JP2009070691A - Fuel cell system and operation method of fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To recover characteristics of a fuel cell without accelerating deterioration of an electrolyte membrane. <P>SOLUTION: The fuel cell system is provided with a fuel cell 20 laminating one or more layer of cells which are provided a solid polymer electrolyte membrane, a fuel electrode arranged on one face of the solid polymer electrolyte membrane, an oxidant electrode arranged on the opposite face to the fuel electrode of the electrolyte membrane, and a passage plate in which passages to supply a reaction gas to the fuel electrode and the oxidant electrode are formed, a fuel gas supply device 60 to supply hydrogen-contained gas to the fuel electrode, an oxidant supply device 61 to supply an oxidant to the oxidant electrode, and a DC power source 62 which can supply current of the rated power generation time or more of the fuel cell 20 in reverse direction to the power generation time. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell system and a fuel cell operating method.

  A fuel cell is a power generation device that supplies a fuel electrode gas such as hydrogen and an oxidant electrode gas such as air, and generates an electric energy through an electrochemical reaction via an electrolyte. Since the fuel cell has low noise and the energy recovery efficiency can be higher than that of other energy engines, development as a power generation alternative generator, for example, for a factory unit or for household use is being promoted. In addition, since chemical energy is directly converted into electrical energy, NOx and SOx are not emitted, and the impact on the global environment is extremely small. Development is underway.

  In particular, since the installation space is limited for use in home use or in-vehicle use, it is desirable to make the fuel cell as small as possible. Thus, a polymer electrolyte fuel cell (PEFC) using a polymer electrolyte membrane has attracted attention because it can be operated at high power density and can be operated from room temperature.

  The PEFC cell includes a solid polymer electrolyte membrane sandwiched between a fuel electrode gas diffusion electrode and an oxidant electrode gas diffusion electrode. The fuel electrode gas diffusion electrode includes a fuel electrode catalyst layer and a fuel electrode gas diffusion layer. The oxidant electrode gas diffusion electrode includes an oxidant electrode catalyst layer and an oxidant electrode gas diffusion layer. For each of the fuel electrode gas diffusion electrode and the oxidant electrode gas diffusion electrode, a fuel electrode separator and an air electrode separator each having a gas flow path are provided on the opposite surfaces in contact with the electrolyte membrane. Further, a gasket material may be provided on the outer peripheral portion of the electrolyte membrane to prevent mixing of the fuel electrode gas and the oxidant electrode gas in the cell and leakage to the outside.

  Hydrogen or a mixed gas containing hydrogen is supplied from the outside of the cell through an inlet manifold. Moreover, it reaches the outlet manifold through the gas flow path in the separator and is discharged out of the cell. At this time, when passing through the gas flow path in the fuel electrode separator, hydrogen is dissociated into protons and electrons by a catalytic reaction at the fuel electrode gas diffusion electrode.

  The protons move in the electrolyte membrane, and the electrons generate electric power through an external circuit and move to the oxidant electrode gas diffusion electrodes, respectively. In the oxidant electrode gas diffusion electrode, water is generated by an electrochemical reaction between oxygen in the supplied gas and protons and electrons moved from the fuel electrode side, and is discharged outside from the air electrode separator.

  At this time, as protons move through the electrolyte membrane, moisture moves from the fuel electrode gas diffusion electrode to the oxidant electrode gas diffusion electrode as water accompanying the oxidant electrode gas diffusion electrode. Therefore, the oxidant electrode gas diffusion electrode becomes supersaturated by generated water and entrained water, which may inhibit the diffusion of oxygen necessary for the reaction to the oxidant gas diffusion electrode, resulting in reduced performance.

  Thus, for example, Patent Document 1 discloses a method for reducing the diffusion inhibition of the oxidant electrode gas diffusion layer by moving the moisture retained during power generation from the oxidant electrode gas diffusion layer to the fuel electrode gas diffusion layer. . In this method, an inert gas is supplied to the fuel electrode gas diffusion electrode, and a hydrogen-containing gas is supplied to the oxidant electrode gas diffusion electrode. A power source is connected to the fuel electrode gas diffusion electrode and the oxidant electrode gas diffusion electrode, and protons are moved by this power source in a direction opposite to that during power generation. Thereby, the accompanying water accompanying proton movement is forcibly moved from the oxidant electrode gas diffusion electrode to the fuel electrode gas diffusion electrode.

  Patent Document 2 discloses a method for eliminating the diffusion inhibition (flooding) of the oxidizer electrode. In this method, a current extraction plate for extracting the current obtained by power generation of the fuel cell is electrically divided into a plurality of plane directions, and protons are generated in the direction opposite to that during power generation using an external power source for the divided current extraction plate. Move. Thereby, the accompanying water accompanying proton movement is forcibly moved from the oxidant electrode gas diffusion layer to the fuel electrode gas diffusion layer.

Patent Document 3 requires an external power source that can change the direction of the current supplied to the fuel cell, thereby restoring the performance of the fuel cell by flowing current from the fuel electrode to the oxidant electrode. A method of introducing fuel from a fuel electrode to an oxidant electrode via an electrolyte membrane is disclosed.
JP 2003-272686 A JP 2005-158431 A JP 2005-166479 A

  However, in the method of Patent Document 1, if the proton moved in the direction opposite to that during power generation by the power source does not reach a predetermined value, a predetermined amount of moisture necessary for reducing the diffusion inhibition of the oxidant electrode gas diffusion layer is not obtained. Do not move. In this case, the effect of recovering the characteristics of the fuel cell cannot be obtained. Further, in the method of Patent Document 2, even when the current extraction plate is electrically divided in the plane direction and a power source is locally connected to a part of the plane to move protons in the direction opposite to that during power generation. If the amount of proton movement is less than a predetermined value, the effect of eliminating flooding cannot be obtained.

  In the method of Patent Document 3, when hydrogen is moved from the fuel electrode side to the oxidant electrode side through the electrolyte membrane by passing a current from an external power source through the flow of protons in the direction opposite to that during power generation. Consume power from the power supply. Furthermore, as an operation for restoring the performance, electric power for moving protons in the reverse direction is required. The voltage recovery operation for moving protons in the direction opposite to that during power generation will not be effective unless it continues for a predetermined time. For this reason, the recovery operation takes a long time, and the amount of power consumed for recovery also increases.

  Accordingly, an object of the present invention is to restore the characteristics of the fuel cell without accelerating the deterioration of the electrolyte membrane.

  In order to achieve the above-described object, the present invention provides a fuel cell system comprising: a solid polymer electrolyte membrane; a fuel electrode disposed on one surface of the solid polymer electrolyte membrane; and a fuel electrode of the electrolyte membrane. A fuel cell in which one or more layers of cells each including an oxidant electrode disposed on the opposite surface, and a separator having a flow path for supplying a reaction gas to the fuel electrode and the oxidant electrode are stacked; A fuel gas supply device that supplies a hydrogen-containing gas to the fuel electrode, an oxidant supply device that supplies an oxidant to the oxidant electrode, and a current that exceeds the rated power generation of the fuel cell in a direction opposite to that during power generation And means capable of doing so.

  The present invention also provides a solid polymer electrolyte membrane, a fuel electrode disposed on one surface of the solid polymer electrolyte membrane, and an oxidant electrode disposed on the surface of the electrolyte membrane opposite to the fuel electrode. And a method of operating a fuel cell in which one or more cells including a separator having a flow path for supplying a reaction gas to the fuel electrode and the oxidant electrode are stacked, and a power generation step of generating power with the fuel cell; And a recovery operation step of supplying the fuel cell with a current more than that during rated power generation in a direction opposite to the power generation step.

  According to the present invention, the characteristics of the fuel cell can be recovered without accelerating the deterioration of the electrolyte membrane.

  An embodiment of a fuel cell system according to the present invention will be described with reference to the drawings. The present invention is not limited to this embodiment.

  FIG. 2 is a cross-sectional view of the cell in the present embodiment.

  The fuel cell system of the present embodiment is a system that generates power using a solid polymer electrolyte fuel cell (PEFC). In the PEFC cell 10, a solid polymer electrolyte membrane 11 is sandwiched between a fuel electrode 12 and an oxidant electrode 13. The fuel electrode 12 includes a fuel electrode catalyst layer and a fuel electrode gas diffusion layer. The oxidant electrode 13 includes an oxidant electrode catalyst layer and an oxidant electrode gas diffusion layer. Further, a fuel electrode separator 14 and an oxidant electrode separator 15 provided with a gas flow path 22 are provided so that the fuel electrode 12 and the oxidant electrode 13 are in contact with the opposite surfaces in contact with the solid polymer electrolyte membrane 11. Yes.

  The solid polymer electrolyte membrane 11 is a cation exchange membrane such as a fluorine-based sulfonic acid resin in which a sulfone group is introduced into a fluorine-based polymer membrane. The thickness of the solid polymer electrolyte membrane 11 is, for example, about 15 to 150 μm.

  The fuel electrode 12 and the oxidant electrode 13 can be manufactured, for example, by applying a catalyst ink to a porous material that becomes a gas diffusion layer. After the fuel electrode 12 and the oxidant electrode 13 are integrated with the solid polymer electrolyte membrane 11 using a press or the like, the fuel electrode separator 14 and the oxidant electrode separator 15 are alternately stacked.

  In the stationary fuel cell system, the fuel electrode separator 14 and the air electrode separator 15 are required to have durability of tens of thousands of hours. For this reason, the fuel electrode separator 14 and the oxidant electrode separator 15 are molded by molding using, for example, a resin-carbon composite material.

  On the outer periphery of the solid polymer electrolyte membrane 11 outside the fuel electrode 12 and the oxidant electrode 13, a gasket material 21 is provided between the fuel electrode separator 14, the oxidant electrode separator 15 and the solid polymer electrolyte membrane 11. Is provided. By this gasket material 21, mixing of the fuel electrode gas and the oxidant electrode gas inside the cell 10 and leakage to the outside of the cell 10 are suppressed.

  FIG. 3 is a longitudinal sectional view of the fuel cell according to the present embodiment.

  The single electromotive voltage of the cell 10 is about 1V. Therefore, the fuel cell 20 is used by stacking a plurality of cells 10. The current collector plate 2 and the fastening plate 3 are disposed at both ends of the cell laminate 9. The cell laminate 9 is fastened by the fastening plate 3, the stud 4, the nut 5 and the disc spring 6.

  FIG. 4 shows a top view of the fuel electrode separator in the present embodiment.

  A gas flow path 22 is formed in a portion facing the fuel electrode 12 inside the fuel electrode separator 14. The fuel electrode separator 14 is formed with an inlet manifold 51 that communicates with the gas flow path 22. Hydrogen or a mixed gas containing hydrogen supplied to the inlet manifold 51 from the outside of the cell 10 flows along the gas flow path 22 formed in the fuel electrode separator 14. Hydrogen in the fuel electrode gas reaches the outlet manifold 52 while being consumed along with the electrochemical reaction, and is discharged to the outside of the fuel cell 20. The oxidant electrode separator 15 has the same structure as the fuel electrode separator 14. The air supplied to the oxidant electrode separator 15 via the manifold reaches the outlet manifold while being consumed with the electrochemical reaction, and is discharged to the outside of the fuel cell 20.

  FIG. 1 is a block diagram of a fuel cell system in the present embodiment.

  The fuel cell system includes a fuel cell 20, a fuel gas supply device 60, and an oxidant supply device 61. The fuel gas supply device 60 supplies fuel gas to the fuel cell 20. The oxidant supply device 61 supplies oxidant gas to the fuel cell 20.

  The fuel gas supply device 60 includes a reformer that reforms, for example, natural gas, LPG, or kerosene into a hydrogen-rich gas using raw fuel, and supplies the reformed gas to the fuel cell 20 as a fuel electrode gas. To do. The fuel gas supply device 60 may supply hydrogen gas directly to the fuel cell 20 using a hydrogen cylinder or the like without having a reformer. The oxidant supply device 61 supplies air, for example, as an oxidant gas using an air blower, an air compressor, or the like.

  The fuel gas supply device 60 is connected to an inlet manifold 51 that communicates with the gas flow path 22 formed in the fuel electrode separator 14 via a fuel supply valve 71. The oxidant supply device 61 is connected to an inlet manifold that communicates with the gas flow path 22 formed in the oxidant electrode separator 15 via an oxidant supply valve 72. The fuel gas supply device 60 is also connected to an inlet manifold that communicates with the gas flow path 22 formed in the oxidant electrode separator 15 via the oxidant electrode fuel supply valve 75. An outlet valve 74 is connected to an outlet manifold that communicates with the gas flow path 22 formed in the oxidant electrode separator 15.

  Further, the fuel cell system has a DC power source 62 connected to the fuel cell 20. The direct current power source 62 is a device that supplies direct current to the fuel cell 20. As the DC power source 62, for example, an external power supply device, a power source capable of charging / discharging such as a storage battery, a secondary battery, and a capacitor may be used. Further, when the fuel cell system is connected to the grid power system, a device that converts the grid power to DC by an inverter and supplies a DC current to the fuel cell 20 may be used as the DC power supply 62.

  The fuel cell system may further include a voltage measuring device 81 that monitors the voltage during power generation of the fuel cell 20. The voltage measuring device 81 is connected to the control device 82. The control device 82 is connected to the fuel supply valve 71, the oxidant supply valve 72, and the like, and can control the operation of the fuel cell system.

  In a normal operation state in which the fuel cell system supplies power to the outside, for example, the control device 82 opens the fuel supply valve 71 and the oxidant supply valve 72 and closes the oxidant electrode fuel supply valve 75. In this state, hydrogen gas or hydrogen-containing gas is supplied from the fuel gas supply device 60 to the inlet manifold of the fuel electrode of the fuel cell 20. Further, air is supplied as an oxidant from the oxidant supply device 61 to the inlet manifold of the oxidant electrode 13.

  The reaction gas supplied to the inlet manifold is supplied to the fuel electrode separator 14 and the oxidant electrode separator 15, respectively. Hydrogen supplied to the fuel electrode 12 is dissociated into protons and electrons by a catalytic reaction. The protons move through the solid polymer electrolyte membrane 11, and the electrons pass through an external circuit to generate electric power and move to the oxidant electrode 13.

  In the oxidant electrode 13, water is generated by an electrochemical reaction between oxygen in the supplied gas, protons and electrons moved from the fuel electrode 12 side, and is formed outside the fuel cell 20 via the oxidant electrode separator 15. Discharged. At this time, as protons move through the solid polymer electrolyte membrane 11, moisture moves from the fuel electrode 12 to the oxidant electrode 13 as entrained water through the solid polymer electrolyte membrane 11 to the oxidant electrode 13. Therefore, the oxidant electrode 13 becomes supersaturated by the generated water and the accompanying water, and moisture accumulates in the oxidant electrode 13 with the power generation time. For this reason, diffusion of oxygen necessary for the reaction to the oxidant electrode 13 is inhibited, and the voltage of the fuel cell 20 is lowered.

  When the voltage at the time of power generation of the fuel cell 20 measured by the voltage measuring device 81 becomes equal to or lower than a predetermined voltage, the fuel supply valve 71 and the oxidant supply valve 72 are closed by the control device 82, for example, and the fuel cell Power generation by 20 is stopped. Further, the oxidant electrode fuel supply valve 75 is opened, and hydrogen gas or a hydrogen mixed gas is supplied to the oxidant electrode 13. In this state, a recovery operation for supplying electric power from the DC power source 62 is performed so that a current flows from the fuel electrode 12 to the oxidant electrode 13.

  In normal operation of the fuel cell 20, air is supplied to the oxidizer electrode 13. For this reason, if hydrogen or a hydrogen mixed gas is supplied to the oxidant electrode 13 immediately after the power generation of the fuel cell 20 is stopped, it reacts with the remaining oxygen in the air and becomes high temperature, causing deterioration of the solid polymer electrolyte membrane 11. There is a risk of acceleration. Therefore, a means for purging the oxygen-containing gas staying in the oxidant electrode 13 using nitrogen or natural gas is provided, and after purging, hydrogen or a hydrogen mixed gas is introduced into the oxidant electrode 13. Good.

  Alternatively, after stopping the power supply to the outside, at least the oxidant supply valve 72 and the outlet valve 74 attached to the outlet and the inlet of the oxidant electrode 13 are closed. As a result, the hydrogen staying in the fuel electrode permeates the oxidant electrode through the solid polymer electrolyte membrane 11 by concentration diffusion and reacts with the oxygen in the oxidant electrode 13 to consume oxygen. The oxygen concentration of the water decreases.

  The decrease in oxygen concentration in the oxidant electrode 13 caused by purging or closing the valve on the inlet side and the outlet side of the oxidant electrode 13 causes the voltage of the fuel cell 20 measured by the voltage measuring device 81 to be a predetermined value, for example, 100 mV / cell or less. Can be determined. Alternatively, the purge amount is determined from the volume of the oxidant gas during operation, and hydrogen is introduced into the oxidant electrode 13 after purging a predetermined amount, thereby suppressing the reaction between the remaining oxygen and the supplied hydrogen. it can.

  FIG. 5 is a graph showing the characteristic voltage recovery rate when the recovery operation is performed on the fuel cell in the present embodiment. The vertical axis indicates the rate of voltage increase of the fuel cell 20 before and after the recovery operation. This figure also shows the case where the current supplied from the external DC power supply 62 is equivalent to the rated load of the fuel cell 20, equivalent to 1.5 times the rated load, and equivalent to twice the rated load. Yes.

  When the supply current value from the external DC power supply 62 during the recovery operation is equivalent to the rated power generation of the fuel cell system, the voltage of the fuel cell 20 is hardly recovered. On the other hand, the characteristic of the fuel cell 20 is restored by flowing a current larger than that in the case of rated power generation from the fuel electrode 12 to the oxidant electrode 13 via the DC power supply 62.

  This is because in normal power generation operation, water is generated along with the electrochemical reaction of hydrogen and oxygen together with proton-entrained water in the oxidizer electrode 13, whereas in the recovery operation, protons are generated. This is because only the water accompanying the movement moves from the oxidant electrode 13 to the fuel electrode 12. That is, in order to move the moisture remaining in the oxidant electrode 13 during the power generation of the fuel cell 20 to the fuel electrode 12, the current during the recovery operation is set to a current higher than the rated power generation of the fuel cell 20, and the oxidant electrode 13 There is a need to remove a wider range of accumulated water causing diffusion inhibition.

  The fuel electrode 12 and the oxidant electrode 13 are electrically insulated by the solid polymer electrolyte membrane 11, but the solid polymer electrolyte membrane 11 allows moisture to permeate due to the concentration difference. In order to move the moisture remaining in the oxidant electrode 13 to the fuel electrode 12 by the recovery operation, it is necessary to increase the current during the recovery operation and increase the moving speed of the moisture from the oxidant electrode 13 to the fuel electrode 12.

  FIG. 6 is a graph showing the change over time of the voltage increase rate when the recovery operation is performed on the fuel cell in the present embodiment. The horizontal axis represents the DC current application operation time, and the vertical axis represents the voltage between the fuel electrode 12 and the oxidant electrode 13 when the DC current is applied. This figure shows the results when the supply current from the external DC power supply 62 is increased in order, corresponding to the rated load of the fuel cell 20, equivalent to 1.5 times the rated load, and equivalent to twice the rated load. Show.

  The lower the voltage between the fuel electrode 12 and the oxidant electrode 13, the more efficiently protons are generated, transferred, and reduced to hydrogen. Therefore, it is desirable that the voltage between the fuel electrode 12 and the oxidant electrode 13 be reduced during the recovery operation.

  As is clear from FIG. 6, the voltage between the fuel electrode 12 and the oxidant electrode 13 is hardly changed at the current corresponding to the rated load, but is equivalent to 1.5 times the rated load or twice the rated load. It can be seen that by applying a considerable current, the voltage between the fuel electrode 12 and the oxidant electrode 13 is reduced during the recovery operation, and the effect of the recovery operation is obtained. Therefore, in order to recover the flooding of the oxidizer electrode 13, it is necessary to flow a current value equal to or higher than the rated power generation of the fuel cell 20.

  FIG. 7 is a graph showing changes in platinum surface area with respect to the recovery operation duration in the present embodiment. The vertical axis represents the ratio to the platinum surface area before continuous power generation operation. This figure also shows the case where the recovery operation is performed after the fuel cell 20 has been continuously operated for 700 hours, 2700 hours, and 3000 hours.

  Platinum is an effective catalyst for the electrochemical reaction at the oxidant electrode 13. It can be seen that the surface area effective for electrochemical reaction is reduced by flooding, whereas the surface area is recovered by the recovery operation. In particular, a remarkable recovery of the platinum surface area is observed by continuing the recovery operation for 3 hours or more. Therefore, it is effective that the effect of the recovery operation is continuously performed for a predetermined time, particularly 3 hours or more.

  As described above, in the present embodiment, a current in the direction opposite to that during power generation is supplied to the fuel cell 20 to move a proton amount larger than the rated load of the fuel cell 20 from the oxidant electrode 13 to the fuel electrode 12. As a result, the water remaining in the oxidant electrode 13 during the power generation of the fuel cell 20 can be forcibly moved from the oxidant electrode 13 to the fuel electrode 12 as water accompanying protons. For this reason, the moisture staying in the oxidant electrode 13 and hindering the diffusion of the reaction gas is reduced, and oxygen as the oxidant is easily diffused into the electrode catalyst.

  Further, there are cases where impurities that hinder the electrochemical reaction or proton movement are present on the solid polymer electrolyte membrane 11 or the catalyst surface. However, by supplying current from the DC power supply 62 to the fuel cell 20 as in the present embodiment, impurities are also carried out of the cell 10, so that the voltage of the fuel cell 20 is improved.

  Furthermore, after reducing the concentration of oxygen remaining in the oxidant electrode 13, hydrogen necessary for operation is introduced into the oxidant electrode 13, so that hydrogen does not react with oxygen at the oxidant electrode 13, and the electrolyte membrane 11. Acceleration of deterioration can be suppressed. For this reason, the characteristics of the fuel cell 20 can be recovered.

  Thus, in the fuel cell system in the present embodiment, the characteristics of the fuel cell can be recovered without accelerating the deterioration of the electrolyte membrane.

It is a block diagram in one embodiment of a fuel cell system concerning the present invention. It is sectional drawing of the cell in one Embodiment of the fuel cell system which concerns on this invention. 1 is a longitudinal sectional view of a fuel cell in one embodiment of a fuel cell system according to the present invention. The top view of the fuel electrode separator in one embodiment of the fuel cell system concerning the present invention is shown. It is a graph which shows the characteristic voltage recovery rate at the time of performing recovery operation to the fuel cell in one embodiment of the fuel cell system concerning the present invention. It is a graph which shows the time change of the voltage increase rate at the time of performing recovery operation to the fuel cell in one embodiment of the fuel cell system concerning the present invention. It is a graph which shows the change of the platinum surface area with respect to recovery operation continuation time in one embodiment of the fuel cell system concerning the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 ... Fastening plate, 4 ... Stud, 5 ... Nut, 6 ... Belleville spring, 9 ... Cell laminated body, 10 ... Cell, 11 ... Solid polymer electrolyte membrane, 12 ... Fuel electrode, 13 ... Oxidizer electrode, 14 ... Fuel electrode separator, 15 ... oxidant electrode separator, 20 ... fuel cell, 21 ... gasket material, 22 ... gas flow path, 51 ... inlet manifold, 52 ... outlet manifold, 60 ... fuel gas supply device, 61 ... oxidant supply device 62 ... DC power supply, 71 ... Fuel supply valve, 72 ... Oxidant supply valve, 74 ... Outlet valve, 75 ... Oxidizer electrode fuel supply valve, 81 ... Voltage measuring device, 82 ... Control device

Claims (7)

A solid polymer electrolyte membrane; a fuel electrode disposed on one surface of the solid polymer electrolyte membrane; an oxidant electrode disposed on a surface opposite to the fuel electrode of the solid polymer electrolyte membrane; A fuel cell in which one or more layers of cells each including a fuel electrode and a separator in which a flow path for supplying a reaction gas to the oxidant electrode is formed;
A fuel gas supply device for supplying a hydrogen-containing gas to the fuel electrode;
An oxidant supply device for supplying an oxidant to the oxidant electrode;
Means capable of supplying a current greater than or equal to the rated power generation of the fuel cell in a direction opposite to that during power generation;
A fuel cell system comprising:   2. The fuel cell system according to claim 1, further comprising means for purging oxygen-containing gas that has accumulated in the oxidant electrode after power generation by the fuel cell.   The fuel cell system according to claim 1, further comprising an oxidant electrode fuel supply unit configured to supply the hydrogen-containing gas to the oxidant electrode. A voltage measuring device for measuring the voltage of the fuel cell;
A control device for operating the oxidant electrode fuel supply means when the voltage measured by the voltage measuring device is less than or equal to a predetermined value per cell;
The fuel cell system according to claim 3, further comprising: A solid polymer electrolyte membrane, a fuel electrode disposed on one surface of the solid polymer electrolyte membrane, an oxidant electrode disposed on a surface of the electrolyte membrane opposite to the fuel electrode, the fuel electrode, and In a method for operating a fuel cell in which one or more cells including a separator having a flow path for supplying a reaction gas to the oxidant electrode are stacked,
A power generation step of generating power with the fuel cell;
A recovery operation step of supplying a current equal to or higher than the rated power generation to the fuel cell in a direction opposite to the power generation step;
A method for operating a fuel cell, comprising:   6. The method of operating a fuel cell according to claim 5, further comprising a step of supplying a hydrogen-containing gas to the oxidant electrode after the power generation step and before the recovery operation step.   The method for operating a fuel cell according to any one of claims 5 and 6, wherein the recovery operation step is performed continuously for a predetermined time.

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