JP2009123534A - Performance recovery method of solid polymer fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize recovery of fuel cell performance safely, simply and certainly without carrying out fuel introduction into an oxidant electrode and various severe controls. <P>SOLUTION: Operation of fuel cell of a solid polymer fuel cell FC is shut down and pure water is supplied to the fuel cell FC from piping 4 to a passage on current collector 26 side which becomes an oxidant electrode at the operation of the fuel cell. Electric power is supplied to the current collectors 25, 26 so as to flow current from the outside power source 15 in reverse direction from the operation time of the fuel cell, and the pure water is electrolyzed, thereby, the performance of the fuel cell FC is recovered. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for recovering the performance of a polymer electrolyte fuel cell.

  In polymer electrolyte fuel cells, impurities contained in supply gas and humidified water and inorganic and organic components eluted from each base material constituting the battery system accumulate in the battery as pollutants during long-term operation. . As a result, the reaction field decreases, and the performance of the battery decreases.

  More specifically, the internal resistance (overvoltage) that lowers the performance of the polymer electrolyte fuel cell includes a resistance overvoltage, an activation overvoltage, and a diffusion overvoltage. Due to the accumulation of the pollutants and the decrease in gas diffusibility associated with the wetting of the base material, these overvoltages gradually increase and the performance of the fuel cell deteriorates.

  As a technique for recovering the performance degradation of such a polymer electrolyte fuel cell, the fuel is supplied to the oxidant electrode side during the fuel cell operation directly or via the membrane electrode assembly, and then the original fuel cell operation is performed. To restore the fuel cell performance by operating the fuel cell so that the current flows in the opposite direction, or by introducing the fuel to the fuel electrode side and flowing the current from the external power source from the oxidizer electrode to the fuel electrode Has been proposed (Patent Documents 1 to 3).

JP 2001-85037 A JP 2003-272686 A JP 2005-166479 A

  However, when the electrode catalyst is brought into contact with hydrogen as a fuel and oxygen as an oxidant, a vigorous reaction occurs on the catalyst. This not only reduces power generation efficiency, but also damages the membrane depending on the concentration of hydrogen and oxygen, which can lead to damage to the battery because it loses the seal between the fuel electrode and oxidant electrode that should be fulfilled. There is. For this reason, it is necessary to completely eliminate the possibility of mixing fuel and oxidant. Further, in the methods of Patent Documents 1 and 2, it is necessary to strictly monitor a plurality of parameters such as a current value applied to the fuel cell from the outside and a hydrogen flow rate to be supplied, and the control becomes complicated. There was a problem.

  The present invention has been made in view of the above points, and an object of the present invention is to safely, easily, and reliably recover the fuel cell performance without introducing fuel into the oxidizer electrode and performing various strict controls. It is said.

  In order to achieve the above object, the present invention provides pure water to the oxidant electrode side during operation of a fuel cell in a polymer electrolyte fuel cell, and to the current collector of the polymer electrolyte fuel cell. On the other hand, the performance of the polymer electrolyte fuel cell is restored by performing the water electrolysis operation that electrolyzes the pure water by supplying power from the external power supply so that the current in the direction opposite to that in the fuel cell operation flows. It is characterized by letting.

In the present invention, the water electrolysis operation is performed by supplying pure water to the oxidant electrode side during fuel cell operation and applying electricity from the outside. At this time, a chemical reaction represented by the following formula occurs at the electrode interface on the oxidant electrode side during fuel cell operation.
2H ₂ O → O ₂ + 4H ⁺ + 4e−

  As can be seen from the above equation, in the water electrolysis operation, hydrogen is not generated at the electrode interface on the oxidant electrode side during the fuel cell operation. Therefore, there is no possibility of mixing fuel and oxidant. The hydrogen ions (protons) generated by this reaction are taken into the electrolyte membrane at the time of the reaction and move toward the fuel electrode side (hydrogen side) during fuel cell operation, and the fuel during fuel cell operation Hydrogen molecules are not formed until they are combined with electrons supplied from an external power source at the electrode interface on the pole side (hydrogen side).

  Here, the proton transport phenomenon in the membrane is simply shown in FIG. The proton moves through the membrane through the sulfonic acid group while accompanying several water molecules. For this reason, when the sulfonic acid group is substituted with other ions (impurities here), the ion does not function as an ion exchange group, so that the conductivity of hydrogen ions is lowered, and as a result, the output voltage is lowered. The substituted impurities are stronger than hydrogen ions and cannot be eliminated in normal operation, but they can also be eliminated by increasing the amount of protons moving through the membrane several times and reversing the proton flow direction. It becomes easy.

  In general, in a fuel cell operation, a diffusion overvoltage caused by gas diffusibility is generated with an increase in current density. If the current density is further increased from this state, the voltage suddenly drops, and the operation itself becomes impossible.

In contrast, in the water electrolysis operation, the above problem is not caused even at a current density of several A / cm ² , which is generally several times that during fuel cell operation, and stable operation is possible. In other words, in the present invention, it is possible to pass a current in the direction opposite to that during fuel cell operation, several times that during general fuel operation, and several tens times as much as that in the conventional technology. Thereby, discharge of contaminants when protons move through the membrane electrode assembly, that is, movement from the inside of the membrane to the outside of the membrane is promoted, and the fuel cell performance can be recovered.

  If hydrogen and oxygen generated during the water electrolysis operation are stored in a storage tank and the stored gas is used during the fuel cell operation, efficient operation can be performed.

  When pure water is supplied to the oxidant electrode side during fuel cell operation, pure water may also be supplied to the fuel electrode side during fuel cell operation. As a result, impurities discharged from inside the membrane of the polymer electrolyte fuel cell can be reliably discharged to the outside of the cell, and safety during water electrolysis operation is also increased.

  Moreover, it is preferable that the pure water used for electrolysis has a conductivity of 1 μS / cm or less and a TOC (Total Organic Carbon) of 1 ppm or less. Impurity ions in the membrane are replaced with protons in pure water due to concentration equilibrium (if there is a concentration difference, mass transfer occurs to reach the same concentration), so supplying such pure water with high purity The film itself also has a membrane cleaning effect.

  By the way, in order to efficiently discharge impurities in the film, it is ideal to perform performance recovery operation when the impurities are in the vicinity of the film surface. This is because the shorter the migration process of impurities, the easier the discharge out of the film. However, it is difficult to directly measure whether impurities are present near the film surface. In this regard, according to the inventors' knowledge, the evaluation index is the voltage value. Further, as a result of investigations by the inventors, it is ideal to perform the recovery operation when the voltage drops by 20 mV with respect to the initial voltage. It is thought that.

  Therefore, in the actual implementation of this method, for example, the voltage value during operation of the polymer electrolyte fuel cell is monitored, and when a voltage drop of 20 mV or more is detected with respect to the initial voltage value, the polymer electrolyte fuel cell is detected. It can be proposed that the operation of the solid polymer fuel cell according to the present invention is performed after the operation is stopped.

  According to the present invention, fuel cell performance can be safely, easily and reliably recovered without introducing fuel into the oxidizer electrode and performing various strict controls.

  FIG. 2 shows a basic configuration of a system according to the embodiment. Pipes 1, 2, 3, and 4 are connected to the fuel cell FC. The pipe 1 functions as a discharge path for hydrogen generated during the water electrolysis operation, and the pipe 2 functions as a discharge path for oxygen generated during the water electrolysis operation. The pipe 3 functions as a fuel discharge path during fuel cell operation, and the pipe 4 functions as an oxidant discharge path during fuel cell operation. The pipe 4 is used as a pure water supply path during the water electrolysis operation of the fuel cell FC.

  The fuel cell FC is connected with pipes 5 and 6 that serve as an inert gas supply path for purging and drying the inside of the battery.

  The pipe 1 is provided with a tank 11, and the pipe 2 is provided with a tank 12. These tanks 11 and 12 store pure water and function as humidification tanks during fuel cell operation, and also function as pure water storage tanks during water electrolysis operation. That is, during the water electrolysis operation, pure water stored in the tank 12 is supplied from the pipe 7 to the oxidant electrode side of the fuel cell FC via the pipe 7 via the pump 13.

  Corresponding valves V1 to V4 are provided in the pipes 5, 6, 7, and 4, respectively. These V1 to V4 are controlled to be opened and closed by the control device 14.

  Further, during the water electrolysis operation, an electric current is supplied from the external power source 15 to the fuel cell FC so that the water is electrolyzed. More specifically, a current is supplied to current collectors 25 and 26, which will be described later, so that a current in a direction opposite to that during fuel cell operation flows. The dry state of the fuel cell FC is measured by the resistance value measured by the resistance meter 16. The external power supply 15 and the resistance meter 16 are also controlled by the control device 14.

  The tank 11 is provided with a gas storage tank 17 via pipes 17 a and 17 b connected to the upper part of the tank 11, and the tank 12 has a gas storage via pipes 18 a and 18 b connected to the upper part of the tank 12. A tank 18 is provided. These gas storage tanks 17 and 18 store hydrogen and oxygen generated during water electrolysis operation, which is a performance recovery operation described later. The pipes 17a, 17b, 18a, 18b are provided with corresponding valves V11, V12, V13, V14, respectively.

  FIG. 3 shows the internal cross-sectional shape of the solid polymer fuel cell FC. The fuel cell FC has the same configuration as a general polymer electrolyte fuel cell. That is, the membrane electrode assembly 24 is constituted by the proton conductive solid polymer membrane 21 responsible for the reaction and the platinum electrode catalysts 22, 23 serving as electrode portions joined to both surfaces of the proton conductive solid polymer membrane 21. Has been. On both sides of the membrane electrode assembly 24, current collectors 25, 26 responsible for electron exchange and gas diffusion are arranged, and separators 27, 28 that form reaction fluid flow paths 27 a, 28 a are collected inside. The electric bodies 25 and 26 are disposed on both surfaces. With the above configuration, the smallest unit cell (single cell) is configured.

  The separators 27 and 28 are provided with voltage measuring terminals 29 and 30 for measuring the voltage.

  In order for the fuel cell FC having such a configuration to have a water electrolysis function, it is necessary to change the base on the oxidizer electrode side in the fuel cell to a specification that can withstand the operation state of water electrolysis. For example, as disclosed in Japanese Patent Application Laid-Open No. 2004-134134 and Japanese Patent Application Laid-Open No. 2007-12315, for example, a small amount of iridium (black) is mixed in the catalyst 23 of the platinum electrode, so There is a method in which the aqueous solution is adjusted and the current collector 26 and the separators 27 and 28 are plated with Pt. There is no need to change any other structure.

The fuel cell FC has the above configuration, and the following operation example will be described.
During the fuel cell operation, the valves V1 to V3 are closed and the valve V4 is opened. As shown in FIG. 4, the fuel is introduced into the pipe 1, the oxidant is introduced into the pipe 2, and the tanks 11 and 12 are humidified. After the operation, the fuel cell FC is supplied. Then, since a potential difference is generated between the current collectors 25 and 26, power generation can be performed by connecting the load 31.

  At this time, an amount of gas corresponding to the external load 31 is consumed in the fuel cell FC, and the gas not used in the reaction is discharged out of the system via the pipes 3 and 4. The gas that has not been consumed may be recirculated by providing a separate route. For example, the gas may be collected in the gas storage tanks 17 and 18.

  Next, the water electrolysis operation that is the performance recovery operation will be described. During the water electrolysis operation, the valves V1 and V2 are first closed, the valve V3 is opened, and the valve V4 is closed. The pure water stored in the tank 12 is sucked by the pump 13 and supplied through the pipe 4 to the oxidant electrode side during the fuel cell operation in the fuel cell FC, that is, to the current collector 26 side of the flow path 28a. The flow rate of pure water supplied at this time is preferably 100 times or more of the electrolyzed water. Then, the cathode of the external power supply 15 is connected to the current collector 25 and the anode is connected to the current collector 26 to supply current to the current collectors 25 and 26.

  Then, in the fuel cell FC, hydrogen and oxygen, which are gases corresponding to the current supplied from the external power source 15, are generated. The generated hydrogen is discharged through the pipe 1 and once introduced into the tank 11, where after gas-liquid separation is performed, the hydrogen is discharged out of the system. On the other hand, the generated oxygen is discharged through the pipe 2 and introduced into the tank 12, where after gas-liquid separation is performed, it is discharged out of the system.

  These generated gases are stored in gas storage tanks 17 and 18, respectively. That is, during the water electrolysis operation, the valves V11 and V13 are opened and the valves V12 and V14 are closed. Thus, hydrogen generated during the water electrolysis operation is stored in the gas storage tank 17 via the tank 11 and the pipe 17a, and oxygen generated during the water electrolysis operation is stored in the gas storage tank 18 via the tank 12 and the pipe 18a. Stored. By doing in this way, these can be reused as fuel and oxidant during the next fuel cell operation.

  In addition, when storing hydrogen and oxygen generated during the water electrolysis operation, it is preferable to store at a pressure of 50 kPa or more with respect to the operation pressure during the fuel cell operation. However, since the inventors can operate at 1 MPa during water electrolysis operation, a special booster is not necessary when storing at such a high pressure.

  When the fuel cell is operated, the valves V11 and V13 are closed and the valves V12 and V14 are opened, and hydrogen is supplied from the gas storage tank 17 to the fuel cell FC through the pipe 17b and the pipe 1, respectively. Oxygen as an oxidant is supplied from the tank 18 to the fuel cell FC through the pipe 18b and the pipe 2, respectively. In this case, the valves V12 and V14 are opened according to the amount of gas required in the fuel cell FC. Control the degree. For example, it can be proposed to adjust the openings of these valves V12 and V14 so that the outlet pressure of the fuel cell FC, that is, the pressure in the pipes 3 and 4 becomes a constant pressure.

  When storing hydrogen and oxygen generated during the water electrolysis operation, the capacities of the tanks 11 and 12 are set large without providing the dedicated gas storage tanks 17 and 18 as in the example of FIG. You may make it store the hydrogen and oxygen which generate | occur | produced at the time of water electrolysis operation in the upper part in 11 and 12. In this case, in order to supply hydrogen and oxygen to the fuel cell FC during fuel cell operation, the flow rate for adjusting the supply flow rate between the tanks 11 and 12 in the pipes 1 and 2 and the fuel cell FC. A regulating valve is required.

  Here, when switching from the water electrolysis operation to the fuel cell operation, as disclosed in Japanese Patent Application Laid-Open No. 2006-127807, an inert dry gas is introduced from the pipes 5 and 6, and the internal substrate of the fuel cell FC is introduced. This switching can be repeated safely and smoothly by appropriately drying. At this time, the value of the resistance meter 16 is used as an index for judging whether or not the internal substrate has been appropriately dried, and the output signal of the conductor resistance between the separators 27 and 28 is taken into the control device 17 and incorporated in advance. Switching is performed in sequence.

  As shown in FIG. 5, according to the present embodiment, it is not necessary to mix hydrogen into the oxidant electrode side during fuel cell operation. In addition, by circulating a sufficient amount of pure water for the water electrolysis reaction, no special control is required in the performance recovery process, and the fuel cell FC is damaged even if it is operated at any current density for any time. There is no. At this time, the purity (conductivity, organic components, etc.) of the pure water to be circulated is preferably as high as possible. However, if the conductivity is 1 μS / cm or less and the TOC is 1 ppm or less, the fuel cell performance is sufficiently recovered. To do.

Next, the effect of the present invention was verified using a fuel cell having an electrode area of 250 cm ² . This time, the fuel cell performance was temporarily reduced by operating under two conditions that accelerate the performance degradation revealed in recent research, and the extent to which the performance was recovered from this state by this method was verified. In addition, since each cell is partitioned off by a separator and the pollutant does not move directly to another cell, the verification was performed using a single cell here.

First, the start / stop cycle operation was examined. In other words, the start / stop cycle is 4 h, and 3 ppm of pure water is supplied as humidifying pure water by TOC so that the membrane is easily contaminated with impurities, and the operation temperature is 80 ° C. and the current density is 0.6 A / cm ^2. Carried out.

  An example of the result is shown in the left bar graph group in FIG. As seen in the figure, the voltage dropped to 682 mV with respect to the initial voltage value of 700 mV when the total operation time was 100 h and the number of start and stop times was 25. In this state, power generation was stopped and performance recovery operation (water electrolysis operation) was performed. Thereafter, the operation was switched by a predetermined method, and the fuel cell operation was performed again. As a result, the voltage value recovered to 698 mV. Thereafter, the same start / stop cycle operation was repeated, and the performance recovery operation was performed each time the voltage value decreased to 680 mV. As a result, the voltage value after the performance recovery operation continued to recover to 698 to 701 mV for about 1000 hours in total operation time and about 250 times in starting and stopping.

Here, in order to confirm the effect of performance recovery operation more directly, the internal resistance of the fuel cell during power generation was measured by the AC impedance method. The results are shown in FIG. FIG. 7 shows a complex impedance plot in which the measurement results are plotted on the real axis-imaginary axis coordinates, and according to this, it is one of the indexes representing the effective area of the catalyst in the state where the performance is lowered as compared with before being lowered. Although the activated overvoltage component (diameter of the semicircle) is increasing (black triangle plot in FIG. 7), it can be seen that the value is almost restored to the original value by the performance recovery operation (the white outline in FIG. 7). Square plot). Therefore, it can be seen that the effective surface area of the catalyst was recovered by the performance recovery operation of the present invention. The operating conditions for water electrolysis at this time were an operating temperature of 80 ° C., a current density of 1.0 A / cm ² , an amount of circulating water of 0.5 L / min, and an operating time of 1 h.

Next, the start / stop cycle operation at a low load in which the oxygen side potential is 800 mV or more was examined. That is, repeated operation was performed at a current density of 0.1 A / cm ² , a start / stop cycle of 4 h, and an operating temperature of 80 ° C. Under this condition, the operation was performed for 120 hours in total operation time and 30 operations for starting and stopping, and then the operation was performed with a current density of 0.6 A / cm ² , and the voltage values before and after the low load operation were compared. .

  As a result, as can be seen in the bar graph group on the right side in FIG. 6, it was 699 mV before the low load operation, but rapidly decreased to 652 mV after the low load operation. As a result of performance recovery operation from this state, it recovered to the initial performance of 697 mV. Prior to performing the performance recovery operation, an attempt was made to recover the performance by circulating pure water as disclosed in JP-A-2001-85037.

  As a result, the voltage value after circulating pure water at 80 ° C. only to the oxidant electrode side for 2 h was 681 mV, and it was confirmed that the water electrolysis operation had a performance recovery effect. Although JP 2001-85037A does not describe the operation until the fuel cell is operated after circulating the cleaning liquid, this method is disclosed in JP 2006-127807 A as described above. An operation with a drying operation as used was used.

  Even in this case, the internal resistance value of the fuel cell during power generation was measured by the AC impedance method as in the previous example. As shown in FIG. 8, even in this case, the activated overvoltage component increases in the state where the performance is lowered, and the value is decreased by the performance recovery operation. Therefore, the performance recovery operation has a recovery effect on the catalyst effective surface area. Reconfirmed.

  From the above results, it can be seen that the fuel cell performance can be maintained for a long time by alternately performing the fuel cell operation and the water electrolysis operation. As an example of the operation method, as described above, the hydrogen and oxygen generated during the performance recovery operation are stored in the gas storage tanks 17 and 18, and the stored gas is used during the fuel cell operation. Efficient operation is possible.

  As described above, when the recovery method of the present invention is carried out, several to several tens of times more protons are allowed to flow in the reverse direction than the amount of proton movement from the fuel electrode to the oxidant electrode during fuel cell operation. It is possible to discharge pollutants more powerfully and more quickly than in the prior art. For this reason, this method has the effect which improves durability rather than a prior art.

  In the above-described embodiment, pure water is supplied to the oxidant electrode side in the fuel cell operation of the fuel cell FC, that is, the current collector 26 side of the flow path 28a during the water electrolysis operation that is the performance recovery operation. However, pure water may be supplied not only to the oxidant electrode side but also to the fuel electrode side during the water electrolysis operation.

  This will be specifically described with reference to the drawings. In the example shown in FIG. 9, a pipe 41 is connected between the tank 11 and the pipe 3 in the system example shown in FIG. 41 is provided with a pump 42 and a valve V6, and a pipe 3 is provided with a valve V7. With this configuration, pure water in the tank 11 is purified by the pump 42 via the pipe 41 and the pipe 3 to the fuel electrode side of the fuel cell FC, that is, to the current collector 25 side of the flow path 27a shown in FIG. Water can be supplied.

  During the water electrolysis operation, the valves V1 and V2 are first closed, the valves V3 and V6 are opened, and the valves V4 and V7 are closed. The pure water stored in the tank 12 is supplied by the pump 13 to the oxidant electrode side during the fuel cell operation in the fuel cell FC, that is, to the current collector 26 side of the flow path 28 a through the pipe 4 and stored in the tank 11. Pure water is supplied by the pump 42 to the fuel electrode side during the fuel cell operation in the fuel cell FC, that is, to the current collector 25 side of the flow path 27a through the pipe 3. At this time, as described above, the cathode of the external power source 15 is connected to the current collector 25 and the anode is connected to the current collector 26 to supply current to the current collectors 25 and 26.

  As described above, by supplying pure water not only to the oxidant electrode side but also to the fuel electrode side during the water electrolysis operation, impurities can be more reliably discharged out of the cell. That is, the impurities discharged from the membrane in the water electrolysis operation are first discharged to the flow path 27a through the current collector 25 on the fuel electrode side, and then discharged to the outside of the cell. If the fuel cell operation is started in a state where it is not discharged and remains inside the cell, the impurities once discharged from inside the film may enter the film again. Therefore, by circulating pure water also on the fuel electrode side, an action of washing the membrane surface is added, and impurities discharged from inside the membrane can be surely discharged to the outside of the cell.

  In addition, when pure water is supplied not only to the oxidant electrode side but also to the fuel electrode side, the safety of the water electrolysis operation (recovery operation) is enhanced. That is, in the water electrolysis operation, pure water for electrolysis is required, but this pure water also serves to remove (cool) the heat generated during the electrolysis reaction to the outside of the cell. Here, if the supply of pure water to the oxidant electrode side is stopped due to a failure of the pump 13 or the like, there will be no electrolysis, so the water in the membrane will start to decompose. Since the resistance value of the film depends on the wet state of the film, the resistance increases and the Joule heat increases as the film dries. However, since there is no pure water, heat cannot be removed outside the cell, and heat is trapped inside. The heat-resistant temperature of the film is said to be around 100 ° C., and when it exceeds that, the film starts to melt. Then, the sealing property between the fuel electrode side and the oxidant electrode side, which the membrane should originally perform, is lost, and the gases of both electrodes are mixed to form a short circuit state (= battery damage). As shown in FIG. 9, by supplying pure water also to the fuel electrode side, pure water in the fuel electrode side flow path 27a is subjected to electrolysis, and such a situation does not occur. . Therefore, the water electrolysis operation (recovery operation) can be performed more safely.

  When switching from the fuel cell operation to the water electrolysis operation, for example, the voltage value during operation of the fuel cell FC is monitored, and the performance recovery operation standby state is detected when a voltage drop of 20 mV or more is detected with respect to the initial voltage value. Then, after stopping the fuel cell operation of the fuel cell FC, switching to the water electrolysis operation makes it possible to efficiently and appropriately perform the performance recovery operation. Such switching control can be easily performed automatically by the control device 14 based on a detection signal from an appropriate voltage sensor that detects and monitors the voltage value of the fuel cell FC.

  Furthermore, when returning from the water electrolysis operation which is the performance recovery operation to the fuel cell operation again, for example, when performing the water electrolysis operation by supplying pure water having a conductivity of 1 μS / cm or less and a TOC of 1 ppm or less, It can be proposed to return to fuel cell operation after operating for about 1 hour at twice the current density during battery operation. Thus, during water electrolysis operation, it is preferable to perform water electrolysis with a larger current density than during fuel cell operation.

  The present invention is useful in restoring the performance of a polymer electrolyte fuel cell.

It is explanatory drawing which showed typically the transport phenomenon of the proton in a film | membrane. It is explanatory drawing which shows the piping system of the polymer electrolyte fuel cell used by embodiment. It is explanatory drawing which showed typically the internal structure of the polymer electrolyte fuel cell used in embodiment. It is explanatory drawing which showed typically the mode at the time of the fuel driving | operation of the polymer electrolyte fuel cell used by embodiment. It is explanatory drawing which showed typically the mode at the time of the water electrolysis driving | operation of the polymer electrolyte fuel cell used in embodiment. It is a graph which shows the output voltage before and after a performance fall test and after a performance recovery driving | operation. It is a graph based on the complex impedance plot which shows the internal resistance ratio before and after the driving performance degradation test when the current density is 0.6 A / cm ² and after the performance recovery driving. It is a graph based on the complex impedance plot which shows the internal resistance ratio before and after the performance deterioration test when the current density is 0.1 A / cm ² and after the performance recovery operation. It is explanatory drawing which shows the piping system of the polymer electrolyte fuel cell used by other embodiment.

Explanation of symbols

1, 2, 3, 4, 5, 6, 7, 17a, 17b, 18a, 18b, 41
Piping 11, 12 Tank 13, 42 Pump 14 Control device 15 External power supply 16 Resistance meter 17, 18 Gas storage tank 21 Proton conductive solid polymer membrane 22, 23 Catalyst 24 Membrane electrode assembly 25, 26 Current collector 27, 28 Separator 27a, 28a Flow path 31 Load FC Fuel cell

Claims (5)

A method for recovering the performance of a polymer electrolyte fuel cell, comprising:
In the polymer electrolyte fuel cell, supplying pure water to the oxidant electrode side during fuel cell operation,
A water electrolysis operation in which power is supplied from an external power source to electrolyze the pure water so that a current in a direction opposite to that during fuel cell operation flows is applied to the current collector of the polymer electrolyte fuel cell. A method for recovering the performance of a polymer electrolyte fuel cell, comprising recovering the performance of the polymer electrolyte fuel cell. 2. The performance recovery of a polymer electrolyte fuel cell according to claim 1, wherein hydrogen and oxygen generated during water electrolysis operation are stored in a storage tank, and the stored gas is used during fuel cell operation. Method. The pure water is also supplied to the fuel electrode side during the fuel cell operation when the pure water is supplied to the oxidant electrode side during the fuel cell operation. The solid polymer fuel cell performance recovery method as described. The method for recovering the performance of a polymer electrolyte fuel cell according to any one of claims 1 to 3, wherein the pure water has a conductivity of 1 µS / cm or less and a TOC of 1 ppm or less. The voltage value during operation of the polymer electrolyte fuel cell is monitored, and when the voltage drop of 20 mV or more is detected with respect to the initial voltage value, the operation of the polymer electrolyte fuel cell is stopped, and thereafter 4. A method for recovering the performance of a polymer electrolyte fuel cell, comprising performing the method for recovering the performance of a polymer electrolyte fuel cell according to any one of 3 above.

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