WO2006109645A1

WO2006109645A1 - Solid electrolyte fuel cell and method for operating same

Info

Publication number: WO2006109645A1
Application number: PCT/JP2006/307213
Authority: WO
Inventors: Kenji Kobayashi; Shouji Sekino; Hideaki Sasaki; Satoshi Nagao; Takeshi Obata; Shin Nakamura; Tsutomu Yoshitake; Yoshimi Kubo
Original assignee: Nec Corporation
Priority date: 2005-04-08
Filing date: 2006-04-05
Publication date: 2006-10-19
Also published as: JPWO2006109645A1; JP5103905B2

Abstract

Disclosed is a solid electrolyte fuel cell comprising a solid polymer electrolyte membrane, a cathode arranged on one side of the solid polymer electrolyte membrane, an anode arranged on the other side of the solid polymer electrolyte membrane, a cathode collector and an anode collector respectively arranged on the cathode and anode, a fuel supply regulating membrane arranged on the anode collector for controlling supply of a liquid fuel to the anode, a perforated plate arranged on the fuel supply regulating membrane and having a plurality of holes for supplying the liquid fuel to the fuel supply regulating membrane, and an air vent formed between the fuel supply regulating membrane and the perforated plate.

Description

Solid oxide fuel cell and method of operating the same

Technical field

TECHNICAL FIELD [0001] The present invention relates to a solid electrolyte fuel cell using a solid polymer electrolyte membrane as an electrolyte membrane and using liquid fuel, and an operation method thereof.

Background art

[0002] Solid oxide fuel cells using liquid fuels are small and light-weight, so today, research and development as a power source for various electronic devices such as portable devices are being actively promoted. ing.

[0003] A solid electrolyte fuel cell includes an electrode electrolyte membrane assembly (MEA) having a structure in which a solid polymer electrolyte membrane is sandwiched between an anode and a force sword. A type of fuel cell that supplies liquid fuel directly to the anode is called a direct fuel cell. In the direct fuel cell, the supplied liquid fuel is decomposed on a catalyst supported on an anode to generate cations, electrons and intermediate products. Furthermore, in this type of fuel cell, the generated cations permeate the solid polymer electrolyte membrane and move to the force sword side, and the generated electrons move to the force sword side through an external load. The sword generates electricity by reacting with oxygen in the air. For example, in a direct methanol fuel cell (hereinafter referred to as DMFC) that uses an aqueous methanol solution as a liquid fuel, the reaction expressed by the following formula 1 occurs at the anode, and the reaction expressed by the following formula 2 is powerful. It happens in swords. As is clear from these equations 1 and 2, in DMFC, 1 mol of methanol and 1 mol of water react theoretically at the anode to produce 1 mol of reaction product (diacid-carbon). The At this time, since hydrogen ions and electrons are also generated, the theoretical concentration of methanol in the methanol aqueous solution, which is the fuel, is about 70 vol% in volume%.

[Chemical 1]

CH ₃ OH + H.0 → CO + 6H + + 6e "+ · + (1) 6H + + 6e + 3/20 ₂ → 3H ₂ 0 (2) Conventionally, however, when the amount of methanol supplied to the anode is relatively larger than the amount of water supplied, the methanol is expressed by the above equation 1. It is known that a “crossover” that permeates through the solid polymer electrolyte membrane without contributing to the reaction occurs, resulting in a decrease in power generation capacity and power generation. When the crossover increases, (0 output (potential) decreases, GO fuel consumption efficiency deteriorates, Gii) MEA temperature rises due to large calorific value, so fuel temperature rises more than necessary As a result, the crossover is further accelerated and a problem such as a further temperature rise is likely to occur.

[0004] The above crossover mainly occurs when a methanol aqueous solution (methanol aqueous solution having a high concentration of about 70 vol% or more) having a molar ratio of methanol to water of more than 1 is used. This occurs not only when using, but also when using a low-concentration methanol aqueous solution with a methanol concentration of, for example, less than 10 vol%. Although it is easy to reduce crossover by using a low-concentration methanol aqueous solution, the use of such a low-concentration methanol aqueous solution as a liquid fuel reduces the amount of power generated per unit mass of the liquid fuel. The problem arises that the energy density of the electrolyte fuel cell cannot be increased. Therefore, in order to obtain a solid oxide fuel cell with a high energy density, it is desirable to use a liquid fuel with a high concentration of raw fuel, such as a high-concentration aqueous methanol solution, while suppressing crossover.

[0005] As a DMFC technique for suppressing crossover, for example, Japanese Unexamined Patent Application Publication No. 2000-106201 (Document 1) includes a fuel vaporization layer that is stacked on an anode and supplies vaporized fuel.

A fuel cell including a fuel permeation layer that is laminated on the fuel vaporization layer and that supplies the supplied liquid fuel to the fuel vaporization layer is disclosed. According to the description in Patent Document 1,

"By vaporizing and supplying the fuel in this way, the gaseous fuel in the fuel vaporization layer is kept almost saturated, so the consumption of the gaseous fuel in the fuel vaporization layer due to the cell reaction is from the fuel permeation layer. The liquid fuel is vaporized and the liquid fuel is introduced into the cell by the capillary force, and the fuel supply amount is linked to the fuel consumption amount, so it is unreacted and discharged outside the battery. Like the conventional liquid fuel cell with almost no fuel Does not require a processing system. The effect is said to be!

That is, as shown in FIG. 1, the fuel permeable layer 106 for introducing liquid fuel into the cell by capillary force, and the anode 102 and the fuel permeable layer 106 are disposed between the fuel permeable layer 106 and the fuel permeable layer 106. A fuel vaporization layer 107 for vaporizing the introduced liquid fuel and supplying the fuel in the form of gas to the anode is laminated. By stacking a plurality of fuel permeation layers 106, fuel vaporization layers 107, and electromotive units 104 via separators 105, a stack 109 serving as a battery body is formed. The liquid fuel introduced into the liquid fuel introduction path 110 is supplied to the fuel permeation layer 106 by a capillary force from the side surface of the stack 109, further vaporized by the fuel vaporization layer 107, and supplied to the anode 102. Since the separator 105, the fuel permeation layer 106, and the fuel vaporization layer 107 also function as a current collector plate that conducts the generated electrons, for example, the fuel permeation layer 106 is formed of a carbon conductive material.

[0007] In this example, a 1: 1 mixture (molar ratio) of methanol and water is used as the fuel, and the fuel storage tank force is also supplied to the liquid fuel introduction path 110 by supplying the tank above the power generation unit. It may be configured such that the liquid fuel is pushed out by the natural fall caused by installation, the internal pressure in the tank, or the like, or the fuel can be drawn out by the capillary force of the liquid fuel introduction passage 110.

Disclosure of the invention

[0008] Upon further investigation of the configuration disclosed in Document 1, the present inventors have found that the following problems exist and cannot be stably generated as they are.

In other words, in the configuration in Document 1, a 1: 1 mixture (molar ratio) of methanol and water is used, and liquid fuel can be supplied to the fuel vaporization layer 107 by an internal pressure in the tank or the like. The present inventors have found that in the configuration of Patent Document 1, a stable fuel supply cannot be achieved by a product generated during a power generation operation. In other words, the reaction of Formula 1 above occurs at the anode, and the force that generates diacid-carbon is generated. The internal pressure on the anode side is increased by the generated diacid-carbon, and the supply of fuel with fuel vaporization strength is hindered. It is.

[0010] Furthermore, in the configuration in Document 1, it was also surprising that it was impossible to use a high-concentration methanol solution as fuel more than a 1: 1 mixture (molar ratio) of methanol and water as fuel. That is, since the vaporization supply amount of methanol is larger than the required amount of water, the above formula The anodic reaction of 1 is not performed smoothly.

[0011] The present invention has been made to solve the above-described problems, and an object of the present invention is to generate power using a higher concentration fuel in a DMFC including vaporization supply, which is advantageous for suppressing crossover. An object of the present invention is to provide a solid oxide fuel cell that can be made possible. Another object of the present invention is to provide an efficient operation method of such a solid oxide fuel cell.

[0012] A solid oxide fuel cell according to the present invention includes a solid polymer electrolyte membrane, a force sword disposed on one surface of the solid polymer electrolyte membrane, and an anode disposed on the other surface. A power sword current collector and an anode current collector disposed on the power sword and the anode, respectively, and a fuel that is disposed above the anode current collector and controls the supply of liquid fuel to the anode A supply suppression membrane, a perforated plate disposed above the fuel supply suppression membrane and having a plurality of holes for supplying liquid fuel to the fuel supply suppression membrane, the fuel supply suppression membrane, and the perforated plate A vent hole provided between the two.

[0013] According to the present invention, the fuel supply control film is disposed on the anode current collector between the anode current collector and the perforated plate. It acts to suppress the amount of permeation and can supply an optimal amount of fuel to the anode. In addition, according to the present invention, since a vent hole for the outside is provided between the solid polymer electrolyte membrane and the anode current collector, the vent force is reduced. It can be discharged to the outside. Since the internal pressure does not increase due to the effective discharge of carbon dioxide, the fuel supply from the fuel supply suppression membrane to the anode can be prevented from being hindered. In addition, since the vent can take in oxygen into the anode, the taken-in oxygen can react with the catalyst supported on the anode and store water in the anode in advance. The presence of this water has the remarkable effect that power generation is possible even when a 100% methanol solution is used as the liquid fuel.

[0014] In the above solid oxide fuel cell, a spacer having a sealing function and provided between the solid polymer electrolyte membrane and the anode current collector is provided. It is preferable that the vent hole is provided in the spacer.

[0015] A vent is provided in a spacer provided between the solid polymer electrolyte membrane and the anode current collector. It is convenient in terms of structure.

[0016] The solid oxide fuel cell preferably further includes an evaporation suppression layer provided on the force sword current collector.

[0017] According to the present invention, since the evaporation suppression layer is provided on the force sword current collector, evaporation of water generated in the cathode can be prevented. The water whose evaporation is suppressed can be back-diffused to the anode side to cause a power generation reaction with a 100% methanol solution.

[0018] In the above solid oxide fuel cell, it is preferable that a gap is provided between the fuel supply suppressing membrane and the anode. Further, it is preferable that the vent hole is provided so as to communicate the gap and the outside!

[0019] According to the present invention, since there is a gap between the fuel supply suppression membrane and the anode, oxygen having a sufficient ventilation capacity is supplied to the entire anode, and water can be efficiently generated. M

The heat generated in the EA (electrode-electrolyte membrane assembly) is less likely to be transferred to the fuel tank side, so the effect of preventing the fuel temperature from rising can be obtained.

[0020] In the above-described solid oxide fuel cell, it is desirable that the fuel supply suppression membrane is sandwiched and fixed between the perforated plate and the anode current collector.

[0021] In the above solid oxide fuel cell, the liquid fuel includes methanol and water.

The ratio of the number of moles of methanol (Mm) to the number of moles of water (Mw) is preferably MmZMw> 1.

[0022] The liquid fuel in which the ratio of the number of moles of methanol (Mm) to the number of moles of water (Mw) is MmZMw> 1 can be continuously used for the following reason. In other words, it was confirmed that if power generation is continued using 100% methanol, the initial generated water is consumed, but stable power generation is still possible. This is presumably because the water generated by the power generation reaction of the power sword is diffused back to the anode side, so that the water necessary for the anode reaction is sufficiently supplied even if water is not supplied as fuel.

[0023] A solid oxide fuel cell according to the present invention is an operation method of the solid oxide fuel cell. A step of supplying an oxidant to the fuel cell in an initial state or a rest state, a step of starting fuel supply, and a step of starting energization to an external load after the cell potential reaches a predetermined potential. [0024] According to the present invention, when the initial state or the resting state force is operated, water is sufficiently generated at the anode by supplying the oxidant and the fuel without first energizing. By passing a subsequent step of energizing and starting power generation, stable power generation can be continued even if high concentration liquid fuel exceeding the theoretical value, such as 100% methanol, is supplied.

[0025] According to the solid oxide fuel cell of the present invention, the fuel supply control membrane acts so as to suppress the fuel permeation amount to the anode, so that an optimum amount of fuel can be supplied to the anode and stable. Power generation can be continued. Furthermore, since the vents act to discharge carbon dioxide generated during power generation to the outside, carbon dioxide carbon dioxide is effectively discharged. As a result, it is possible to stabilize the fuel supply from the fuel supply suppression membrane to the anode while preventing an increase in internal pressure. In addition, since the oxygen can be taken into the anode through the vent hole, the taken-in oxygen reacts with the catalyst supported on the anode, so that water can be stored in the anode in advance. The presence of this water in the solid oxide fuel cell of the present invention has a remarkable effect that power generation is possible even when a 100% methanol solution is used as the liquid fuel.

Brief Description of Drawings

FIG. 1 is a diagram showing an example of a conventional vaporization supply type DMFC.

FIG. 2 is a schematic cross-sectional view showing an example of a cell structure of a solid oxide fuel cell of the present invention.

FIG. 3 is a schematic perspective view showing a structural arrangement from an MEA to a perforated plate.

FIG. 4A is a schematic diagram showing an example of a vent hole provided between a solid polymer electrolyte membrane and an anode current collector.

FIG. 4B is a schematic view showing an example of a vent hole provided between the solid polymer electrolyte membrane and the anode current collector.

FIG. 4C is a schematic view showing an example of a vent hole provided between the solid polymer electrolyte membrane and the anode current collector.

FIG. 5 is a graph showing the film thickness dependence on the methanol permeation rate of the fuel supply suppression membrane used in the examples.

[Fig. 6] A one-hour change in potential was shown when power was generated for 10 hours using the DMFC structure of the present invention. It is a graph.

FIG. 7A is a plan view showing a spacer constituting the solid oxide fuel cell of Example 1.

FIG. 7B is a plan view showing a perforated plate constituting the solid oxide fuel cell of Example 1. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the solid oxide fuel cell and the operation method thereof according to the present invention will be described with reference to the drawings. FIG. 2 is a schematic cross-sectional view showing an example of the cell structure of the solid oxide fuel cell of the present invention, and FIG. 3 is a schematic oblique view showing an outline of the arrangement from the MEA to the perforated plate. 4A to 4C are schematic views showing the form of vents provided between the solid polymer electrolyte membrane and the anode current collector. The present invention is not limited to these drawings and the embodiments described below.

[0028] (Solid oxide fuel cell)

The solid oxide fuel cell of the present invention includes a solid polymer electrolyte membrane 11, a force sword 12 disposed on one surface of the solid polymer electrolyte membrane 11 in contact with the surface, and a force sword 12 disposed on the other surface. At least a power sword 12 and a power sword current collector 14 and an anode current collector 15 disposed on and in contact with the anode 13, respectively, and are supplied with liquid fuel. It is a solid oxide fuel cell having a cell structure 10 (hereinafter simply referred to as “cell” or “cell structure”).

[0029] The solid polymer electrolyte membrane 11, the force sword 12 and the anode 13 constitute an MEA (electrode-electrolyte membrane assembly; Membrane and Electrode Assembly). On the upper and lower surfaces of the MEA, a force sword current collector 14 and an anode current collector 15 are pressed with spacers 21 and 22 sandwiched, respectively. The solid polymer electrolyte membrane 11 is not particularly limited, but commercially available ones used in the examples described later can also be used. Both the force sword 12 and the anode 13 sandwiching the solid polymer electrolyte membrane 11 from both sides are produced by applying a catalyst paste containing carbon particles carrying a catalyst onto, for example, carbon paper as a porous substrate. Is done. The produced force sword 12 and the anode 13 are disposed and pressure-bonded so that the catalyst paste layer side is on the solid polymer electrolyte membrane 11 side, thereby producing the MEA. In FIG. 2, the solid polymer electrolyte membrane 11, the force sword 12 and the anode 13 are denoted by reference numerals as constituting the MEA. For the power sword 12 and anode 13 shown, the layer on the solid polymer electrolyte membrane 11 side represents the catalyst paste layer (no symbol), and on the side away from the solid polymer electrolyte membrane 11 force. A layer represents the porous substrate (no symbol).

[0030] The greatest feature of the present invention is that the anode current collector 15 has a fuel supply suppressing membrane 17 disposed between the anode current collector 15 and the perforated plate 16, and a solid polymer electrolyte. The vent hole 31 (see FIGS. 4A to C) is provided between the membrane 11 and the anode current collector 15.

In the solid oxide fuel cell of the present invention, a fuel supply suppression film 17 is provided between the anode current collector 15 and the perforated plate 16. The fuel supply suppression film 17 is a control film that vaporizes the fuel and controls the supply thereof, and acts to suppress the fuel permeation amount to the anode 13. As a result, an optimal amount of fuel can be supplied to the anode 13, and stable power generation can be continued. The fuel is supplied from the fuel tank 18 through the perforated plate 16 to the fuel supply suppressing film 17.

[0032] The fuel supply suppressing film 17 is sandwiched and fixed by an anode current collector 15 having an opening for supplying the anode 14 without interfering with fuel and a perforated plate 16 such as a punching sheet. Yes. For this reason, it is not necessary to pressurize and fix by a fuel holding layer called a wicking material or the like as in the prior art.Also, by setting the thickness according to the fuel concentration, the methanol permeation rate that permeates the fuel supply suppression membrane 17 is increased. It can be easily adjusted to supply the optimum amount of methanol.

[0033] As the fuel supply suppression membrane 17, an electrolyte membrane (styrene dibulebenzene membrane) is used. Further, the film thickness is set according to the fuel concentration to be used. The styrene dibule benzene film is a sulfonated styrene dibule benzene copolymer. The amount of fuel supplied to the fuel supply suppression membrane 17 must be equal to or greater than the amount of methanol consumed in the MEA (electrode-electrolyte membrane assembly). Determined by area. The opening area can be easily controlled by holding the fuel supply suppression membrane 17 between, for example, two perforated plates 16.

The perforated plate 16 is provided closer to the fuel tank 18 than the fuel supply suppressing film 17. The perforated plate 16 has a plurality of holes for supplying the fuel solution to the fuel supply suppressing membrane 17. The As described above, the perforated plate 16 may be provided so as to sandwich the fuel supply suppressing film 17 as necessary. The perforated plate 16, together with the anode current collector 15, prevents the membrane from being greatly deformed due to swelling of the fuel supply suppression membrane 17, an increase in internal pressure due to gas generation at the anode, and excessive stress is applied. Acts to prevent As the material of the perforated plate 16, as long as it has methanol resistance and has a certain degree of hardness, for example, SUS or the like is used. By using a perforated plate, it is possible to make a structure having a gap 27 between the fuel supply suppressing membrane 17 and the anode 13. This makes it difficult for the heat generated by the MEA (electrode-electrolyte membrane assembly) to be transmitted to the fuel tank 18 side, thereby suppressing an increase in fuel temperature and enabling stable power generation.

In the solid oxide fuel cell of the present invention, a plurality of spacers having a sealing function are provided in each part of the cell structure 10. For example, as shown in FIGS. 2 and 3, (a space between the solid polymer electrolyte membrane 11 and the force sword current collector 14 having a thickness approximately the same as the thickness of the force sword 12. Is provided at the periphery of the cell structure 10. Between the GO solid polymer electrolyte membrane 11 and the anode current collector 15, a spacer 22 having a thickness substantially the same as the thickness of the anode 13 is provided. (Iii) A spacer 23 having a sealing function is provided on the periphery of the cell structure 10 between the anode current collector 15 and the fuel supply suppressing film 17, and (iii) iv) A spacer 24 having a sealing function is provided on the periphery of the cell structure 10 between the fuel supply suppressing membrane 17 and the perforated plate 16, and (V) the perforated plate 16 and PP, for example, A spacer 25 with a sealing function is provided on the periphery of the cell structure 10 between the fuel tank 18 and the plastic material. Is. Note that each of these spacer scratch, typically is formed of a silicon rubber or plastic or the like having a sealing function.

The present invention is characterized in that a vent hole is provided between the solid polymer electrolyte membrane 11 and the anode current collector 15. The vent hole communicates with the outside. The air hole can achieve the effect of the present invention regardless of the form provided as long as it is provided between the solid polymer electrolyte membrane 11 and the anode current collector 15. It is preferable that the spacer 22 provided between the polymer electrolyte membrane 11 and the anode current collector 15 is provided with a vent hole 31 which is a characteristic configuration of the present invention. The vent hole 31 is provided in the spacer 22, and thereby, the two generated during power generation in the catalyst paste layer of the anode 13. The carbon oxide passes through the porous substrate holding the catalyst paste layer directly or once after exiting the void 27, and is discharged from the air holes 31 of the spacer 22 arranged at the periphery of the anode 13. Is done. In the present invention, this vent hole 31 effectively discharges carbon dioxide and carbon, so that an increase in internal pressure in the cell can be prevented, and the fuel supply suppression membrane 17 to the anode 13 It can prevent that the fuel supply to is interrupted. In addition, the vent 31 can also take in oxygen into the external force anode 13. The taken-in oxygen and the supplied fuel react on the catalyst supported on the anode 13 as shown in the following formula 3, and water can be stored in advance in the anode. According to the experiments by the present inventors, it was confirmed that power generation was possible even when a 100% methanol solution was used as the liquid fuel.

[Chemical 3]

1/2 CH ₃ OH + 3/40 ₂ → 1/2 C0 ₂ + H ₂ 0… (3)

[0037] If power generation is continued using a 100% methanol solution, the initial generated water is consumed.

1S It has been confirmed by experiments by the present inventors that the power generation is still stable. This is presumably because the water generated by the power generation reaction of the power sword is diffused back to the anode side, and sufficient water necessary for the anode reaction is supplied even if water is not supplied as fuel. Since the reverse diffusing water also wets the solid polymer electrolyte membrane, it can prevent a decrease in proton conductivity and contribute to stable operation.

[0038] As a result of the discovery of such a new power generation mechanism by the present inventors, the liquid fuel contains methanol, and the ratio of the number of moles of methanol (Mm) to the number of moles of water (Mw) is Mm ZMw. It is possible to suitably use those that are> l. In particular, as described above, even when a 100% methanol solution containing no water is used, power generation can occur and the power generation can be continued. It is preferable that the vent hole 31 is provided at a position where oxygen for generating water required at the initial stage in the anode is supplied and the generated by-product (carbon dioxide) can be efficiently removed. For example, as shown in FIGS. 4A to 4C, the spacer 22 provided between the anode current collector 15 and the solid polymer electrolyte membrane 11 may be provided by fragmentation or the like (A). The spacer 22 may be provided with a rectangular cut so that it is uneven! (B), or a form (C) with a through-hole that traverses the inside of the spacer 22 may be used. , Structure that has the same effect If it is, it will not specifically limit. Examples of the material of the spacer 22 forming the vent hole 31 include silicon rubber and plastic. 4A to 4C, the air holes 31 may be provided on all four sides, showing an example in which the air holes 31 are formed on only two opposite sides.

The vent 31 can be opened and closed to prevent oxygen and water from reacting in the anode during storage in the initial state before operation or in the rest state when operation is stopped. It is preferable to do. Also, during storage, it is preferable to take measures such as providing a shutter mechanism or at least emptying the fuel flow path so that methanol does not permeate the fuel supply suppression membrane 17! /.

[0039] Conventionally, in DMFC, it is known that water leakage due to water generated on the force sword side is a problem. In the present invention, water generated on the force sword side is reversely diffused to the anode side. Therefore, it is necessary to prevent water evaporation in the force sword 12. Therefore, it is preferable to provide the evaporation suppression layer 19 on the force sword current collector 14.

As a moisturizing method using the evaporation suppression layer 19, for example, (0 a method of directly moisturizing an evaporation suppression layer made of a hydrophilic material on a force sword, (ii) closing the force sword with an evaporation suppression layer made of a water repellent material, (M) The above (method of moisturizing a combination of 0 and GO, etc.), etc. (The material for the evaporation suppression layer 19 suitable for the above method 0 is a fiber mat. , Hydrophilic cellulose fibers, glass fibers, etc., and the material of the evaporation suppression layer 19 suitable for the above method (ii) includes meta-resistant plastic materials (PTFE, ET FE, polypropylene, polyethylene, etc.) ), Metal mats, etc. The material of the evaporation suppression layer 19 preferably has resistance to methanol.

[0040] Such an evaporation suppression layer 19 has an effect of preventing moisture evaporation and keeping moisture. A cover member 20 may be further provided on the evaporation suppression layer 19 (see FIG. 2). The cover member 20 can take in air necessary for power generation by adopting a structure in which the side force air is taken in or a structure in which a hole is formed in the cover member 20 itself. As a result, it is possible to suppress excessive evaporation of the generated water from the force sword while restricting the vent hole 31 that is an air intake port to the necessary minimum.

In the present invention, as shown in FIG. 2, there is a space between the fuel supply suppression membrane 17 and the anode 13. A gap 27 may be provided. Due to the presence of the air gap 27, oxygen from the vent hole 31 is supplied to the entire anode, and water can be efficiently generated. In addition, the heat generated by the MEA can be made difficult to transfer to the fuel tank, and the effect of preventing the fuel temperature from rising can be obtained.

As described above, according to the solid oxide fuel cell of the present invention, there is a remarkable effect that power generation is possible even when a 100% methanol solution is used as the liquid fuel.

[0042] (Operation Method of Solid Oxide Fuel Cell)

An operation method of the solid oxide fuel cell of the present invention is an operation method of the solid oxide fuel cell according to the present invention, comprising: supplying an oxidizing agent to the fuel cell in an initial state or a resting state; It includes a step of starting fuel supply and a step of starting energization to an external load after the cell potential reaches a predetermined potential. First, an oxidant is supplied to the fuel cell in the initial state or the resting state. The oxidant is oxygen (including oxygen in the air; hereinafter referred to as air). If the air gap 27 is formed in advance, the air present in the air gap is supplied as the oxidant. . On the other hand, when no gap is formed, the air that has entered through the vent hole 31 is supplied as an oxidant.

Next, fuel is supplied from the fuel cartridge device or the fuel tank 18. The fuel supplied from the fuel tank 18 passes through the perforated plate 16 and is vaporized by the fuel supply suppressing film 17 to be supplied to the anode. In the present invention, since the oxidizing agent is already supplied to the anode before the fuel is supplied, when the fuel is supplied to the anode, the oxidant and the fuel are separated on the catalyst supported on the anode. The water reacts as shown in Equation 3 above.

Next, the cell potential is confirmed, and energization to the external load is started after the cell potential reaches a predetermined potential. The confirmation of the cell potential is to confirm that sufficient water is generated. The cell potential is confirmed to confirm that the generated electromotive force reaches a predetermined value, and then energization to the external load is started. In the present invention, for example, when 100% methanol is supplied as fuel, power generation proceeds without supplying water as fuel. Thought to be despread to the side. As a result, power generation proceeds even if water is not supplied. [0044] According to such an operation method, stable power generation can be continued even when a high-concentration liquid fuel exceeding the theoretical value, such as 100% methanol, is supplied.

Example

[0045] The solid oxide fuel cell of the present invention will be specifically described below by showing experimental examples.

FIG. 5 is a graph showing the dependence of the fuel supply suppression membrane used in this example on the membrane permeation rate. As the fuel supply suppression membrane, a styrene dibenzene-based membrane with a changed film thickness is used. One of the fuel supply suppression membranes is on the methanol side and the other is open to the atmosphere. Asked. The fuel consumption (methanol permeation rate) is known to be proportional to the current density. For example, in this example, when the MEA methanol permeation rate was 0. OlgZhZcm ² , the fuel supply suppression membrane methanol permeation rate is desired is 0. 0 2~0. 03gZhZcm ² is twice to three times the methanol permeation rate of MEA. If the methanol permeation rate is too high, crossover will occur, and if stable power generation cannot be achieved, the force or energy density will decrease. On the other hand, if the methanol permeation rate is too low, the amount of fuel supply is insufficient and power generation itself cannot be performed. In the case of the styrene divinylbenzene film used in this example, the range of 100 to 135 / ζ πι is appropriate considering the methanol permeation rate in FIG.

[0046] The cell structure used in this example will be described below. First, catalyst-supported carbon particles are prepared by supporting 50% by weight of white metal particles having a particle diameter in the range of 3 to 5 nm on carbon particles (Ketjen Black EC600JD manufactured by Rion Co., Ltd.). An appropriate amount of 5% by weight Nafion solution (trade name; DE521, “Nafion” is a registered trademark of DuPont) manufactured by DuPont was added to the carbon fine particle lg and stirred to obtain a catalyst base for forming a force sword. . This catalyst paste was applied to a carbon paper as a base material (TGP-H-120 manufactured by Torayen clay) at a coating amount of 8 mgZcm ² and dried to prepare a 4 cm × 4 cm force sword sheet. On the other hand, the above catalyst for forming a cathode except that platinum (Pt) -ruthenium (Ru) alloy fine particles (Ru ratio is 50 at%) having a particle diameter in the range of 3 to 5 nm are used instead of platinum fine particles. The catalyst paste for anode formation should be the same as the conditions for obtaining the paste. Obtained. Except for the use of this catalyst paste,

- to prepare a de ₀

[0047] Next, an 8 cm x 8 cm x 180 m thick membrane made of DuPont's Naphion 117 (number average molecular weight is 250000) was used as the solid polymer electrolyte membrane 11, and one side of the thickness direction of this membrane was The force sword was placed on the surface of the carbon paper so that the carbon paper faced outward, and the anode was placed on the other face of the carbon paper so that the carbon paper faced outward. The external force of each carbon paper was also hot pressed. As a result, the force sword 12 and the anode 13 were joined to the solid polymer electrolyte membrane 11 to obtain MEA (electrode-electrolyte membrane assembly).

[0048] Next, on the force sword 12 and the anode 13, current collectors 14 and 15 made of stainless steel (SUS316) made of stainless steel (SUS316) having an outer dimension of 6 cm ² , a thickness of 1 mm, and a width of 11 mm and having a rectangular frame shape are provided. Arranged. In addition, a vent 31 made of a rectangular frame-shaped frame plate made of silicon rubber and having an outer dimension of 6 cm, a thickness of 0.3 mm, and a width of 10 mm was formed between the solid polymer electrolyte membrane 11 and the anode current collector 15. Pacer 22 was placed. In this spacer 22, a vent hole 31 for discharging carbon dioxide and carbon dioxide was used in which eight incisions with a width of 0.5 mm were provided at two locations on each side of the frame (see FIG. 7A). ). Further, a spacer 21 having a sealing function between the solid polymer electrolyte 11 and the force sword current collector 14 was disposed. This spacer 21 and other spacers 23, 24, and 25 (see Fig. 2) are made of silicon rubber and have a rectangular frame shape with an outer dimension of 6 cm ² , a thickness of 0.3 mm, and a width of 10 mm. A spacer having a sealing function was used.

[0049] An 8 cm x 8 cm x 125 / zm fuel supply suppression membrane 17 made of the above-mentioned styrene dibutene benzene membrane (ion exchange capacity 1.9 mmolZg, water content 13%) is prepared. Arranged on the anode current collector 15 side. In addition, a perforated plate 16 (see Fig. 7B) of SUS316 stainless steel with an outer dimension of 6 cm ² , a thickness of 1 mm, a hole diameter of 4 mm, and an opening ratio of 60% is prepared. Arranged on the 17th side. Furthermore, a fuel tank 18 was provided adjacent to the perforated plate 16. The fuel tank 18 is a container made of PP and having an outer dimension of 6 cm ² , a height of 8 mm, an inner dimension of 44 mm ² , and a depth of 3 mm. A fuel supply port 18a for supplying fuel is provided on the side of the tank. Inside, there is a wicking material made of urethane as a fuel retention material.

On the other hand, an evaporation suppression layer 19 made of a fiber mat was provided above the force sword. This evaporation Suppressing layer 19, which functions as a moisture retaining layer, cellulose was processed into ² square 35mm textiles sheet (cotton fibers wiper member BEMCOT, manufactured by Asahi Kasei Corporation) Place, as the cover member 20 thereon, the thickness 0 A PTFE punching sheet having a hole diameter of 5 mm and a hole diameter of 0.75 mm and an opening ratio of 60% was placed thereon, and the evaporation suppression layer 19 was fixed.

[0051] Of these members, members other than the cover member 20 are screwed and integrated with the cell frame 29. In addition, the screw used at this time is a screw made of grease to prevent leakage. In this way, the MEA, the force sword current collector, the anode current collector, the fuel supply suppression film, the seal member, the evaporation suppression layer, etc. are integrated together by a predetermined number of screws, and the solid electrolyte type having the cross-sectional structure shown in FIG. A fuel cell was obtained.

FIG. 6 shows a solid oxide fuel cell obtained as described above, using pure methanol (100% methanol) as the fuel at room temperature (25 ° C.) and 0.3 A (about 19 mAZcm ² ). It is the graph which showed the time change of the potential when generating electricity for 10 hours. Figure 6 shows that power generation is stable for 10 hours. The fuel consumption at this time was 0.185 gZh (about 0.012 g ZhZcm ² ), and the energy density per weight was 0.52 WhZg. The reason why the fuel consumption is smaller than the value of the fuel supply suppression membrane alone (equivalent to 100 m) is that the amount of fuel permeation suppressed by MEA is included.

Claims

The scope of the claims

[1] a solid polymer electrolyte membrane;

A force sword disposed on one surface of the solid polymer electrolyte membrane;

An anode disposed on the other surface;

A force sword current collector and an anode current collector respectively disposed on the force sword and the anode;

A fuel supply suppression membrane disposed above the anode current collector and controlling supply of liquid fuel to the anode;

A perforated plate disposed above the fuel supply suppression membrane and having a plurality of holes for supplying liquid fuel to the fuel supply suppression membrane;

A vent hole provided between the solid polymer electrolyte membrane and the perforated plate,

Solid electrolyte fuel cell.

[2] A solid oxide fuel cell according to claim 1, comprising:

Furthermore,

A spacer having a sealing function and provided between the solid polymer electrolyte membrane and the anode current collector;

Comprising

The vent hole is provided in the spacer.

Solid electrolyte fuel cell.

[3] A solid oxide fuel cell according to claim 1 or 2, comprising:

Furthermore,

Evaporation suppression layer provided on the force sword current collector

With

[4] The solid oxide fuel cell according to any one of claims 1 to 3, wherein a gap is provided between the fuel supply suppression membrane and the anode.

Solid electrolyte fuel cell.

[5] The solid oxide fuel cell according to claim 4, The air hole is provided so as to allow the air gap to communicate with the outside, and is a solid oxide fuel cell.

[6] The solid oxide fuel cell according to any one of claims 1 to 5, wherein the fuel supply suppression membrane is sandwiched and fixed between the perforated plate and the anode current collector. ing

Solid electrolyte fuel cell.

[7] The solid oxide fuel cell according to any one of claims 1 to 6, wherein the liquid fuel includes methanol and water,

A solid oxide fuel cell in which the ratio of the number of moles of methanol (Mm) to the number of moles of water (Mw) is MmZMw> 1.

[8] A method for operating a solid oxide fuel cell according to any one of claims 1 to 7,

Supplying an oxidant to the fuel cell in an initial state or a resting state; starting the fuel supply;

Starting energization to an external load after the cell potential reaches a predetermined potential, and

Operation method of solid oxide fuel cell.