JPH0866632A - Anode electrode catalyst for high-molecular solid electrolytic type fuel cell - Google Patents

Abstract

PURPOSE: To prevent substantially influence from carbon monoxide poisoning. CONSTITUTION: An anode electrode catalyst for a fuel cell comprises at least one kind of 1-70 atom% nickel, cobalt, manganese and gold, and an alloy of at least one kind of metals of platinum, palladium and ruthenium. When this catalyst is used as the anode of the fuel cell and operated by supplying a fuel containing about 100 ppm carbon monoxide, a bad influence from poisoning is almost not observed. As the carbon monoxide amount contained in the fuel produced by usual modification of methanol and a shift reaction that follows can be controlled relatively easily to about 100 ppm, the produced fuel can be used as it is without further purification.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrocatalyst which is used as an anode of a fuel cell and which comprises an alloy of at least one of nickel, cobalt and manganese and a noble metal.

[0002]

2. Description of the Related Art Electrochemical cells, such as polymer electrolyte fuel cells, are attracting attention as a power source for electric vehicles and spacecraft because they are more compact and have higher current densities than phosphoric acid fuel cells. . Also, in the development of this field, various electrode structures, catalyst production methods, system configurations, etc. have been proposed. The conventional fuel cell electrode structure is, for example, a collector for cathode / cathode /
It has a five-layer sandwich structure of polymer solid electrolyte (ion exchange membrane) / anode / collector for anode.

The fuel supplied to this fuel cell is produced, for example, by reforming methanol, and this fuel contains carbon dioxide and carbon monoxide in addition to hydrogen. Conventionally, carbon black supporting a catalyst and polytetrafluoroethylene (hereinafter referred to as PT) are used as the anode of the fuel cell.
A powder mixture of FE) formed on a gas-permeable carbon non-woven paper in layers is generally used. However, this anode catalyst is often poisoned by carbon monoxide contained in the fuel during low-temperature operation, and its catalytic activity is often greatly reduced.

In order to avoid this drawback, it is desirable to use pure hydrogen as a fuel, but not only is pure hydrogen expensive, but also its storage is costly and easily scattered from the storage tank to the atmosphere for a long time. Not easy to store for a period. If carbon monoxide is removed from the methanol reformed fuel, the problem of poisoning does not occur as in the case of pure hydrogen supplied from the tank, but the cost is high as in the case of using pure hydrogen. Actually, it is almost impossible to completely remove carbon monoxide even by multi-step treatment. In the past, avoiding poisoning of fuel cell electrodes by carbon monoxide has been of utmost concern in the field, and the poisoning has been a serious obstacle to the practical application of fuel cells, and various electrode materials Despite the proposal, a fuel cell electrode having sufficient resistance to poisoning has not been developed yet. The present inventor has made an anode electrode catalyst for a fuel cell, which is composed of an alloy of tin and a noble metal having excellent poisoning characteristics (Japanese Patent Application No. 6-23776).
No.) and an alloy of a noble metal with germanium and / or molybdenum and an anode electrode catalyst for a fuel cell (Japanese Patent Application No. 6-
114638) was proposed.

[0005]

OBJECTS OF THE INVENTION It is an object of the present invention to provide an electrode catalyst having an activity equivalent to that of the tin-noble metal catalyst and the germanium-molybdenum-noble metal catalyst.

[0006]

The present invention comprises an alloy of 1 to 70 atomic% of at least one of nickel, cobalt, manganese and gold and at least one metal of platinum, palladium and ruthenium. The present invention is an anode electrode catalyst for a polymer electrolyte fuel cell.

The details of the present invention will be described below. The anode electrode catalyst for polymer electrolyte fuel cells according to the present invention comprises 1 to 70 atomic% of at least one of nickel, cobalt, manganese and gold and at least one noble metal of platinum, palladium and ruthenium. The alloy in the present invention includes an amorphous alloy, a solid solution, and an intermetallic compound in addition to a normal alloy. Therefore, the electrode catalyst according to the present invention is not only obtained by melt-mixing at least one of nickel, cobalt, manganese and gold and a noble metal and further cooling, but also Co _a Ni _b
Mn _c Au _d Me _e (where Me is platinum, palladium or ruthenium, and 0 ≦ a, b, c, d <1, 0 <e
An intermetallic compound represented by <1) can be prepared and used as it is.

In the electrocatalyst of the present invention, if the atomic% of at least one of nickel, cobalt, manganese and gold is less than 1%, there is almost no effect of preventing poisoning of the noble metal catalyst. When the cation exchange membrane, which is a molecular solid electrolyte, is of an acid type, nickel and the like are likely to be eluted into the electrolyte, and the absolute amount of the noble metal, which is the main catalyst substance, is insufficient and the catalytic activity is reduced. The noble metal used in the present invention is selected from platinum, palladium and ruthenium, and each metal is used alone or in combination, and a particularly preferred noble metal is platinum. Usually nickel, cobalt,
At least one component of manganese and gold is added to these noble metals to form an alloy catalyst, but other components such as tin, germanium and molybdenum may be contained in a slight amount.

The reason why carbon monoxide poisoning is suppressed by adding nickel or the like to a combination of a noble metal and at least one of nickel, cobalt, manganese, and gold, that is, a noble metal catalyst, has not been clarified. The adsorption site is occupied by nickel or the like to reduce the amount of adsorbed carbon monoxide, or the adsorption itself is prevented, and nickel or the like functions as an oxidation catalyst to oxidize carbon monoxide once adsorbed to carbon dioxide. It is speculated that it is a synergistic effect of both of removing carbon. Although it depends on the amount of nickel, etc., when the fuel cell is operated using the electrode catalyst of the present invention, even if the fuel supplied contains about 100 ppm of carbon monoxide, the catalytic activity is lowered to such an extent. The catalyst is hardly poisoned and stable operation can be continued.

In order to incorporate the above catalyst into a fuel cell as an anode, for example, a conventional carrier such as carbon black is loaded with a first metal by a thermal decomposition method or the like, and then a second metal is further loaded to form an alloy. Ionic resin, PT
It is formed as a thin film or a porous body on FE or the like on a substrate or an electrolyte membrane, and it is fixed at a predetermined position of the fuel cell, or the produced alloy is sputtered to form a thin film of the alloy on the substrate or the electrolyte membrane. The substrate or the electrolyte membrane with alloy catalyst is placed together with the current collector at a predetermined position of the fuel cell.

The cathode, which is the counter electrode of the fuel cell, is not particularly limited, and conventional electrodes such as those prepared by mixing catalyst-supporting carbon black and PTFE powder and supporting them on a substrate and firing them may be used. . Since the anode of the fuel cell produced in this manner is composed of the electrode catalyst of the present invention, as described above, even if the fuel contains carbon monoxide of about 100 ppm, the operation is hardly affected. Absent. Since the carbon monoxide content in the fuel produced by methanol reforming can be reduced to 100 ppm relatively easily, the produced fuel can be used as it is without further purification. .

[0012]

[Examples] Examples of anode electrode catalysts for polymer solid oxide fuel cells according to the present invention will be described below.
This example does not limit the present invention.

Example 1 A platinum and nickel target was simultaneously subjected to argon sputtering on a glass plate with a lead terminal having a diameter of 10 mm in a chamber under reduced pressure to form a platinum-nickel alloy thin film having a thickness of 0.5 μm. This was fixed to one end surface of a stainless steel rod having a diameter of 8 mm and attached to a rotary electrode device.

A rotating electrode of platinum: nickel = 76: 24 (atomic%) was immersed in a 0.1 M aqueous solution of perchloric acid, and hydrogen containing 100 ppm of carbon monoxide was bubbled for 1 hour for poisoning. While bubbling was continued, the change with time of the current of the rotating electrode was measured while rotating at 1500 rpm with the platinum electrode as the counter electrode. The result is shown in FIG. It can be seen from Fig. 1 that the current obtained is almost unchanged with the lapse of operating time and is constant at about 2.1 mA.

[0014]

Example 2 A rotating electrode was produced in the same manner as in Example 1 except that the atomic ratio of platinum: nickel was set to 58:42. Using this rotating electrode, the change in current with time was measured under the same conditions as in Example 1. The result is shown in FIG. FIG.
It can be seen that although the current obtained from the above is smaller than that in Example 1, it is almost unaffected by the passage of operating time and is constant at about 1.9 mA.

[0015]

Comparative Example 1 A rotary electrode was manufactured in the same manner as in Example 1 except that plain platinum was used instead of the platinum-nickel alloy. Using this rotating electrode, the change with time of the current was measured under the same conditions as in Example 1 except that the poisoning carbon monoxide on the electrode surface was desorbed immediately before the start of current measurement. The result is shown in FIG. The initial value of the current obtained from Fig. 1 is 5.
Although it is as large as 0 mA, it can be seen that the current obtained is deactivated in a short time and the obtained current becomes zero after 15 minutes.

[0016]

Example 3 A palladium-nickel alloy was produced in the same manner as in Example 1 except that platinum was replaced with palladium, and a rotating electrode was produced using the alloy to produce 100% carbon monoxide.
Using hydrogen containing ppm as a fuel, the change with time of the current of the rotating electrode was measured. Although the obtained current was slightly smaller than the rotating current of Example 1, a stable current could be taken out for a long period of time.

[0017]

Example 4 A ruthenium-nickel alloy was produced in the same manner as in Example 1 except that platinum was replaced with ruthenium, and a rotating electrode was produced using the alloy to produce 100% carbon monoxide.
Using hydrogen containing ppm as a fuel, the change with time of the current of the rotating electrode was measured. The current obtained was substantially the same as the rotating electrode of Example 2.

[0018]

[Example 5] Platinum: cobalt = 82: 18 using a cobalt target instead of the nickel target of Example 1.
(Atomic ratio) A rotating electrode was manufactured, and the change with time of the current obtained by the rotating electrode was measured under the same conditions as in Example 1 using the rotating electrode. The result is shown in FIG. The current obtained from Fig. 2 is almost unaffected by the passage of operating time.
It can be seen that it is constant at 2.0 mA.

[0019]

Example 6 A rotating electrode was manufactured in the same manner as in Example 5 except that the atomic ratio of platinum: cobalt was set to 57:43. Using this rotating electrode, the change in current with time was measured under the same conditions as in Example 5. The result is shown in FIG. Figure 2
It can be seen that the current obtained from 1 is almost unaffected by the passage of operating time and is constant at about 1.9 mA.

[0020]

Example 7 Platinum: manganese = 80: 20 using a manganese target instead of the nickel target of Example 1.
(Atomic ratio) A rotating electrode was manufactured, and the change with time of the current obtained by the rotating electrode was measured under the same conditions as in Example 1 using the rotating electrode. The result is shown in FIG. The current obtained from Fig. 3 is almost unaffected by the passage of operating time.
It can be seen that it is constant at 1.8 mA.

[0021]

Example 8 A rotary electrode was manufactured in the same manner as in Example 7 except that the atomic ratio of platinum: manganese was set to 48:52. Using this rotating electrode, the change in current with time was measured under the same conditions as in Example 7. The result is shown in FIG. FIG.
It can be seen that the current obtained from the above is almost unaffected by the passage of operating time and is constant at about 1.8 mA.

[0022]

[Example 9] A rotating electrode of platinum: gold = 81: 19 (atomic ratio) was manufactured by using a gold target instead of the nickel target of Example 1, and the same as in Example 1 by using the rotating electrode. The change with time of the electric current obtained by the rotating electrode was measured under the conditions. The result is shown in FIG. The current obtained from Figure 4 is 3.
It is as large as 2 mA, and it can be seen that it is stable at about 2.0 mA as time passes.

[0023]

Example 10 A rotating electrode was produced in the same manner as in Example 9 except that the platinum: gold atomic ratio was set to 57:43. Using this rotating electrode, the change in current with time was measured under the same conditions as in Example 9. The result is shown in FIG. It can be seen from Fig. 4 that the current obtained is as large as 2.5 mA and is stable at 1.8 mA with the lapse of operating time.

[0024]

[Comparative Example 2] A tin target was used instead of the nickel target of Example 1 to manufacture a rotary electrode of platinum: tin = 49: 51 (atomic ratio), and the same as in Example 1 using the rotary electrode. The change with time of the electric current obtained by the rotating electrode was measured under the conditions. The result is shown in FIG. The current obtained from Fig. 5 is slightly affected by the elapsed operating time, but is 2.4-
It was stable at between 2.0 mA. Similarly, a rotating electrode of platinum: tin = 78: 22 (atomic ratio) was manufactured, and the change with time of the obtained current was measured. The result is shown in FIG. The current obtained from Fig. 5 was slightly affected by the elapsed operating time, but was stable between 2.0 and 1.6 mA.

[0025]

Comparative Example 3 Platinum: molybdenum = 6 using a molybdenum target instead of the nickel target of Example 1.
A rotating electrode with a ratio of 7:33 (atomic ratio) was manufactured, and the change with time of the current obtained by the rotating electrode was measured under the same conditions as in Example 1 using the rotating electrode. The result is shown in FIG. It can be seen from Fig. 6 that the current obtained is constant at 1.8 mA, although it is slightly affected by the elapsed operating time. Similarly, a rotating electrode of platinum: molybdenum = 45: 55 (atomic ratio) was manufactured, and the change with time of the obtained current was measured. The result is shown in FIG. It can be seen from FIG. 6 that the current obtained is smaller than that of the comparative example but is constant at 1.4 mA although it is slightly affected by the elapsed operating time.

[0026]

Comparative Example 4 A rotating electrode of platinum: germanium = 40: 60 (atomic ratio) was manufactured by using a germanium target instead of the nickel target of Example 1, and using the rotating electrode, the same as Example 1. The change with time of the electric current obtained by the rotating electrode was measured under the conditions. FIG. 7 shows the result. Figure 7
Although the current obtained from the above was slightly affected by the elapsed operating time, it was stable between 2.4 and 1.5 mA.

A rotating electrode was manufactured in the same manner as in the above Comparative Example except that the atomic ratio of platinum: germanium was 70:30. Using this rotating electrode, the change in current with time was measured under the same conditions as in Example 1. FIG. 7 shows the result. It can be seen from FIG. 7 that the current obtained was smaller than in the case of the comparative example, decreased from the initial value of 1.6 mA to 0.5 mA, and stabilized at that value. Comparing this example with each example, it can be seen that the alloy catalyst of this example can obtain a current equal to or slightly smaller than that of the tin-noble metal alloy catalyst or the molybdenum-germanium-noble metal alloy catalyst.

[0028]

INDUSTRIAL APPLICABILITY The present invention provides a polymer solid electrolyte comprising an alloy of 1 to 70 atomic% of at least one of nickel, cobalt, manganese and gold and at least one metal of platinum, palladium and ruthenium. An anode electrode catalyst for a fuel cell (Claim 1).

The anode electrocatalyst of the present invention, which is an alloy of at least one of nickel, cobalt, manganese, and gold and a noble metal, has a carbon monoxide poisoning amount as compared with a conventional platinum-only fuel cell catalyst. It is significantly reduced, and it is possible to take out a current equal to or slightly smaller than that of the tin-noble metal alloy catalyst or the germanium-molybdenum-noble metal alloy catalyst, and it is possible to continue the operation at a relatively high activity for a long period of time. . Further, even if the content of carbon monoxide in the fuel supplied to the fuel cell is relatively large, there is almost no effect on the activity, so refining of the supplied fuel is unnecessary, and the labor and cost required for refining can be reduced. You can The noble metal used is preferably platinum (claim 2), specifically nickel-
Alloy catalysts of platinum (claim 3), cobalt-platinum (claim 4), manganese-platinum (claim 5) and gold-platinum (claim 6) can be used.

[Brief description of drawings]

FIG. 1 is a graph showing changes with time of electric currents obtained with the nickel-platinum alloy catalysts of Examples 1 and 2 and the platinum plain catalyst of Comparative Example 1.

FIG. 2 is a graph showing changes with time of the electric currents obtained with the cobalt-platinum alloy catalyst and the platinum plain catalyst in Examples 5 and 6.

FIG. 3 is a graph showing changes with time of electric currents obtained with the manganese-platinum alloy catalyst and the platinum plain catalyst in Examples 7 and 8.

FIG. 4 is a graph showing changes with time of the electric currents obtained with the gold-platinum alloy catalyst and the platinum plain catalyst in Examples 9 and 10.

FIG. 5 is a graph showing changes with time of the electric currents obtained with the platinum-tin alloy catalyst and the platinum plain catalyst in Comparative Example 2.

FIG. 6 is a graph showing changes with time of the electric currents obtained with the platinum-molybdenum alloy catalyst and the platinum plain catalyst in Comparative Example 3.

FIG. 7 is a graph showing changes with time of currents obtained with a platinum-germanium alloy catalyst and a platinum plain catalyst in Comparative Example 4.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (71) Applicant 391016716 STONHART Associates Incorporated STONEHART ASSOCIATES INCORPORATED United States 06443 Connecticut, Madison, Cottage Road 17, P-O Box 1220 (72) Inventor Masanori Watanabe 8 at 2412 Wada-cho, Kofu-shi, Japan

Claims (6)

[Claims] 1. A polymer electrolyte fuel cell comprising an alloy of 1 to 70 atomic% of at least one kind of nickel, cobalt, manganese and gold and at least one kind of metal of platinum, palladium and ruthenium. Anode electrocatalyst. 2. An anode electrode catalyst for a polymer electrolyte fuel cell, comprising an alloy of platinum and 1 to 70 atomic% of at least one of nickel, cobalt, manganese and gold. 3. An anode electrode catalyst for a polymer electrolyte fuel cell, comprising an alloy of 1 to 70 atomic% of nickel and the balance of platinum. 4. An anode electrode catalyst for a polymer electrolyte fuel cell, which comprises an alloy of 1 to 70 atomic% of cobalt and the balance of platinum. 5. An anode electrode catalyst for a polymer electrolyte fuel cell, which comprises an alloy of 1 to 70 atomic% of manganese and the balance of platinum. 6. An anode electrode catalyst for a polymer electrolyte fuel cell, which comprises an alloy of 1 to 70 atomic% of gold and the balance platinum.