polymer electrolyte and then become trapped in the exchange sites of the electrolyte, resulting in a decrease in the ionic conductivity of the polymer electrolyte itself. To avoid these degradations, the surface of the metal plate is thickly plated with a sufficient amount of gold.

Traditionally, materials composed of perfluorocarbon sulfonic acid are mainly used as polymer electrolytes. Since the polymer electrolyte can only exhibit ionic conductivity when it contains water itself, it is necessary to humidify the fuel gas and oxidant gas before supplying these gases to the MEA. In addition, since the reaction on the cathode side produces water, when these gases are humidified at a dew point temperature higher than the cell's operating temperature, water condensation occurs inside the cell and within the gas flow channels inside the electrodes. This causes phenomena such as water clogging, which creates problems of unstable or poor battery performance. This phenomenon is called an overflow phenomenon.

Also, when using a fuel cell as an automatic power generation system in our houses, the humidification of the fuel gas and oxidant gas needs to be systematic, and it is preferable to humidify at the lowest possible dew point in order to simplify the system and improve system efficiency. Therefore, it is common practice to humidify the gas at a dew point temperature slightly lower than the fuel cell temperature before supplying the gas to the fuel cell from the viewpoints of avoiding the flooding phenomenon, simplifying the system, improving system efficiency, and the like.

On the other hand, in order to enhance battery performance, it is required to improve the ionic conductivity of polymer electrolyte membranes. Thus, it is preferable to humidify the gas to a relative humidity close to 100% or not lower than 100%. In addition, from the viewpoint of durability of the polymer electrolyte membrane, it is preferable to supply the gas in a highly humid state. However, as described below, various problems arise when humidifying gases to near 100% relative humidity.

The first problem concerns the aforementioned flooding phenomenon. In order to avoid the overflow phenomenon, two measures can be considered: (1) prevent condensate water blockage in the gas channel groove; and prevent condensate water blockage inside the electrode. It is generally believed that the former measure is more effective. (2) Increase the gas pressure drop so that condensed water can be blown out. However, an increase in the gas pressure drop causes a drastic increase in auxiliary kinetic energy in the fuel cell system, such as that of the air supply blower and compressor, which reduces system efficiency.

The second problem is that the water wettability (contact angle) of the electrodes (the gas diffusion layer and the support carbon of the catalytic reaction layer) changes over time, resulting in the deterioration of the condensed water discharge over time, which has a negative impact on the durability of the battery. Influence.

The third problem is that the change over time in the water wettability of the electrodes causes the ratio of the flow rate of the gas flowing in the gas diffusion layer to the flow rate along the gas flow channels in the separator to change over time. Specifically, when the wettability within the gas diffusion layer increases with time, the amount of condensed water that can block the gas diffusion layer also increases with time, and the gas to be supplied to the electrodes stagnates in some parts. At the portion where the gas supply stagnates, the current density decreases. This makes the current density uneven across the electrode surface, resulting in poor battery performance and output power.

A fourth problem is that the water wettability of the electrodes changes over time, causing the amount of underflow gas between the flow channels in the separator to change over time. In the absence of a gas diffusion layer, the gas supplied into the gas flow channel naturally flows along the gas flow channel. But in fact, there is a gas diffusion layer adjacent to the gas flow channels, so that the underflow gas flows between the adjacent flow channels (for example, on the ribs between the gas channel grooves) through the gas diffusion layer.

For example, where the gas flow channel runs along a serpentine line extending from upstream to downstream and includes a plurality of horizontal pieces parallel to each other, gas flows in opposite directions in certain pairs of adjacent horizontal pieces. It can then be considered that the pressure drop of the gas flowing along the gas flow channel and the pressure drop of the underflow gas flowing through the gas diffusion layer from the upstream component to the downstream component balance.

When the wettability of the gas diffusion layer increases with time, the amount of condensed water in the gas diffusion layer also increases with time, but the underflow gas through the gas diffusion layer becomes stagnant. Of course, the smaller the pressure drop of gas flowing through the gas diffusion layer from the upstream component to the downstream component, the more likely this phenomenon will occur. In the case where the gas flow channel travels along a serpentine line, the amount of underflow gas flowing through the gas diffusion layer (especially near the curved portion of the gas flow channel) also decreases with time, whereby the gas supply tends to stagnate. At the portion of the gas diffusion layer where the gas supply is stagnant, the current density decreases, causing uneven current density on the surface of the battery, resulting in poor battery performance.

According to the above, the following two measures can be considered to avoid the overflow phenomenon: (1) avoid condensed water blocking in the gas channel groove; and (2) avoid condensed water blocking inside the electrode. It is considered more efficient not to allow condensate to overflow in the gas channel grooves. For this reason, it is basically effective to increase the pressure drop of the gas to be supplied to the gas flow passage groove; however, it is not practical to supply the gas with a pressure drop as high as over about 30 kPa.

It should be noted that, in order to improve the output power, efficiency, stability, etc. of the fuel cell, people have done a lot of research on the structural optimization of the gas channel groove (for example, Japanese Patent Publication No. 6-267564, Japanese Patent Publication No. Patent publication number flat 8-203546, Japanese published patent publication number 2000-231929, Japanese published patent publication number 2001-52723, Japanese published patent publication number 2001-76746).

Contents of the invention

The invention relates to a fuel cell including a hydrogen ion conductive electrolyte, which can be used for portable power sources, electric vehicle power sources, heat and power cogeneration systems, etc., and specifically relates to a fuel cell using a hydrogen ion conductive polymer electrolyte film.

Specifically, the present invention has been proposed in consideration of the above. The present invention relates to a fuel cell comprising a plurality of unit cells, each unit cell comprising: an anode and a cathode with a hydrogen ion conductive electrolyte interposed between the two electrodes ; an electronically conductive separator in contact with the anode on the anode side; and an electronically conductive separator in contact with the cathode on the cathode side, wherein the electronically conductive separator on the anode side includes fuel gas passage grooves facing the anode, For supplying fuel gas to the anode, the electron-conductive separator on the cathode side includes oxidant gas channel grooves, which face the cathode for supplying oxidant gas to the cathode, at least The equivalent diameter of one is: each groove is not less than 0.79mm and not more than 1.3mm.

Preferably, the depth of at least one of the fuel gas channel groove and the oxidant gas channel groove is not less than 0.7 mm and not greater than 1.1 mm.

Preferably, at least one of the fuel gas passage groove and the oxidizer gas passage groove runs along a serpentine line extending from upstream to downstream, and it includes a plurality of horizontal members parallel to each other and having substantially equal length "a" , wherein the ratio of the length "a" to the shortest linear dimension "b" of the horizontal piece at the most upstream side among the horizontal pieces and the horizontal piece at the lowermost side among the horizontal pieces satisfies the relationship: a/b≤1.2.

Preferably, at least one of the fuel gas passage groove and the oxidant gas passage groove runs along a serpentine line extending from upstream to downstream, and which comprises a plurality of levels parallel to each other and having substantially equal length "a" pieces, wherein the ratio of rib width "c" to length "a" between adjacent horizontal pieces satisfies the relationship: 1/200≤c/a≤1/20.

Preferably, the anode and the cathode each include a gas diffusion layer and a catalytic reaction layer in contact with the gas diffusion layer, and at least one of the gas diffusion layers at the anode and the cathode has a thickness of about 100 to 400 μm.

Preferably, at least one of the diffusion layers in the anode and cathode has a certain gas permeability along a direction parallel to its major surface, which is about 2×10 ⁻⁶ to 2× on a dry gas basis 10 ⁻⁸ m ² /(Pa·sec) (Pa·sec).

The invention also relates to a method of operating the aforementioned fuel cell.

It is preferable to operate the fuel cell under the condition that the pressure drop of at least one of the fuel gas flowing along the fuel gas channel groove and the oxidant gas flowing along the oxidant gas channel groove is not less than about 1.5 kPa (1 kPa =100mmAq (water column)), not more than about 25kPa.

It is preferable to operate the fuel cell under the condition that the ratio of the flow rate "f" of the underflow gas flowing into the anode to the flow rate "e" of the fuel gas flowing along the fuel gas channel groove satisfies the relationship: 0.05≦f/e≦0.43.

It is preferable to operate the fuel cell under the condition that the ratio of the flow rate "h" of the underflow gas flowing into the cathode to the flow rate "g" of the oxidant gas flowing along the oxidant gas channel groove satisfies the relationship: 0.05≦h/g≦0.43.

When the fuel cell further includes the cooling medium passage groove, it is preferable to operate the fuel cell under the following conditions: the inlet temperature of the cooling medium passage groove is about 45 to 75° C., and the fuel gas and the oxidant gas to be supplied to the fuel cell Among them, the dew point of at least one gas is not lower than -5°C and not higher than +5°C than the inlet temperature, and the utilization rate of the oxidant gas is not lower than about 30%, not higher than about 70%. The generating current density is not lower than 0.05A/cm ² and not higher than 0.3A/cm ² .

The underflow gas here refers to the gas flowing in the gas diffusion layer from upstream to downstream of the gas flow channel in a direction parallel to the main surface of the electrode.

According to the present invention, it is possible to solve or suppress the above-mentioned problem which occurs when fuel gas or oxidant gas humidified to a relative humidity close to 100% or not lower than 100% is supplied to a fuel cell without supplying a gas with a large pressure drop. question.

While the novel features of the present invention are set forth in the appended claims, the present invention will be better understood and understood in terms of organization and content from the following detailed description taken in conjunction with the accompanying drawings.

Description of drawings

The foregoing summary of the invention, as well as the following detailed description of preferred embodiments of the invention, are better understood when read in conjunction with the accompanying drawings. In order to clarify the invention, a presently preferred embodiment is shown in the drawings. It should be understood, however, that the invention is not limited to the precise construction and instrumentalities shown.

In the attached picture:

FIG. 1 is a cross-sectional view showing the structure of an MEA according to an example of the present invention.

Fig. 2 is a front view showing the structure of oxidant gas passage grooves in the separator used in Example 1 and each test example of the present invention.

FIG. 3 is a rear view showing the structure of fuel gas passage grooves in the separator of FIG. 2. FIG.

FIG. 4 is a rear view showing the structure of cooling water passage grooves in another partition plate of FIG. 2. FIG.

Fig. 5 is a front view showing the structure of oxidant gas passage grooves used in the separator of the fuel cell of Example 8 of the present invention.

FIG. 6 is a rear view showing the structure of fuel gas passage grooves in the separator of FIG. 5. FIG.

Detailed ways

In the case of condensed water and gas flowing along the gas channel groove, it is considered that the contact angle between the wall surface of the gas channel groove and water, the surface tension, and the equivalent diameter of the gas channel groove exert a great influence on the overflow of water. Influence. Especially when carbon is used as the material constituting the wall surface of the gas passage groove, the contact angle between carbon and water is limited, so the equivalent diameter of the gas passage groove exerts a great influence on the water overflow. It is to be noted that the equivalent diameter refers to the diameter of an equivalent circumference having the same area as the cross-sectional area of the groove space.

Using the groove depth and groove width, the equivalent diameter of the gas channel groove can be calculated by the following formula:

Equivalent diameter=2×(groove depth×groove width/π) ^1/2 .

In addition, when a certain taper is formed in the gas channel groove and/or a certain degree of chamfered curve appears in the edge portion, the equivalent diameter can be the cross section of the space surrounded by the plane including the rib top surface and the groove wall surface to determine the area.

In addition, when a certain taper is formed in the gas passage groove and/or there is a certain degree of chamfered curve at the edge portion, it should be within the straight line representing the shortest linear dimension between the plane including the top surface of the rib and the bottom surface of the groove. The midpoint determines the groove width.

The equivalent diameter of the groove is not less than 0.79mm, not more than 1.3mm, ideally not less than 1mm, not more than 1.2mm. When the equivalent diameter of the groove is less than 0.79 mm, an extremely large pressure drop is required to discharge condensed water; when it exceeds 1.3 mm, the gap between the electrode and the separator is wide, which increases the contact resistance.

In order to effectively prevent water overflow in the gas channel groove while maintaining battery performance, it is ideal that the depth of the groove is not less than 0.7 mm and not greater than 1.1 mm. When the groove depth is less than 0.7mm, a significant pressure drop is required to drain the condensate; when it exceeds 1.1mm, the separator needs to be thicker, making the volumetric efficiency of the battery pack impractical. On the other hand, the width of the gas passage groove is preferably shorter than 1.5 mm. Because when the width of the groove is not shorter than 1.5mm, the performance of the battery tends to deteriorate.

It should be noted that when the equivalent diameter of the gas channel groove is not less than 0.79mm, since the pressure drop is not less than 1.5kPa, almost all the water in the gas channel groove can be prevented from overflowing. However, even if the pressure drop is not less than 1.5kPa, when the equivalent diameter of each groove is less than 0.79mm, water overflow is likely to occur. In addition, even if the equivalent diameter is not less than 0.79mm, when the groove width is very long and the groove depth is as small as less than 0.7mm, water overflow may occur in individual cases.

In the fuel cell in a preferred mode of the present invention, at least one of the fuel gas passage groove formed in the anode-side electron-conductive separator and the oxidant gas passage groove formed in the cathode-side electron-conductive separator is Upstream travels toward a snaking line extending downstream. The groove comprises a plurality of horizontals parallel to each other and having substantially equal length "a".

Here, the time-dependent change in the water wettability of the electrodes leads to a time-dependent change in the state of the condensate flooding. In order to suppress this phenomenon, it is advisable to shorten the plurality of horizontal pieces of the gas passage groove, extend the shortest linear dimension "b" between the most upstream side horizontal piece and the most downstream side horizontal piece, and widen the horizontal pieces adjacent to each other. Ribs between horizontal pieces. However, in the case where the gas passage grooves advance along a serpentine line, when the horizontal piece is too short, the number of bends is increased in order to keep the flow passage at a certain length, thereby causing an increase in the gas pressure drop. In addition, when the ribs between horizontal members adjacent to each other are too wide, these ribs pressurize part of the gas diffusion layer, thereby preventing gas from being supplied into the pressurized member. It is therefore necessary to design the groove in such a way that the length of the horizontal piece and the number of bends are within the appropriate range.

It should be noted that in the case of overflow of condensed water, the larger the equivalent diameter of the flow channel, the more smoothly the water can be discharged. As the flow velocity of the gas underflow in the gas diffusion layer increases, the water discharge property also becomes poor. When the rib is widened, water discharge is improved by suppressing underflow gas.

Based on these viewpoints, in the first preferred mode of the present invention, the groove is designed such that the ratio of the length "a" to the shortest linear dimension "b" between the most upstream side horizontal member and the most downstream side horizontal member satisfies the relationship: a/b≤1.2. In addition, in the second preferred mode of the present invention, the groove should be designed such that the ratio of the rib width "c" to the length "a" between adjacent horizontal members satisfies the relationship: 1/200≤c/ a≤1/20. Here, when the ratio "a/b" exceeds 1.2, the horizontal member becomes too long to cause an increase in the pressure drop of the horizontal member between the elbows, thereby relatively increasing the amount of underflow gas. In addition, when the horizontal piece becomes too short, the number of bends increases too much, so it is preferable that the ratio best satisfy the relationship: 0.3≤a/b≤1.2. When the ratio "c/a" falls below 1/200, the number of bends increases, causing an increase in gas pressure drop; when the ratio "c/a" exceeds 1/20, the gas supplied to the gas diffusion layer becomes insufficient.

The water overflow inside the electrode and the change of wettability of the electrode with time are mostly controlled by the water overflow inside the gas diffusion layer. The gas diffusion layer preferably has high gas permeability and is as thin as possible. However, a thin gas diffusion layer (less than about 100 μm) that can impair the electron conductivity in the direction parallel to its main surface degrades the battery performance because the gas diffusion layer also has the current collecting effect of the electrode. In addition, when the thickness of the gas diffusion layer exceeds about 400 μm, its water discharge performance deteriorates while the amount of underflow gas in the diffusion layer increases sharply. It is therefore preferable to make the thickness of the gas diffusion layer approximately 100 to 400 µm. It is also preferable to have the thickness of the gas diffusion layer pressed by the ribs of the separator be 100 to 250 μm. Further, it is preferable that the gas permeability in the direction parallel to the main surface of the gas diffusion layer is about 2×10 ^-8 to 2×10 ^-6 m ² (Pa·sec) on a dry gas basis. When the gas permeability is below about 2×10 ^-8 m ² (Pa·sec), the gas supply to the catalytic layer of the electrode tends to be inhibited; when it exceeds about 2×10 ^-6 m ² (Pa·sec) When , the amount of underflow gas inside the gas diffusion layer increases too much.

As for the relationship between the flow velocity (f) of the subsurface gas flowing in the gas diffusion layer and the flow velocity (e) of the gas flowing along the gas passage grooves, it is preferable to let the flow velocity of the gas flowing along the gas passage grooves prevail. In order to maintain a proper relationship between these two flow rates, the ratio preferably satisfies the relationship: 0.05≤f/e≤0.43. When f/e is lower than 0.05, the gas supply to the catalyst to the electrode tends to be suppressed; when it exceeds 0.43, the amount of underflow gas inside the gas diffusion layer increases excessively.

Test example 1

Electronically conductive separators can be fabricated by cutting gas channel grooves on the surface of dense electronically conductive carbon plates that are not gas permeable. The equivalent groove diameter calculated from the groove width, groove depth, and groove cross-sectional area was used as a variable parameter for manufacturing various test separators. It is to be noted that the shape of the gas fluid passage is almost the same as that shown in FIG. 2 of Example 1, except that the groove width and the like are changed.

Considering the cutting process, since it is difficult to make the groove width shorter than 0.5mm, the groove width should not be shorter than 0.5mm. Furthermore, since it has been confirmed that fuel cell performance deteriorates when the groove width is longer than 1.5 mm, the groove width is varied in the range of 0.5 to 1.5 mm.

The groove depth is not more than 1.2 mm, because it has been confirmed that when the groove depth is longer than 1.2 mm, the separator becomes thicker, which is not practical, and also causes deterioration of fuel cell performance.

Then, a sealing gasket is arranged on the periphery of each test partition, and a transparent polyacrylonitrile fiber board is arranged on the surface of the partition, so that the state of the gas flowing along the gas channel groove can be observed. Add water droplets evenly into the gas channel grooves in the bulkhead. Then inject nitrogen or air into the gas channel groove, and its pressure drop is 1kPa (100mmAq), 1.5kPa (150mmAq), 2kPa (200mmAq), 5kPa (500mmAq) or 10kPa (1000mmAq). Then, determine by visual observation whether water droplets are likely to drain rapidly from the gas channel groove. The results are shown in Tables 1 to 7.

Table 1 Equivalent diameter (mm) 0.56 0.67 0.80 0.87 0.98 Width/Depth(mm) Width 0.5 Depth 0.5 Width 0.7 Depth 0.5 width 1.0 Depth 0.5 Width 1.2 Depth 0.5 Width 1.5 Depth 0.5 100mmAq x x x x x 150mmAq x x x x x 200mmAq x x x x x 500mmAq x x x △ ○ 1000mmAq x x △ ○ ○

×: water droplet overflow

Δ: Water droplets take time to discharge.

◯: Water droplets are quickly discharged.

Table 2 Equivalent diameter (mm) 0.62 0.73 0.87 0.96 1.07 Width/Depth(mm) Width 0.5 Depth 0.6 Width 0.7 Depth 0.6 width 1.0 Depth 0.6 Width 1.2 Depth 0.6 Width 1.5 Depth 0.6 100mmAq x x x x x 150mmAq x x x x △ 200mmAq x x x △ △ 500mmAq x x △ ○ ○ 1000mmAq △ △ ○ ○ ○

×: water droplet overflow

Δ: Water droplets take time to discharge.

◯: Water droplets are quickly discharged.

table 3 Equivalent diameter (mm) 0.67 0.79 0.94 1.03 1.16 Width/Depth(mm) Width 0.5 Depth 0.7 Width 0.7 Depth 0.7 width 1.0 Depth 0.7 Width 1.2 Depth 0.7 Width 1.5 Depth 0.7 100mmAq x x x x x 150mmAq x ○ ○ ○ ○ 200mmAq △ ○ ○ ○ ○ 500mmAq △ ○ ○ ○ ○ 1000mmAq ○ ○ ○ ○ ○

×: water droplet overflow

Δ: Water droplets take time to discharge.

◯: Water droplets are quickly discharged.

Table 4 Equivalent diameter (mm) 0.71 0.84 1.01 1.11 1.24 Width/Depth(mm) Width 0.5 Depth 0.8 Width 0.7 Depth 0.8 width 1.0 Depth 0.8 Width 1.2 Depth 0.8 Width 1.5 Depth 0.8 100mmAq x x x x x 150mmAq x ○ ○ ○ ○ 200mmAq △ ○ ○ ○ ○ 500mmAq △ ○ ○ ○ ○ 1000mmAq ○ ○ ○ ○ ○

×: water droplet overflow

Δ: Water droplets take time to discharge.

◯: Water droplets are quickly discharged.

table 5 Equivalent diameter (mm) 0.80 0.94 1.13 1.24 1.38 Width/Depth(mm) Width 0.5 depth 1.0 Width 0.7 depth 1.0 width 1.0 depth 1.0 Width 1.2 depth 1.0 Width 1.5 depth 1.0 100mmAq x x x x △ 150mmAq ○ ○ ○ ○ ○ 200mmAq ○ ○ ○ ○ ○ 500mmAq ○ ○ ○ ○ ○ 1000mmAq ○ ○ ○ ○ ○

×: water droplet overflow

Δ: Water droplets take time to discharge.

◯: Water droplets are quickly discharged.

Table 6 Equivalent diameter (mm) 0.83 0.99 1.18 1.30 1.45 Width/Depth(mm) Width 0.5 depth 1.1 Width 0.7 depth 1.1 width 1.0 depth 1.1 Width 1.2 depth 1.1 Width 1.5 depth 1.1 100mmAq x x x x △ 150mmAq ○ ○ ○ ○ ○ 200mmAq ○ ○ ○ ○ ○ 500mmAq △ ○ ○ ○ ○ 1000mmAq ○ ○ ○ ○ ○

×: water droplet overflow

Δ: Water droplets take time to discharge.

◯: Water droplets are quickly discharged.

Table 7 Equivalent diameter (mm) 0.87 1.03 1.24 1.35 1.51 Width/Depth(mm) Width 0.5 depth 1.2 Width 0.7 depth 1.2 width 1.0 depth 1.2 Width 1.2 depth 1.2 Width 1.5 depth 1.2 100mmAq x x x △ △ 150mmAq ○ ○ ○ ○ ○ 200mmAq ○ ○ ○ ○ ○ 500mmAq △ ○ ○ ○ ○ 1000mmAq ○ ○ ○ ○ ○

×: water droplet overflow

Δ: Water droplets take time to discharge.

◯: Water droplets are quickly discharged.

Test example 2

A separator was prepared which was the same as the separator having the smallest equivalent diameter of 0.79 mm (see Table 3, groove width: 0.7 mm, groove depth: 0.7 mm) among the test separators exhibiting good results in Test Example 1.

A separator was also prepared which had the largest equivalent diameter of 1.3 mm (see Table 6, groove width: 1.2 mm, groove depth: 1.1 mm) among the test separators exhibiting good results in Test Example 1. The board is the same. It should be noted that the separator selected here has a maximum equivalent diameter with a groove width of 1.2 mm because it is believed that a groove width exceeding 1.2 mm cannot obtain sufficient battery performance.

In addition, a separator was prepared which exhibited good results as in Test Example 1 and had a medium equivalent diameter of 1.13 mm between the aforementioned minimum and maximum equivalent diameters (see Table 5, groove width: 1 mm, groove depth : 1mm) is the same as the separator.

At the same time, electron-conductive carbon paper (manufactured by Toray Industries, Inc.) and carbon fabric constituting the gas diffusion layer were prepared. Even though electronically conductive carbon paper or carbon fabric can be used in the process of manufacturing fuel cells, when the thickness of the gas diffusion layer does not exceed 90 μm, it becomes difficult to handle the gas diffusion layer. In addition, the electron conductivity of the gas diffusion layer in a direction parallel to its surface is also insufficient, which causes deterioration in battery performance, so it was determined that the thickness of the gas diffusion layer is preferably not less than 100 μm.

Next, a sealing gasket is arranged on the periphery of each test partition, and a gas diffusion layer is arranged on the surface of the partition on the side of the gas channel groove. In addition, a transparent acrylic fiber sheet is provided on the gas diffusion layer so that the state in which nitrogen or air to which oil mist is added flows along the grooves of the gas passage can be observed. Next, the acrylic fiber sheet was clamped to the separator by applying a pressure of 7 kg/cm ² to the contact portion between the gas diffusion layer and the separator. The gas permeability of the gas diffusion layer varies according to the clamping pressure, and the higher the clamping pressure, the lower the gas permeability becomes. In this test example, a carbon fabric having a gas permeability of 1.2×10 ^-7 m ² /(Pa·sec) was used when the clamping pressure was 7 kg/cm ² .

Nitrogen or air was injected into the gas passage grooves of the resulting separator on which the gas diffusion layer was disposed. The gas pressure drop is then measured. At the same time, in the absence of a gas diffusion layer, a transparent acrylic fiber plate was arranged on the surface of the separator with a gasket on the periphery in the same manner as in Test Example 1, and the gas was injected into the gas channel groove. , to measure the gas pressure drop. Here, the gas is injected at the same rate as in the case of the separator on which the gas diffusion layer is provided. The ratio of the amount of underflow gas flowing in the gas diffusion layer to the amount of gas flowing along the gas channel grooves of the separator can be determined by the pressure drop both with and without the gas diffusion layer. In addition, the underflow state of the gas can also be observed. The results are shown in Tables 8 to 10.

Table 8 GDL thickness (μm) 100 200 300 400 450 Gas flow ratio (f/e) 0.10 0.18 0.31 0.50 0.76 gas underflow state ○ ○ ○ x x

GDL: gas diffusion layer

×: The gas in the GDL is in the state of rapid underflow when it flows from the gas inlet to the outlet.

○: The gas is in a uniform flow state along the flow channel.

Table 9 GDL thickness (μm) 100 200 300 400 450 Gas flow ratio (f/e) 0.07 0.15 0.29 0.46 0.70 gas underflow state ○ ○ ○ x x

GDL: gas diffusion layer

×: The gas in the GDL is in the state of rapid underflow when it flows from the gas inlet to the outlet.

○: The gas is in a uniform flow state along the flow channel.

Table 10 GDL thickness (μm) 100 200 300 400 450 Gas flow ratio (f/e) 0.05 0.11 0.25 0.43 0.66 gas underflow state ○ ○ ○ ○ x

GDL: gas diffusion layer

×: The gas in the GDL is in the state of rapid underflow when it flows from the gas inlet to the outlet.

○: The gas is in a uniform flow state along the flow channel.

As can be found from the results of tests carried out separately using fuel cells, when there is gas underflow (hereinafter referred to as fast underflow) on the ribs between the gas channel grooves, the gas flow state changes drastically with time, thus affecting the initial battery performance and The durability of battery performance is negatively affected.

Test example 3

A separator was prepared which was the same as that used in Experimental Examples 1 and 2 including gas passage grooves having an equivalent diameter of 1.13 mm (groove width: 1 mm, groove depth: 1 mm). In addition, various carbon fabrics having a thickness of not less than 200 μm are used as the gas diffusion layer. Except for using these carbon fabrics, the ratio of the amount of underflow gas flowing in the gas diffusion layer to the amount of gas flowing along the gas channel groove of the separator was determined in the same manner as in Test Example 2, and the obtained ratio, the underflow of gas The relationship between state and gas permeability of carbon fabrics is listed in Table 11.

Table 11 Gas permeability of GDL (m ³ /m ² /sec/Pa·m) 3×10 ^-6 2× ^10-6 2×10 ^-7 2× ^10-8 1×10 ^-8 Gas flow ratio (f/e) 0.52 0.43 0.2 0.05 0.03 gas underflow state x ○ ○ ○ △

GDL: gas diffusion layer

×: The gas in the GDL is in the state of rapid underflow when it flows from the gas inlet to the outlet.

Δ: The gas is slightly in a submerged state in the GDL.

○: The gas is in a uniform flow state along the flow channel.

It can be observed from the results of experiments carried out separately with fuel cells that when there is a fast underflow of gas from the inlet to the outlet of the gas channel groove in the gas diffusion layer, the state of the gas flow changes sharply with time, thus it affects the initial battery performance. And the durability of battery performance has a negative effect. It was also found that even when there is little gas underflow in the gas diffusion layer, the cell performance deteriorates.

example 1

(i) Manufacture of electrodes

Catalyst powder was prepared by allowing acetylene black powder (Denka-Black (product name), manufactured by Denki Kagaku Kogyo Kabushihikaisha) to support platinum particles having an average particle diameter of about 30 Å. In terms of weight, 25 parts by weight of platinum are used per 100 parts by weight of acetylene black powder. Suspension A was prepared by mixing the obtained catalyst powder with isopropanol. Further, perfluorocarbon sulfonic acid (Flemion (product name), manufactured by Asahi Glass Company) was mixed with ethanol to prepare a suspension B. Suspensions A and B are then mixed with each other to obtain a catalyst paste.

At the same time, a carbon fabric is prepared to constitute the gas diffusion layer. The carbon fabric used had an outer dimension of 12×12 cm, a thickness of 200 μm, and a gas permeability of 1.2×10 ⁻⁷ m ² /(Pa·sec). A mixture of carbon black powder and polytetrafluoroethylene (PTFE) (D-1 (product name), manufactured by DSIKININDUSTRIES LTD.) aqueous dispersion was applied to the surface of the carbon fabric on the side where the catalytic reaction layer was to be formed , and then baked at 400° C. for 30 minutes, so as to set a waterproof layer on the carbon fabric. The aforementioned catalyst paste was applied to the waterproof layer by screen printing to form a catalytic reaction layer. In this way, an electrode including a carbon fabric, a catalytic reaction layer formed on the carbon fabric, and a waterproof layer provided therebetween is obtained. The platinum content and the perfluorocarbon sulfonic acid content per unit area in the electrode were 0.3 mg/cm ² and 1.0 mg/cm ² , respectively.

(ii) Preparation of MEA

Description will be made with reference to FIG. 1 .

Each electrode in each pair of electrodes 14 including the catalytic reaction layer 12 and the gas diffusion layer 13 was adhered to each surface of a hydrogen ion conductive polymer electrolyte membrane 11 having an outer dimension of 20 cm×20 cm by hot pressing, said The bonding method is to make the catalytic reaction layer 12 contact with the electrolyte membrane 11 . For the hydrogen ion conductive polymer electrolyte membrane 11, perfluorocarbon sulfonic acid having been formed into a membrane with a thickness of 30 µm was used. Next, manifold holes having the same size and arrangement as those formed in a separator described later are formed on the periphery of the electrolyte membrane 11 . A gas seal 15 manufactured by Viton Co. was provided on the periphery of the electrolyte membrane so that electrodes and manifold holes were surrounded by the gas seal, whereby a membrane-electrode assembly (MEA) 16 was fabricated.

(iii) Manufacture of electronically conductive separators

The surface of a dense, electronically conductive carbon plate without gas permeability is cut to form grooves for gas passages, thereby fabricating electronically conductive separators. Three kinds of spacers are manufactured here: spacer (X), has formed groove shown in Figure 2 on its one surface, has formed the groove shown in Figure 3 on the other surface; Spacer (Y), Formed on one of its surfaces with grooves shown in Figure 2 and on the other surface with grooves shown in Figure 4; separator (Z) with grooves shown in Figure 3 formed on one surface , the groove shown in Figure 4 is formed on the other surface (the arrangement of the manifold holes is different). The grooves shown in Figures 2, 3 and 4 are oxidant gas passage grooves, fuel gas passage grooves and cooling water passage grooves, respectively.

The size of each partition is 20cm×20cm, and the thickness is 3mm. Each of the grooves 21a and 21b formed in each partition is a rectangular concave surface with a width of 0.7mm and a depth of .07mm, and the equivalent diameter of each groove is 0.79mm. The gas channel grooves run along a serpentine line extending from upstream to downstream, and they include a plurality of horizontal pieces, which are parallel to each other and have substantially the same length “a”, the length “a” being the horizontal piece on the most upstream side and The ratio a/b of the shortest linear dimension "b" between the horizontal members on the most downstream side was 1.2. In addition, the width "c" of the ribs 22a and 22b between the horizontal members adjacent to each other was 1.2 mm, and the ratio c/a of the rib width "c" to the length "a" was 1/30.

Next, prescribed manifold holes, namely, oxidant gas inlet 23a, oxidizer gas outlet 23b, fuel gas inlet 24a, fuel gas outlet 24b, and cooling water inlet 25a and cooling water outlet 25b, are provided on each separator. It should be noted that in each bulkhead, each manifold hole of the same size is provided in the same position. In addition, clamping rod holes 26 are also provided at the four corners of each partition.

(iv) Manufacture of fuel cells

The MEA was sandwiched between two previously specified separators, and they were used as unit cells. One surface of one MEA faces the oxidant gas passage groove in the separator (X), while the other surface faces the fuel gas passage groove in the separator (Z). The other MEA is arranged to face the fuel gas passage groove of the separator (X) of the unit cell while having its opposite side face the oxidant gas passage groove in the separator (Y). This two-cell construction pattern was repeated until a stack containing 100 cells was assembled. At each end of the battery pack, a gold-plated copper current collector plate, an insulating plate made of PPS (polyphenylene sulfide), and an end plate made of stainless steel are sequentially placed, and the end plate is fixed with a clamping rod. The clamping pressure against the electrodes was 10 kg/cm ² .

(v) Evaluation of fuel cells

The thus produced polymer electrolyte fuel cell of this example was kept at 70°C, and hydrogen gas humidified and heated to have a dew point of 70°C and air humidified and heated to have a dew point of 70°C were supplied to the anode side, respectively and cathode side. This produces an open-circuit battery voltage of 98V at no load when no current is being sourced externally.

The fuel cell was allowed to generate electricity continuously under the conditions of fuel utilization rate of 75%, oxygen utilization rate of 50%, and current density of 0.3 A/cm ² to measure output power performance over time. As a result, it was confirmed that the output power of the fuel cell of this example was maintained at 3.11 kW (72V-43.2A) after 8000 hours.

Example 2

The same fuel cell as in Example 1 was fabricated except that the groove structure in the separator was changed. The partition plate used here comprises grooves 21a and 21b, and in the structure of these grooves, except that the groove width is 1mm, the depth is 1mm and the equivalent diameter of each groove is 1.13mm, others are all the same as in example 1. have the same structure.

The ratio a/b of the length "a" of the horizontal member to the shortest linear dimension "b" between the most upstream horizontal member and the most downstream horizontal member and the ratio c/a of the rib width "c" to the length "a" are respectively Same as in Example 1.

The thus produced polymer electrolyte fuel cell of this example was kept at 70°C, and hydrogen gas humidified and heated to have a dew point of 70°C and air humidified and heated to have a dew point of 70°C were supplied to the anode side, respectively and cathode side. This produces an open-circuit battery voltage of 97.5V at no load when no current is being sourced externally.

The fuel cell was allowed to generate electricity continuously under the conditions of fuel utilization rate of 75%, oxygen utilization rate of 50%, and current density of 0.3 A/cm ² to measure output power performance over time. As a result, it was confirmed that the output of the fuel cell of this example was maintained at 3.132 kW (72.5V-43.2A) after 8000 hours.

Example 3

The same fuel cell as in Example 1 was fabricated except that the groove structure in the separator was changed. The spacer used here includes grooves 21a and 21b, and in the structure of these grooves, except that the groove width is 1.2 mm, the depth is 1.1 mm, and the equivalent diameter of each groove is 1.3 mm, others are the same as those of the example. 1 with the same structure.

The ratio a/b of the length "a" of the horizontal member to the shortest linear dimension "b" between the most upstream horizontal member and the most downstream horizontal member and the ratio c/a of the rib width "c" to the length "a" are respectively Same as in Example 1.

The thus produced polymer electrolyte fuel cell of this example was kept at 70°C, and hydrogen gas humidified and heated to have a dew point of 70°C and air humidified and heated to have a dew point of 70°C were supplied to the anode side, respectively and cathode side. This produces an open-circuit battery voltage of 98.5V at no load when no current is being sourced externally.

The fuel cell was allowed to generate electricity continuously under the conditions of fuel utilization rate of 75%, oxygen utilization rate of 50%, and current density of 0.3 A/cm ² to measure output power performance over time. As a result, it was confirmed that the output of the fuel cell of this example was maintained at 3.123 kW (72.3V-43.2A) after 8000 hours.

Example 4

The same fuel cell as in Example 1 was fabricated except that the groove structure in the separator was changed. The separator used here includes the grooves 21a and 21b, except that the groove width is 1 mm, the depth is 1 mm, the equivalent diameter of each groove is 1.13 mm, and the horizontal members adjacent to each other are separated in the structure of these grooves. The width "c" of each of the ribs 22a and 22b is 1 mm, and the ratio c/a of the rib width "c" to the length "a" of the horizontal member is 1/60, and the others are the same as in Example 1.

The ratio a/b of the horizontal member length "a" to the shortest linear dimension "b" between the most upstream side horizontal member and the most downstream side horizontal member is the same as in Example 1.

The thus manufactured polymer electrolyte fuel cell of this example was kept at 70°C, and hydrogen gas humidified and heated to have a dew point of 70°C and air humidified and heated to have a dew point of 70°C were supplied to the anode side, respectively and cathode side. This produces an open-circuit battery voltage of 98.5V at no load when no current is being sourced externally.

The fuel cell was allowed to generate electricity continuously under the conditions of fuel utilization rate of 75%, oxygen utilization rate of 50%, and current density of 0.3 A/cm ² to measure output power performance over time. As a result, it was confirmed that the output of the fuel cell of this example was maintained at 3.132 kW (72.5V-43.2A) after 8000 hours.

Example 5

The same fuel cell as in Example 1 was fabricated except that the groove structure in the separator was changed. The separator used here includes grooves 21a and 21b, and in the structure of these grooves, except that the groove width is 1 mm, the depth is 1 mm, the equivalent diameter of each groove is 1.13 mm, and the horizontal members adjacent to each other The width "c" of each rib 22a and 22b is 0.8mm, and the ratio c/a of the rib width "c" to the length "a" of the horizontal member is 1/200, the rest are the same as the structure in Example 1 .

The ratio a/b of the horizontal member length "a" to the shortest linear dimension "b" between the most upstream side horizontal member and the most downstream side horizontal member is the same as in Example 1.

The thus manufactured polymer electrolyte fuel cell of this example was kept at 70°C, and hydrogen gas humidified and heated to have a dew point of 70°C and air humidified and heated to have a dew point of 70°C were supplied to the anode side, respectively and cathode side. This produces an open-circuit battery voltage of 98.5V at no load when no current is being sourced externally.

The fuel cell was allowed to generate electricity continuously under the conditions of fuel utilization rate of 75%, oxygen utilization rate of 50%, and current density of 0.3 A/cm ² to measure output power performance over time. As a result, it was confirmed that the output of the fuel cell of this example was maintained at 3.123 kW (72.3V-43.2A) after 8000 hours.

Example 6

The same fuel cell as in Example 1 was fabricated except that the groove structure in the separator was changed. The separator used here includes grooves 21a and 21b, and in the structure of these grooves, except that the groove width is 1 mm, the depth is 1 mm, the equivalent diameter of each groove is 1.13 mm, and the length "a" of the horizontal member is equal to The ratio a/b of the shortest linear dimension "b" between the most upstream side horizontal piece and the most downstream side horizontal piece is 0.8, the width "c" of each rib 22a and 22b between the horizontal pieces adjacent to each other is 1mm, The structure was the same as in Example 1 except that the ratio c/a of the rib width "c" to the length "a" was 1/50.

The thus manufactured polymer electrolyte fuel cell of this example was kept at 70°C, and hydrogen gas humidified and heated to have a dew point of 70°C and air humidified and heated to have a dew point of 70°C were supplied to the anode side, respectively and cathode side. This produces an open-circuit battery voltage of 99V at no load when no current is being sourced externally.

The fuel cell was allowed to generate electricity continuously under the conditions of fuel utilization rate of 75%, oxygen utilization rate of 50%, and current density of 0.3 A/cm ² to measure output power performance over time. As a result, it was confirmed that the output of the fuel cell of this example was maintained at 3.154 kW (73V-43.2A) after 8000 hours.

Example 7

The same fuel cell as in Example 1 was fabricated except that the groove structure in the separator was changed. The separator used here includes grooves 21a and 21b, and in the structure of these grooves, except that the groove width is 1 mm, the depth is 1 mm, the equivalent diameter of each groove is 1.13 mm, and the length "a" of the horizontal member is equal to The ratio a/b of the shortest linear dimension "b" between the most upstream side horizontal piece and the most downstream side horizontal piece is 0.6, the width "c" of each rib 22a and 22b between the horizontal pieces adjacent to each other is 1mm, The structure was the same as in Example 1 except that the ratio c/a of the rib width "c" to the length "a" was 1/40.

The thus manufactured polymer electrolyte fuel cell of this example was kept at 70°C, and hydrogen gas humidified and heated to have a dew point of 70°C and air humidified and heated to have a dew point of 70°C were supplied to the anode side, respectively and cathode side. This produces an open-circuit battery voltage of 98.5V at no load when no current is being sourced externally.

The fuel cell was allowed to generate electricity continuously under the conditions of fuel utilization rate of 75%, oxygen utilization rate of 50%, and current density of 0.3 A/cm ² to measure output power performance over time. As a result, it was confirmed that the output of the fuel cell of this example was maintained at 3.11 kW (72V-43.2A) after 8000 hours.

Comparative example 1

The same fuel cell as in Example 1 was fabricated except that the groove structure in the separator was changed. The separator used here includes grooves 21a and 21b, and in the structure of these grooves, except that the groove width is 0.6 mm, the depth is 0.6 mm, the equivalent diameter of each groove is 0.68 mm, and the length of the horizontal member "a The ratio a/b to the shortest linear dimension "b" between the most upstream side horizontal piece and the most downstream side horizontal piece is 1.3, and the width "c" of each rib 22a and 22b between the horizontal pieces adjacent to each other is The structure is the same as in Example 1 except that the ratio c/a of the rib width "c" to the length "a" is 1/220.

The thus manufactured polymer electrolyte fuel cell of this example was kept at 70°C, and hydrogen gas humidified and heated to have a dew point of 70°C and air humidified and heated to have a dew point of 70°C were supplied to the anode side, respectively and cathode side. This produces an open-circuit battery voltage of 96V at no load when no current is being sourced externally.

The fuel cell was allowed to generate electricity continuously under the conditions of fuel utilization rate of 75%, oxygen utilization rate of 50%, and current density of 0.3 A/cm ² to measure output power performance over time. As determined from the results of operation of the example fuel cell over 2000 hours, its output decreased from 3.07kW (71V-43.2A) at the beginning to 2.85kW (66V-43.2A) after 2000 hours.

Comparative example 2

The same fuel cell as in Example 1 was fabricated except that the groove structure in the separator was changed. The separator used here includes grooves 21a and 21b, and in the structure of these grooves, except that the groove width is 1.2mm, the depth is 1.2mm, the equivalent diameter of each groove is 1.35mm, and the length of the horizontal piece "a The ratio a/b to the shortest linear dimension "b" between the most upstream side horizontal piece and the most downstream side horizontal piece is 1.3, and the width "c" of each rib 22a and 22b between the horizontal pieces adjacent to each other is 1.5 mm, and the ratio c/a of the rib width "c" to the length "a" is 1/19, other structures are the same as those in Example 1.

The thus manufactured polymer electrolyte fuel cell of this example was kept at 70°C, and hydrogen gas humidified and heated to have a dew point of 70°C and air humidified and heated to have a dew point of 70°C were supplied to the anode side, respectively and cathode side. This produces an open-circuit battery voltage of 96V at no load when no current is being sourced externally.

The fuel cell was allowed to generate electricity continuously under the conditions of fuel utilization rate of 75%, oxygen utilization rate of 50%, and current density of 0.3 A/cm ² to measure output power performance over time. It was determined from over 2000 hours of operation of the example fuel cell that its output dropped from 3.02kW (70V-43.2A) at the beginning to 2.76kW (64V-43.2A) after 2000 hours.

Example 8

The same fuel cell as in Example 1 was fabricated except that the groove structure in the separator was changed. As in Example 1, a dense electron-conductive carbon plate without gas permeability was cut to form gas passage grooves, thereby producing an electron-conductive spacer. Three types of spacers were manufactured here: spacer (O) with grooves shown in Figure 5 formed on one surface and grooves shown in Figure 6 on the other surface; spacer (P ), on one surface is formed the groove shown in Figure 5, on the other surface is formed the groove shown in Figure 4; separator (Q), on one surface is formed the groove shown in Figure 6 Grooves, the grooves shown in Fig. 4 are formed on the other surface (the arrangement of the manifold holes is different). The grooves shown in Figs. 5 and 6 are oxidant gas passage grooves and fuel gas passage grooves, respectively, and as in Example 1, the grooves shown in Fig. 4 are cooling water passage grooves.

As in Example 1, each separator had a size of 20 cm x 20 cm and a thickness of 3 mm. Each of the grooves 31a and 31b formed in each separator with a rectangular concave surface in cross section has a width of 0.7mm and a depth of 0.7mm, and the equivalent diameter of each groove is 0.79mm. The gas channel grooves run along a serpentine line extending from upstream to downstream, and they include a plurality of horizontal pieces parallel to each other and having substantially the same length "a", the length "a" being the most upstream side horizontal piece The ratio a/b to the shortest linear dimension "b" between the most downstream side horizontal member is 0.2. In addition, the width "c" of the ribs 32a and 32b between adjacent horizontal members is 0.7 mm, and the ratio c/a of the rib width "c" to the length "a" is 1/30. Note also that matrix-shaped flow passages 37 are provided between the most upstream horizontal piece and the manifold hole and between the most downstream horizontal piece and the manifold hole.

Next, prescribed manifold holes, ie, oxidant gas inlet 33a, oxidizer gas outlet 33b, fuel gas inlet 34a, fuel gas outlet 34b, and cooling water inlet 35a and cooling water outlet 35b, are provided on each separator. It should be noted that each manifold hole of the same size is provided in the same position in each bulkhead. In addition, clamping rod holes 36 are also provided at the four corners of each partition.

The thus manufactured polymer electrolyte fuel cell of this example was kept at 70°C, and hydrogen gas humidified and heated to have a dew point of 70°C and air humidified and heated to have a dew point of 70°C were supplied to the anode side, respectively and cathode side. This produces an open-circuit battery voltage of 98.5V at no load when no current is being sourced externally.

The fuel cell was allowed to generate electricity continuously under the conditions of fuel utilization rate of 75%, oxygen utilization rate of 50%, and current density of 0.3 A/cm ² to measure output power performance over time. As a result, it was confirmed that the output of the fuel cell of this example was maintained at 3.11 kW (72V-43.2A) after 8000 hours.

Example 9

The same fuel cell as in Example 8 was fabricated except that the groove structure in the separator was changed. The spacer used here includes grooves 31a and 31b, and in the structure of these grooves, except that the groove width is 1mm, the depth is 1mm, the equivalent diameter of each groove is 1.13mm, and each rib 32a and 32b The structure was the same as in Example 8 except that the width "c" was 1 mm and the ratio c/a of the rib width "c" to the length "a" was 1/20.

The ratio a/b of the horizontal member length "a" to the shortest linear dimension "b" between the most upstream side horizontal member and the most downstream side horizontal member is the same as in Example 8.

The thus manufactured polymer electrolyte fuel cell of this example was kept at 70°C, and hydrogen gas humidified and heated to have a dew point of 70°C and air humidified and heated to have a dew point of 70°C were supplied to the anode side, respectively and cathode side. This produces an open-circuit battery voltage of 98V at no load when no current is being sourced externally.

The fuel cell was allowed to generate electricity continuously under the conditions of fuel utilization rate of 75%, oxygen utilization rate of 50%, and current density of 0.3 A/cm ² to measure output power performance over time. As a result, it was confirmed that the output of the fuel cell of this example was maintained at 3.119 kW (72.2V-43.2A) after 8000 hours.

Example 10

The same fuel cell as in Example 8 was fabricated except that the groove structure in the separator was changed. The separator used here includes grooves 31a and 31b, and in the structure of these grooves, except that the groove width is 1.2mm, the depth is 1.1mm, the equivalent diameter of each groove is 1.3mm, each rib 32a and The structure of 32b is the same as that in Example 8 except that the width "c" of 32b is 1 mm and the ratio c/a of the rib width "c" to the length "a" is 1/20.

The ratio a/b of the length "a" of the horizontal member to the shortest linear dimension "b" between the horizontal member on the most upstream side and the horizontal member on the most downstream side is the same as in Example 8.

The thus manufactured polymer electrolyte fuel cell of this example was kept at 70°C, and hydrogen gas humidified and heated to have a dew point of 70°C and air humidified and heated to have a dew point of 70°C were supplied to the anode side, respectively and cathode side. This produces an open-circuit battery voltage of 98.5V at no load when no current is being sourced externally.

The fuel cell was allowed to generate electricity continuously under the conditions of fuel utilization rate of 75%, oxygen utilization rate of 50%, and current density of 0.3 A/cm ² to measure output power performance over time. As a result, it was confirmed that the output of the fuel cell of this example was maintained at 3.136 kW (72.6V-43.2A) after 8000 hours.

Example 11

The same fuel cell as in Example 1 was fabricated except that the groove structure in the separator was changed. The separator used here comprises grooves 21a and 21b. In the structure of these grooves, except that the width of the groove is 1mm, the depth is 0.79mm, and the equivalent diameter of each groove is 1mm, others are all the same as those in Example 1. in the same structure.

The ratio a/b of the length "a" of the horizontal member to the shortest linear dimension "b" between the most upstream horizontal member and the most downstream horizontal member is 1, and the ratio c/a of the rib width "c" to the length "a" is 1/50.

The thus manufactured polymer electrolyte fuel cell of this example was kept at 70°C, and hydrogen gas humidified and heated to have a dew point of 70°C and air humidified and heated to have a dew point of 70°C were supplied to the anode side, respectively and cathode side. This produces an open-circuit battery voltage of 98.5V at no load when no current is being sourced externally.

The fuel cell was allowed to generate electricity continuously under the conditions of fuel utilization rate of 75%, oxygen utilization rate of 50%, and current density of 0.3 A/cm ² to measure output power performance over time. As a result, it was confirmed that the output of the fuel cell of this example was maintained at 3.162 kW (73.2V-43.2A) after 8000 hours.

Example 12

The same fuel cell as in Example 1 was fabricated except that the groove structure in the separator was changed. The spacer used here includes grooves 21a and 21b. In the structure of these grooves, except that the width of the grooves is 1mm, the depth is 0.88mm, and the equivalent diameter of each groove is 1.06mm, the others are the same as those of the example. 1 with the same structure.

The ratio a/b of the length "a" of the horizontal member to the shortest linear dimension "b" between the most upstream horizontal member and the most downstream horizontal member is 1, and the ratio c/a of the rib width "c" to the length "a" is 1/50.

The thus manufactured polymer electrolyte fuel cell of this example was kept at 70°C, and hydrogen gas humidified and heated to have a dew point of 70°C and air humidified and heated to have a dew point of 70°C were supplied to the anode side, respectively and cathode side. This produces an open-circuit battery voltage of 99.5V at no load when no current is being sourced externally.

The fuel cell was allowed to generate electricity continuously under the conditions of fuel utilization rate of 75%, oxygen utilization rate of 50%, and current density of 0.3 A/cm ² to measure output power performance over time. As a result, it was confirmed that the output of the fuel cell of this example was maintained at 3.184 kW (73.7V-43.2A) after 8000 hours.

Example 13

The same fuel cell as in Example 1 was fabricated except that the groove structure in the separator was changed. The separator used here includes grooves 21a and 21b. In the structure of these grooves, except that the width of the grooves is 1.1mm, the depth is 1.03mm, and the equivalent diameter of each groove is 1.2mm, the others are the same as The structure in Example 1 is the same.

The ratio a/b of the length "a" of the horizontal member to the shortest linear dimension "b" between the most upstream horizontal member and the most downstream horizontal member is 1, and the ratio c/a of the rib width "c" to the length "a" is 1/50.

The thus manufactured polymer electrolyte fuel cell of this example was kept at 70°C, and hydrogen gas humidified and heated to have a dew point of 70°C and air humidified and heated to have a dew point of 70°C were supplied to the anode side, respectively and cathode side. This produces an open-circuit battery voltage of 99V at no load when no current is being sourced externally.

The fuel cell was allowed to generate electricity continuously under the conditions of fuel utilization rate of 75%, oxygen utilization rate of 50%, and current density of 0.3 A/cm ² to measure output power performance over time. As a result, it was confirmed that the output of the fuel cell of this example was maintained at 3.171 kW (73.4V-43.2A) after 8000 hours.

Example 14

The same fuel cell as in Example 1 was fabricated except that the groove structure in the separator was changed. The spacer used here includes grooves 21a and 21b, and in the structure of these grooves, except that the groove width is 1 mm, the depth is 0.75 mm, and the equivalent diameter of each groove is 0.98 mm, the others are the same as those of the example. 1 with the same structure.

The ratio a/b of the length "a" of the horizontal member to the shortest linear dimension "b" between the most upstream horizontal member and the most downstream horizontal member is 1, and the ratio c/a of the rib width "c" to the length "a" is 1/50.

The thus manufactured polymer electrolyte fuel cell of this example was kept at 70°C, and hydrogen gas humidified and heated to have a dew point of 70°C and air humidified and heated to have a dew point of 70°C were supplied to the anode side, respectively and cathode side. This produces an open-circuit battery voltage of 98V at no load when no current is being sourced externally.

The fuel cell was allowed to generate electricity continuously under the conditions of fuel utilization rate of 75%, oxygen utilization rate of 50%, and current density of 0.3 A/cm ² to measure output power performance over time. As a result, it was confirmed that the output of the fuel cell of this example was maintained at 3.119 kW (72.2V-43.2A) after 8000 hours.

Example 15

The same fuel cell as in Example 1 was fabricated except that the groove structure in the separator was changed. The spacer used here includes grooves 21a and 21b. In the structure of these grooves, except that the width of the grooves is 1.1mm, the depth is 1.06mm, and the equivalent diameter of each groove is 1.22mm, others are the same as The structure in Example 1 is the same.

The ratio a/b of the length "a" of the horizontal member to the shortest linear dimension "b" between the most upstream horizontal member and the most downstream horizontal member is 1, and the ratio c/a of the rib width "c" to the length "a" is 1/50.

The thus manufactured polymer electrolyte fuel cell of this example was kept at 70°C, and hydrogen gas humidified and heated to have a dew point of 70°C and air humidified and heated to have a dew point of 70°C were supplied to the anode side, respectively and cathode side. This produces an open-circuit battery voltage of 98.5V at no load when no current is being sourced externally.

The fuel cell was allowed to generate electricity continuously under the conditions of fuel utilization rate of 75%, oxygen utilization rate of 50%, and current density of 0.3 A/cm ² to measure output power performance over time. As a result, it was confirmed that the output of the fuel cell of this example was maintained at 3.128 kW (72.4V-43.2A) after 8000 hours.

Example 16

The same fuel cell as in Example 1 was fabricated except that the groove structure in the separator was changed. The spacer used here includes grooves 21a and 21b. In the structure of these grooves, except that the width of the grooves is 0.7mm, the depth is 0.81mm, and the equivalent diameter of each groove is 0.85mm, others are the same as The structure in Example 1 is the same.

The ratio a/b of the length "a" of the horizontal member to the shortest linear dimension "b" between the most upstream horizontal member and the most downstream horizontal member is 1, and the ratio c/a of the rib width "c" to the length "a" is 1/50.

The thus manufactured polymer electrolyte fuel cell of this example was kept at 70°C, and hydrogen gas humidified and heated to have a dew point of 70°C and air humidified and heated to have a dew point of 70°C were supplied to the anode side, respectively and cathode side. This produces an open-circuit battery voltage of 98V at no load when no current is being sourced externally.

The fuel cell was allowed to generate electricity continuously under the conditions of fuel utilization rate of 75%, oxygen utilization rate of 50%, and current density of 0.3 A/cm ² to measure output power performance over time. As a result, it was confirmed that the output of the fuel cell of this example was maintained at 3.123 kW (72.3V-43.2A) after 8000 hours.

Test example 4

As shown in Fig. 1, it can be seen from the visual observation of whether water droplets can be quickly discharged from the flow channel of the separator carried out in Test Example 1, when the depth of the groove is 0.5 mm, the width of the groove is 0.5 mm, 0.7 mm and 1mm and the gas pressure drop ranges from 1kPa (100mmAq) to 10kPa (1000mmAq), water droplets cannot be discharged quickly.

Here, the same operation as in Test Example 1 was performed except that the aforementioned separator was used and a gas having a pressure drop exceeding 10 kPa was injected into the gas channel groove, and it was determined by visual observation whether water droplets could be rapidly discharged from the channel groove of the separator . The results are shown in Table 12.

Table 12 Equivalent diameter (mm) 0.56 0.67 0.80 Width/Depth(mm) Width 0.5 Depth 0.5 Width 0.7 Depth 0.5 width 1.0 Depth 0.5 1500mmAq x x ○ 2000mmAq x △ ○ 2500mmAq △ ○ ○ 2700mmAq ○ ○ ○ 3000mmAq ○ ○ ○

×: water droplet overflow

Δ: Water droplets take time to discharge.

◯: Water droplets are quickly discharged.

From the above results, it was confirmed that, when a pressure drop of not less than 25 kPa was applied, water droplets could be rapidly discharged from the separator flow channel regardless of the equivalent diameter, width and depth of the gas flow channel groove. This therefore shows that when the pressure drop is in the range of not less than 1.5 kPa (150 mmAq) and not more than 25 kPa (2500 mmAq), effective effects can be brought to the present invention.

Example 17

A fuel cell similar to that in Example 1 was fabricated with the cooling water inlet temperature maintained at 40 to 80°C. A mixed gas containing 23% carbon dioxide, 76.5% hydrogen, 0.5% air, and 20ppm carbon monoxide that has been humidified and heated to have a dew point temperature equal to the cooling water inlet temperature is supplied to the anode side . Air that has been humidified and heated to have a dew point temperature equal to the cooling water inlet temperature is supplied to the cathode side.

The fuel cell was allowed to generate electricity continuously under the conditions of fuel utilization rate of 75%, oxygen utilization rate of 50%, and current density of 0.3 A/cm ² to measure output power performance over time. In addition, under the condition of a current density of 0.3A/cm ² , the cooling water flow rate was controlled during the continuous power generation process so that the temperature of the cooling water outlet was 6°C higher than that of the cooling water inlet.

Table 13 shows: the open circuit voltage of the battery under no load when no current is output to the outside; the standard deviation (σ) of the voltage change of 100 unit cells 100 hours after the start of continuous power generation; and 10000 hours after the start of continuous power generation The average rate of voltage drop (degradation rate) per hour.

Table 13 Cooling water inlet temperature (℃) Battery open circuit voltage (V) Voltage standard deviation (σ) Average speed of voltage drop (μv/h) 40 94 3.8 8.1 45 96 2.3 3.3 50 97 2.1 2.8 55 98 1.9 2.0 60 98 1.8 1.7 65 98 1.7 1.8 70 98 1.7 2.1 75 98 1.6 3.5 80 98 1.6 Impossible to work after 8000 hours

It can be seen from Table 13 that although the open circuit voltage of the battery is not greatly affected by the inlet temperature of the cooling water (battery temperature), when the inlet temperature of the cooling water is not higher than 40 °C, the electrode catalyst will be affected by the carbon monoxide in the fuel gas And poisoning, thus increasing the degradation rate and the initial eigenvalue σ. It was also seen that when the temperature of the cooling water inlet was not lower than 80°C, the voltage of the battery was lowered after about 8000 hours to make it impossible to continue the battery operation. Therefore, it can be considered that the temperature of the cooling water inlet is suitably 45 to 75°C, more preferably 50 to 70°C.

Example 18

A fuel cell similar to the one in Example 1 was fabricated with the cooling water inlet temperature maintained at 65°C. A mixed gas containing 23% carbon dioxide, 76.5% hydrogen, and 0.5% air is supplied to the anode side after being humidified and heated to a dew point temperature of -10°C to +10°C relative to the cooling water inlet temperature and 20ppm carbon monoxide. Air that has been humidified and heated to a dew point temperature of -10°C to +10°C relative to the cooling water inlet temperature is supplied to the cathode side.

The fuel cell was allowed to generate electricity continuously under the conditions of fuel utilization rate of 75%, oxygen utilization rate of 50%, and current density of 0.3 A/cm ² to measure output power performance over time. In addition, under the condition of current density of 0.3A/cm ² , the flow rate of cooling water was controlled during continuous power generation so that the temperature of the cooling water outlet was 6°C higher than the temperature of the cooling water inlet.

Table 14 shows: the open circuit voltage of the battery under no load when the current is not output to the outside; the standard deviation (σ) of the voltage change of 100 unit cells for 100 hours after the start of continuous power generation; and after the start of continuous power generation The average rate of voltage drop (degradation rate) per hour for 10,000 hours.

Table 14 Dew point of supply gas relative to cooling water inlet temperature (°C) Battery open circuit voltage (V) Voltage standard deviation (σ) Average speed of voltage drop (μv/h) -10 93 2.1 Impossible to work after 7000 hours -5 96 1.8 4.3 0 98 1.7 1.8 +5 98 2.3 2.0 +10 98 4.5 6.5

It can be seen from Table 14 that although the open circuit voltage of the battery is not greatly affected by the dew point of the supply gas, it is affected by the blockage of condensed water in the gas flow channel when the dew point of the supply gas is 10 °C higher than the cooling water inlet temperature, The initial eigenvalue σ increases. It was also seen that when the dew point of the supply gas was 10°C lower than the temperature of the cooling water inlet, the battery voltage dropped to such an extent that the battery could not continue to operate after 7000 hours. From the above, it can then be considered that the suitable dew point range of the supply gas is -5°C to +5°C relative to the temperature of the cooling water inlet.

Example 19

A fuel cell similar to the one in Example 1 was fabricated with the cooling water inlet temperature maintained at 65°C. A mixed gas containing 23% carbon dioxide, 76.5% hydrogen, 0.5% air, and 20 ppm carbon monoxide was supplied to the anode side humidified and heated to a dew point temperature equal to the cooling water inlet temperature. Air that has been humidified and heated to a dew point temperature equal to the cooling water inlet temperature is supplied to the cathode side.

The fuel cell was allowed to generate electricity continuously at a fuel utilization rate of 75%, an oxygen utilization rate of 20 to 80%, and a current density of 0.3 A/cm ² to measure output power performance over time. In addition, under the condition of a current density of 0.3A/cm ² , the cooling water flow rate was controlled during continuous power generation so that the temperature of the cooling water outlet was 7°C higher than that of the cooling water inlet.

Table 15 shows: the open circuit voltage of the battery under no load when the current is not output to the outside; the standard deviation (σ) of the voltage change of 100 unit cells for 100 hours after the start of continuous power generation; and after the start of continuous power generation The average rate of voltage drop (degradation rate) per hour for 10,000 hours.

Table 15 Oxygen utilization rate (%) Battery open circuit voltage (V) Voltage standard deviation (σ) Average speed of voltage drop (μv/h) 20 99 1.5 Impossible to work again after 9000 hours 30 98 1.5 4.3 40 98 1.6 1.8 50 98 1.7 1.8 60 98 1.8 1.6 70 97 2.1 1.5 80 96 5.3 7.8

It can be seen from Table 15 that although the open circuit voltage of the battery is not greatly affected by the oxygen utilization rate, when the oxygen utilization rate is 80%, the initial characteristic value σ increases under the influence of condensed water blockage in the gas flow channel. big. It was also seen that when the oxygen utilization rate was 20%, the battery voltage dropped to such an extent that the battery continued to work after 9000 hours. It can then be considered that the suitable oxygen utilization rate ranges from 30 to 70%.

Example 20

A fuel cell similar to the one in Example 1 was fabricated with the cooling water inlet temperature maintained at 65°C. A mixed gas containing 23% carbon dioxide, 76.5% hydrogen, 0.5% air, and 20 ppm carbon monoxide was supplied to the anode side humidified and heated to a dew point temperature equal to the cooling water inlet temperature. Air that has been humidified and heated to a dew point temperature equal to the cooling water inlet temperature is supplied to the cathode side.

The fuel cell was allowed to generate electricity continuously at a fuel utilization rate of 75%, an oxygen utilization rate of 50%, and a current density of 0.02 to 0.5 A/cm ² to measure output power performance over time. In addition, under the condition that the current density is not lower than 0.1A/cm ² , the cooling water flow rate is controlled during the continuous power generation process so that the temperature of the cooling water outlet is 6°C higher than the temperature of the cooling water inlet. Run the battery at a current density below 0.1A/cm ² so that the cooling water flow rate is equal to the flow rate at a current density of 0.1A/cm ² .

Table 16 shows: the open circuit voltage of the battery under no load when the current is not output to the outside; the standard deviation (σ) of the voltage change of 100 unit cells for 100 hours after the start of continuous power generation; and after the start of continuous power generation The average rate of voltage drop (degradation rate) per hour for 10,000 hours.

Table 16 Current density (A/cm ² ) Battery open circuit voltage (V) Voltage standard deviation (σ) Average speed of voltage drop (μv/h) 0.02 90 5.3 6.3 0.05 93 2.2 3.3 0.1 94 1.5 2.1 0.2 96 1.6 1.8 0.3 96 1.7 1.8 0.4 95 2.1 2.8 0.5 94 2.3 3.1

It can be seen from Table 16 that although the open circuit voltage of the battery is not greatly affected by the current density, when the current density is 0.02A/cm ² , under the influence of the flow rate reduction of the gas flowing along the gas flow channel, the initial The eigenvalue σ increases. It was also seen that the degradation rate increased when the current density was 0.02 A/cm ² . Therefore, it can be considered that the appropriate current density range is 0.05 A/cm ² or higher.

At the same time, the power generation voltage of each unit cell in the fuel cell is required to be maintained at not less than 0.7V in order to maintain a high level of power generation efficiency of the fuel cell stack. This requires that the current density is not higher than 0.3A/cm ² .

As described above, according to the present invention, a fuel cell having excellent performance and high durability can be realized while avoiding the flooding phenomenon caused by condensed water.

While this invention has been described in terms of presently preferred embodiments, it is to be understood that this disclosure is not to be construed as limiting. Various alterations and modifications will undoubtedly be obvious to those skilled in the art to which the present invention pertains after reading the above disclosure. Therefore, it is intended that the appended claims cover all such changes and modifications as fall within the spirit and scope of the invention.

It will be appreciated by those of ordinary skill in the art that changes may be made to the above-described embodiments without departing from the broad inventive principles of the invention. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.

Claims (10)

1. A fuel cell comprising a set of unit cells, each unit cell comprising: a hydrogen ion conductive electrolyte film; an anode and a cathode sandwiching the hydrogen ion conductive electrolyte film; an electron conductive separator located on the anode side and in contact with the anode; and located on the cathode side and in contact with the anode An electronically conductive separator in cathode contact, wherein: The electronically conductive separator on the anode side includes fuel gas passage grooves facing the anode for supplying fuel gas to the anode; The electron-conductive separator on the cathode side includes oxidant gas passage grooves facing the cathode for supplying oxidant gas to the cathode; and The equivalent diameter of the fuel gas channel groove and/or the oxidant gas channel groove is: each groove is not less than 0.79mm and not more than 1.3mm. 2. The fuel cell according to claim 1, wherein the depth of the fuel gas channel groove and/or the oxidant gas channel groove is not less than 0.7 mm and not greater than 1.1 mm. 3. The fuel cell according to claim 1, wherein the fuel gas passage groove and/or the oxidant gas passage groove: Follow a serpentine line extending from upstream to downstream; comprising a plurality of horizontal members parallel to each other and having substantially equal length "a"; and The ratio of the length "a" to the shortest linear dimension "b" between the most upstream horizontal member among the plurality of horizontal members and the most downstream horizontal member among the plurality of horizontal members satisfies the following relationship: a/ b≤1.2. 4. The fuel cell according to claim 1, wherein the fuel gas passage groove and/or the oxidant gas passage groove: follow a serpentine line extending from upstream to downstream; comprising a plurality of horizontal members parallel to each other and having substantially equal length "a"; and The ratio of the rib width "c" between the adjacent horizontal members to the length "a" satisfies the following relationship: 1/200≦c/a≦1/20. 5. The fuel cell according to claim 1, wherein each of said anode and said cathode comprises a gas diffusion layer and a catalytic reaction layer in contact with said gas diffusion layer, said anode and said cathode At least one of the gas diffusion layers has a thickness of about 100 to 400 μm. 6. The fuel cell according to claim 1, wherein each of said anode and said cathode comprises a gas diffusion layer and a catalytic reaction layer in contact with said gas diffusion layer, said anode and said cathode At least one of the gas diffusion layers has a gas permeability along a direction parallel to the main surface of the gas diffusion layer, with a permeability of 2×10 ^-8 to 2×10 ^-6 meters on a dry gas basis ² /(Pa·s) or so. 7. A method of operating a fuel cell as claimed in claim 1, wherein the pressure of at least one of the fuel gas flowing along the fuel gas passage groove and the oxidant gas flowing along the oxidant passage groove is The loss is not less than 1.5kPa and not more than 25kPa. 8. A method of operating a fuel cell as claimed in claim 1, wherein the ratio of the flow rate "f" of the underflow gas flowing into the anode to the flow rate "e" of the fuel gas flowing along the fuel gas flow groove The following relationship is satisfied: 0.05≤f/e≤0.43. 9. A method of operating a fuel cell as claimed in claim 1, wherein the ratio of the flow rate "h" of the underflow gas flowing into the cathode to the flow rate "g" of the oxidant gas flowing along the oxidant gas flow groove Satisfy the following relationship: 0.05≤h/g≤0.43. 10. A method of operating a fuel cell as claimed in claim 1, further comprising: providing the fuel cell with cooling medium channel grooves, wherein the inlet temperature of the cooling medium channel is about 45°C to 75°C, The dew point of at least one of the fuel gas and the oxidant gas to be supplied to the fuel cell is not lower than about -5°C and not higher than about +5°C, the dew point is related to the inlet temperature, so The utilization rate of the oxidant gas is not lower than 30% and not higher than 70%, and the power generation current density of the fuel cell is not lower than 0.05A/cm ² and not higher than 0.3A/cm ² .

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