JP2006202643A - Fuel cell system and control method of fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance 4-electron reduction performance of oxygen in a fuel cell system and enhance durability of an MEA. <P>SOLUTION: A fuel cell system has (A) a fuel cell circuit constituted with a cell using a platinum catalyst and/or a platinum alloy system catalyst as an electrode catalyst and (B) a fuel cell circuit constituted with a cell using a chalcogenide-based catalyst as the electrode catalyst arranged in parallel. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell system that can be expected to generate electric power efficiently and constantly, and a control method for the fuel cell system.

  Platinum or a platinum alloy-based catalyst is used as the anode catalyst of the polymer electrolyte fuel cell. Specifically, a catalyst in which a noble metal including platinum is supported on carbon black has been used. Platinum-supported carbon black is obtained by adding sodium hydrogen sulfite to a chloroplatinic acid aqueous solution, reacting with hydrogen peroxide solution, adsorbing the resulting platinum colloid to carbon black, washing, and heat-treating as necessary. The preparation method is general. In a polymer electrolyte fuel cell, platinum-supported carbon black is dispersed in a polymer electrolyte solution to form a paste. The paste is applied to a gas diffusion electrode such as carbon paper, dried, and then dried with two gas diffusion electrodes. An electrolyte membrane-electrode assembly (MEA) is manufactured by sandwiching a molecular electrolyte membrane and performing hot pressing.

On the other hand, it is known that when oxygen (O ₂ ) is electrolytically reduced, superoxide is generated by one-electron reduction, hydrogen peroxide is generated by two-electron reduction, and water is generated by four-electron reduction. In a fuel cell stack using platinum or a platinum-based catalyst as an electrode, if a voltage drop occurs for some reason, the 4-electron reducibility is reduced and the 2-electron reducibility is obtained. For this reason, hydrogen peroxide is generated, which causes deterioration of MEA.

  Recently, a low-cost fuel cell catalyst that does not require an expensive platinum catalyst has been developed by a reaction in which oxygen is reduced by four electrons to generate water. Non-Patent Document 1 below discloses that a catalyst having a chalcogen element is excellent in 4-electron reducibility and suggests application to a fuel cell.

  Patent Document 1 below discloses a two-electron reduction reaction that produces hydrogen peroxide by electrochemical reduction of oxygen for the purpose of apparently increasing the four-electron reduction reaction relative to the electrochemical reduction of oxygen. The oxygen reduction composite electrode is configured to contain an electrochemical catalyst A that catalyzes and a catalyst B that catalyzes a decomposition reaction that decomposes the generated hydrogen peroxide to generate oxygen. Using the electrode potential of the composite electrode for oxygen reduction as the oxygen reduction potential of the electrochemical catalyst A, the oxygen regenerated by decomposing hydrogen peroxide by the catalyst B is reduced by the electrochemical catalyst A by two electrons, and the hydrogen peroxide is reduced. It is disclosed to generate repeatedly.

JP 2003-151567 A Electrochimica Acta 45 (2000) 4237-4250

  Platinum and platinum alloy-based catalysts undergo 4-electron reduction mainly under normal operating conditions, and produce water from hydrogen and oxygen. However, when the voltage drops for some reason during operation, the rate of two-electron reduction increases, and hydrogen peroxide is generated from hydrogen and oxygen, which causes the MEA to deteriorate. In order to prevent an increase in the degradation of the MEA, the system is stopped when it falls below a certain voltage value. Thus, platinum and platinum alloy-based catalysts have been extremely difficult to control as fuel cell operating systems.

  On the other hand, the fuel cell using the chalcogenide catalyst described in Non-Patent Document 1 is inferior in terms of output in normal operation. The catalyst described in Patent Document 1 is intended to improve the 4-electron reduction reaction, and is not intended to be used in combination with conventional platinum or platinum alloy catalysts.

  An object of the present invention is to improve the 4-electron reduction performance of oxygen in a fuel cell system and improve the durability of MEA.

  The present inventor has found that the above problem can be solved by using a conventional platinum or platinum alloy catalyst and a chalcogenide catalyst together, and has reached the present invention.

  That is, first, the present invention is an invention of a fuel cell system, (A) a fuel cell circuit constituted by cells using platinum and / or a platinum alloy-based catalyst as an electrode catalyst, and (B) an electrode catalyst. And a fuel cell circuit constituted by cells using a chalcogenide catalyst as described above.

  In the fuel cell system of the present invention, (A) a fuel cell circuit constituted by a cell using platinum and / or a platinum alloy catalyst as the electrode catalyst, and (B) a cell using a chalcogenide catalyst as the electrode catalyst. It is preferable to have a switch for switching the fuel cell circuit constituted by

  Although it is inferior in terms of output, stacking a cell using a chalcogenide-based catalyst while the voltage drop is small by simultaneously arranging cells using a chalcogenide-based catalyst that has higher 4-electron reducing properties than platinum or platinum alloy-based catalysts. To switch to. Thereby, generation | occurrence | production of a hydrogen peroxide can be suppressed and the effect which can hold | maintain a driving | running | working possible state can be anticipated, suppressing deterioration of MEA. According to the present invention, the voltage value at which the system is stopped can be set to a lower limit value, and the rate at which the system is stopped can be reduced. The number of reaction electrons in a fuel cell using platinum and / or a platinum alloy catalyst is about 3.7, whereas the number of reaction electrons in a fuel cell using a chalcogenide catalyst is about 4.0. .

  In the present invention, in the fuel cell system, (A) a fuel cell circuit constituted by cells using platinum and / or a platinum alloy catalyst as the electrode catalyst, and (B) a chalcogenide catalyst as the electrode catalyst. It is preferable to have at least one voltage monitoring monitor for monitoring the electromotive force of the fuel cell circuit constituted by the used cells in the system and the circuits (A) and (B). For example, a voltage monitoring monitor is arranged at a rate of one cell per several cells. The voltage value of these voltage monitoring monitors is monitored, and when the voltage falls below a certain value, the cell stack side circuit using the platinum and / or platinum alloy catalyst is shut off, and the cell stack using the chalcogenide catalyst A circuit that allows voltage to flow only to the side.

The chalcogenide catalyst referred to in the present invention is a general formula A _x B _y C _z (A: one or more elements selected from Mo, W, Re, B: one or more selected from Ru, Os, Rh) Element represented by C: S, Se, or Te), and is disclosed in Non-Patent Document 1, for example. More specifically _{include Mo 2 Ru 2 S 5, W} 2 Ru 2 S 5, Re 2 Ru 2 S 5, Mo 2 Os 2 S 5, Mo 2 Rh 2 S 5.

  In the present invention, it is also preferable to provide a normal secondary battery as an auxiliary circuit of a cell using a chalcogenide catalyst as the electrode catalyst (B) in order to control the fuel cell system more smoothly.

  By the way, in a fuel cell stack system in which a cell using a Pt and / or Pt alloy system and a cell using a chalcogenide catalyst are arranged in parallel as an electrode catalyst, one cell is stopped (OCV state), and the rest When only the cell is operated, the MEA may be deteriorated on the cell side in the stopped state. At the same time, it leads to a reduction in fuel consumption. In a fuel cell stack system in which a cell using a Pt and / or Pt alloy system and a cell using a chalcogenide catalyst are arranged in parallel as an electrode catalyst, when only one cell is stopped, the anode intake system is If it is common, it is because hydrogen also flows into the stopped cell side. That is, it is known that in the stopped (OCV) state, hydrogen on the anode side permeates to the cathode side and degrades the MEA. In addition, in a stopped state, hydrogen that does not participate in power generation passes through the cell, so that fuel efficiency is deteriorated.

  Therefore, in the present invention, (A) a fuel cell circuit constituted by a cell using platinum and / or a platinum alloy catalyst as an electrode catalyst, and (B) constituted by a cell using a chalcogenide catalyst as an electrode catalyst. It is preferable to provide an openable / closable valve on the anode intake side of the fuel cell circuit. Specifically, a control valve attached to a shaft that is rotated by a motor is installed in the middle of the anode intake line. This valve is rotated by a shaft that is rotated by a motor to open and close the intake line. This motor is controlled by the ECU and rotates in accordance with the operation / stop state of each cell. As a result, the anode intake line is opened and closed depending on the operating state.

  By closing the valve on the cell in the stopped state, hydrogen is not supplied to the cell in the stopped (OCV) state. Therefore, (1) reducing the amount of hydrogen that permeates to the cathode side prevents deterioration of MEA and improves durability, and (2) improves fuel efficiency by not supplying hydrogen to cells that do not generate electricity. be able to.

  2ndly, this invention is invention of the control method of a fuel cell system, (A) The fuel cell circuit comprised by the cell using platinum and / or a platinum alloy type catalyst as an electrode catalyst, (B) Electrode A control method of a fuel cell system in which a fuel cell circuit configured by a cell using a chalcogenide catalyst as a catalyst is arranged in parallel, depending on the electromotive force of the circuits (A) and (B). The output is switched to one of them. By simultaneously arranging cells using a chalcogenide-based catalyst that has a higher 4-electron reductivity than platinum or platinum alloy-based catalysts, switching to stack running using a chalcogenide-based catalyst while the voltage drop is small, the MEA's Suppress deterioration.

  Specifically, when the output of the fuel cell system falls below a predetermined value, the circuit (A) is shut off and only the circuit (B) is output.

  Thirdly, the present invention is a fuel cell vehicle equipped with the above fuel cell system, which improves stable running and durability.

  Although it is inferior in terms of output, stacking a cell using a chalcogenide-based catalyst while the voltage drop is small by simultaneously arranging cells using a chalcogenide-based catalyst that has higher 4-electron reduction than platinum or platinum alloy-based catalysts. To switch to. Thereby, generation | occurrence | production of a hydrogen peroxide can be suppressed and the effect which can hold | maintain a driving | running | working possible state can be anticipated, suppressing deterioration of MEA. In the current fuel cell system, when the voltage drop detected from the voltage monitor installed in each cell or every several cells for the purpose of suppressing the remarkable generation of hydrogen peroxide and avoiding the deterioration of MEA exceeds a certain value, Stop the system. According to the present invention, the voltage drop width can be set to a lower limit value, and the rate of system stop can be reduced.

  FIG. 1 schematically shows the arrangement of fuel cells and the like in the fuel cell system of the present invention. A fuel cell circuit 2 constituted by a single cell 1 using platinum and / or a platinum alloy catalyst as an electrode catalyst and a fuel cell circuit 4 constituted by a single cell 3 using a chalcogenide catalyst as an electrode catalyst are arranged in parallel. Is arranged. In these circuits, a predetermined number of voltage monitoring monitors 5 are arranged to monitor the power generation status of the single cell 1 and the fuel cell circuit 2 and the power generation status of the single cell 3 and the fuel cell circuit 4. The fuel cell circuit 2 and the fuel cell circuit 4 are appropriately switched by a circuit changeover switch 6.

  FIG. 1A shows the state of the circuit selector switch 6 during normal operation. Electric power generated from a fuel cell circuit 2 constituted by a single cell 1 using platinum and / or a platinum alloy-based catalyst is supplied to the outside. FIG. 1B shows the state of the circuit changeover switch 6 when the voltage of the fuel cell circuit 2 constituted by the single cell 1 using platinum and / or a platinum alloy-based catalyst is lowered for some reason during operation. Show. Hydrogen peroxide in the single cell 1 using platinum and / or a platinum alloy catalyst by switching to power generation of the fuel cell circuit 4 constituted by the single cell 3 using the chalcogenide catalyst while the voltage drop width is small. Generation | occurrence | production can be suppressed and a driving | running | working possible state can be hold | maintained, suppressing deterioration of MEA. When the voltage of the fuel cell circuit 2 constituted by the single cell 1 using platinum and / or a platinum alloy-based catalyst is restored, the circuit change-over switch 6 is switched again to use a normal platinum and / or platinum alloy-based catalyst. The operation is performed by the fuel cell circuit 2 configured by the single cell 1.

  In FIG. 2, (A) an anode intake line 7 from the fuel cell circuit 2 constituted by a cell using platinum and / or a platinum alloy catalyst as an electrode catalyst, and (B) a chalcogenide catalyst as an electrode catalyst. The fuel cell stack layout diagram in the case where the openable and closable valves 10 and 11 are provided in a portion (control valve installation region 12) where the anode intake line 8 from the fuel cell circuit 4 constituted by cells is parallel is shown. The anode intake lines 7 and 8 merge after passing through the control valve installation region 12 to form one intake line 9. The control valves 10 and 11 attached to the shaft rotated by the motor 13 are rotated by the shaft rotated by the motor 13 to open and close the intake line.

  FIG. 3 shows the correspondence between the anode intake lines 7 and 8 and the valves 10 and 11. In FIG. 3A, (A) a fuel cell circuit 2 constituted by a cell using platinum and / or a platinum alloy catalyst as an electrode catalyst is operated, and (B) a cell using a chalcogenide catalyst as an electrode catalyst. The valve 10 on the anode intake line 7 side is opened, and the valve 11 on the anode intake line 8 side is closed. FIG. 3B is the opposite, (A) the fuel cell circuit 2 constituted by a cell using platinum and / or a platinum alloy catalyst as an electrode catalyst is stopped, and (B) a chalcogenide catalyst as an electrode catalyst. This shows a case where the fuel cell circuit 4 constituted by the cells using is operated, the valve 10 on the anode intake line 7 side is closed, and the valve 11 on the anode intake line 8 side is opened. The motor 13 is controlled by the ECU and rotates according to the operation / stop state of each cell. As a result, the anode intake line is opened and closed depending on the operating state.

[Measurement of number of reaction electrons]
Using Ru ₄ MoS ₅ / C as the chalcogenide (S-based) catalyst, the redox current value I for the set angular velocity ω was measured, and ω ^−1/2 and 1 / ID (D: electrode area (cm ² )) The relationship is illustrated. The number of reaction electrons of 3.78 was determined from the slope of the straight line 5.76 shown in FIG. Further, Ru5MoS15 / C was used as a chalcogenide (S-based) catalyst, I was measured for the set angular velocity ω, and the relationship between ω ^−1/2 and 1 / ID was illustrated. The number of reaction electrons 3.83 was determined from the slope of the straight line 5.68 shown in FIG.

Similarly, using Ru ₅ MoSe ₅ / C as the chalcogenide (Se-based) catalyst, the oxidation-reduction current value I with respect to the set angular velocity ω was measured, and the relationship between ω ^−1/2 and 1 / ID was illustrated. The number of reaction electrons of 3.93 was determined from the slope of the straight line shown in FIG.

For comparison, an oxidation-reduction current value I with respect to the set angular velocity ω was measured using a platinum catalyst, and the relationship between ω ^−1/2 and 1 / ID was illustrated. The number of reaction electrons of 3.63 was determined from the slope of the straight line shown in FIG.

  Accordingly, it can be seen that the chalcogenide catalyst used in the present invention has a higher 4-electron reducing property than the platinum catalyst.

  By mounting the fuel cell system of the present invention on a fuel cell vehicle or the like, stable running and durability are improved. This contributes to the spread of fuel cells.

FIG. 2 is a layout view of fuel cells and the like in the fuel cell system of the present invention. A fuel cell stack layout diagram in the case where the openable and closable valves 10 and 11 are provided in the portion where the anode intake lines 7 and 8 are parallel (control valve installation region 12) is shown. The correspondence between the anode intake lines 7 and 8 and the valves 10 and 11 is shown. The relationship graph of (omega) ^-1/2 and 1 / ID for measuring the number of reaction electrons.

Explanation of symbols

1: a single cell using platinum and / or a platinum alloy catalyst as an electrode catalyst, 2: a fuel cell circuit constituted by the single cell 1, 3: a single cell using a chalcogenide catalyst as an electrode catalyst, 4: a single cell 5: voltage monitoring monitor, 6: circuit changeover switch, 7: anode intake line from fuel cell circuit 2, 8: anode intake line from fuel cell circuit 4, 9: intake line 7 , 8 merged, 10: valve, 11: valve, 12: control valve installation area, 13: motor.

Claims (12)

  (A) A fuel cell circuit constituted by a cell using platinum and / or a platinum alloy catalyst as an electrode catalyst and (B) a fuel cell circuit constituted by a cell using a chalcogenide catalyst as an electrode catalyst are arranged in parallel. A fuel cell system, wherein   In the fuel cell system, (A) a fuel cell circuit constituted by a cell using platinum and / or a platinum alloy catalyst as an electrode catalyst, and (B) a cell using a chalcogenide catalyst as an electrode catalyst. The fuel cell system according to claim 1, further comprising a switch that switches a configured fuel cell circuit as needed.   In the fuel cell system, (A) a fuel cell circuit constituted by a cell using platinum and / or a platinum alloy catalyst as an electrode catalyst, and (B) a cell using a chalcogenide catalyst as an electrode catalyst. 3. The fuel cell according to claim 1, wherein the system and the circuits (A) and (B) have at least one voltage monitoring monitor for monitoring an electromotive force of the fuel cell circuit configured. 4. system. The chalcogenide-based catalyst is represented by the general formula A _x B _y C _z (A: one or more elements selected from Mo, W, Re, B: one or more elements selected from Ru, Os, Rh, C 4. The fuel cell system according to claim 1, wherein the fuel cell system is represented by: one or more elements selected from S, Se, and Te.   5. The fuel cell system according to claim 1, further comprising a secondary battery as an auxiliary circuit of a cell using a chalcogenide catalyst as the electrode catalyst.   (A) a fuel cell circuit constituted by a cell using platinum and / or a platinum alloy catalyst as an electrode catalyst, and (B) a fuel cell circuit constituted by a cell using a chalcogenide catalyst as an electrode catalyst. 6. The fuel cell system according to claim 1, wherein a valve that can be opened and closed is provided on the anode intake side.   (A) A fuel cell circuit constituted by a cell using platinum and / or a platinum alloy catalyst as an electrode catalyst and (B) a fuel cell circuit constituted by a cell using a chalcogenide catalyst as an electrode catalyst are arranged in parallel. A method for controlling a fuel cell system, wherein the output is switched to either one of the circuits (A) and (B) at any time according to the electromotive force of the circuits (A) and (B).   8. The method of controlling a fuel cell system according to claim 7, wherein when the output of the fuel cell system falls below a predetermined value, the circuit (A) is shut off and only the circuit (B) is output. The chalcogenide-based catalyst is represented by the general formula A _x B _y C _z (A: one or more elements selected from Mo, W, Re, B: one or more elements selected from Ru, Os, Rh, C The method for controlling a fuel cell system according to claim 7 or 8, wherein the control method is represented by: one or more elements selected from S, Se, and Te.   10. The fuel cell system control method according to claim 7, further comprising a secondary battery as an auxiliary circuit of a cell using a chalcogenide catalyst as the electrode catalyst (B).   (A) a fuel cell circuit constituted by a cell using platinum and / or a platinum alloy catalyst as an electrode catalyst, and (B) a fuel cell circuit constituted by a cell using a chalcogenide catalyst as an electrode catalyst. A control method for a fuel cell system in which a valve that can be freely opened and closed is provided on the anode intake side, and the valve on the anode intake side of the fuel cell circuit in which the cell is stopped is closed during a cell operation state in which the output is switched to one of them. The method for controlling a fuel cell system according to any one of claims 7 to 10.   A fuel cell vehicle equipped with the fuel cell system according to any one of claims 1 to 6.

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