JP2009104919A - Method for operating solid polymer fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow the economical aging to be achieved by performing the excellent aging treatment in a short time, while reducing consumption of hydrogen as much as possible. <P>SOLUTION: The method has a first aging step to perform the hydrogen pump operation that the humidified hydrogen permeates a solid polymer electrolyte membrane 14 to be transferred to a cathode side of a fuel cell 10 with the maximum usable current density by feeding the humidified hydrogen to an anode side of the fuel cell 10 without feeding oxidizer gas to the cathode side of the fuel cell 10 while applying the positive pole potential to the anode side of the fuel cell 10 and applying the negative pole potential to the cathode side of the fuel cell 10, and a second aging step to perform power generation of the fuel cell 10 with the maximum usable current density after the first aging step. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for operating a polymer electrolyte fuel cell having an electrolyte membrane / electrode structure in which a pair of electrodes are disposed on both sides of an electrolyte membrane.

  A fuel cell supplies a fuel gas (mainly hydrogen-containing gas) and an oxidant gas (mainly oxygen-containing gas) to the anode-side electrode and the cathode-side electrode and causes them to react electrochemically. It is a system that obtains electrical energy.

  For example, in a polymer electrolyte fuel cell, an electrolyte membrane / electrode structure (MEA) provided with an anode electrode and a cathode electrode on both sides of an electrolyte membrane made of a polymer ion exchange membrane is sandwiched by separators. Has a cell. This type of power generation cell is normally used as a fuel cell stack mounted on a vehicle such as an automobile, for example, by laminating a predetermined number of electrolyte membrane / electrode structures and separators.

  In this type of polymer electrolyte fuel cell, the initial power generation performance is low because the water content of the electrolyte membrane immediately after assembly is not sufficient. Therefore, usually, the aging operation of the fuel cell is performed in order to obtain a desired power generation performance after the assembly of the fuel cell.

  For example, in the method of operating a fuel cell disclosed in Patent Document 1, the utilization rate of consumed gas is set so that flooding occurs in the fuel cell when the fuel cell is preliminarily operated (aging operation). It is characterized by improving.

  However, in the above operating method, since rapid flooding is involved, the control for suppressing the deterioration of the battery performance becomes complicated, and in particular, the performance of the electrolyte membrane constituting the MEA may be adversely affected.

  Further, when a hydrocarbon material, for example, is used as the electrolyte membrane constituting the MEA instead of the fluorine-based material, the hydrophobicity is higher than that of the fluorine-based material, and water sufficiently penetrates into the electrolyte membrane. There is a problem that it takes time to make it happen.

  Therefore, in the solid polymer fuel cell aging device disclosed in Patent Document 2, a loader that consumes a load current from the polymer electrolyte fuel cell during preliminary operation, the polymer electrolyte fuel cell, Control means connected between the loader and periodically changing the magnitude of the load current with time.

  Thereby, since the magnitude | size of load current is fluctuate | varied periodically with progress of time, the penetration | invasion promotion effect of the water to MEA increases, and it is supposed that the time required for an aging driving | operation can be shortened.

JP 2003-217622 A JP 2007-66666 A

  In the above-mentioned Patent Document 2, the cathode gas is supplied to the cathode, the anode gas is supplied to the anode, and a load current whose magnitude varies periodically with the passage of time from the fuel cell stack to the loader is supplied. Aging operation has started.

  However, the MEA that is used for the first time after assembly cannot generate power with a high current density. For this reason, it is necessary to gradually increase the amount of applied current from a low current density or shorten the holding time during load application to return to OCV (open circuit voltage).

  As a result, a considerable time is required until the power generation performance of the fuel cell is saturated, and there is a problem that it takes time for the aging operation. Moreover, during the aging operation, the cathode gas and the anode gas are consumed, and there is a problem that the amount of hydrogen used is excessive and extremely uneconomical.

  The present invention solves this type of problem, and is a solid polymer fuel cell capable of performing aging treatment satisfactorily in a short period of time while preventing hydrogen consumption as much as possible and performing economic aging. The purpose is to provide a driving method.

  The present invention relates to a method for operating a polymer electrolyte fuel cell for aging a polymer electrolyte fuel cell having an electrolyte membrane / electrode structure in which a pair of electrodes are disposed on both sides of the electrolyte membrane.

  In this operation method, in a state where a potential is applied to the polymer electrolyte fuel cell, without supplying the oxidant gas to one electrode side, by supplying humidified hydrogen to the other electrode side, A first aging step in which a hydrogen pump operation in which the hydrogen permeates through the electrolyte membrane and is transferred to the one electrode side is performed at a maximum current density or more during use; and after the first aging step, the solid polymer And a second aging step for generating electric power of the fuel cell at the maximum current density or higher.

  The electrolyte membrane is preferably composed of a hydrocarbon-based electrolyte membrane.

  Furthermore, it is preferable to apply a negative potential to the cathode, which is one electrode, and to apply a positive potential to the anode, which is the other electrode.

  In the present invention, first, a first aging process is carried out by so-called hydrogen pump operation in which a voltage is applied from the outside to move hydrogen ions in the electrolyte membrane, so that only hydrogen with low overvoltage is involved in the reaction. A large current (above the maximum current density during use) can be applied continuously below the corrosion potential. Therefore, it is possible to easily suppress the performance deterioration and shorten the time. In addition, in the hydrogen pump, hydrogen transferred to one electrode side does not react with the oxidant gas. For this reason, hydrogen is not consumed during the first aging step, which is extremely economical.

  Furthermore, since the second aging operation by power generation is performed after the first aging step by the hydrogen pump operation is performed, power generation with a high load (large current) is possible. As a result, the time until the completion of aging is shortened at once, hydrogen consumption can be prevented as much as possible, economical aging can be performed, and the catalytic activity of the fuel cell can be satisfactorily extracted.

  FIG. 1 is a schematic configuration diagram of an aging device 12 for performing a first aging process by a hydrogen pump operation in an operation method of a polymer electrolyte fuel cell 10 according to an embodiment of the present invention.

  As shown in FIG. 2, the fuel cell 10 includes, for example, an electrolyte membrane / electrode structure 20 in which a hydrocarbon-based solid polymer electrolyte membrane 14 is sandwiched between an anode-side electrode 16 and a cathode-side electrode 18, and the electrolyte The membrane / electrode structure 20 is sandwiched between the anode side separator 22 and the cathode side separator 24. The anode-side separator 22 and the cathode-side separator 24 are constituted by a carbon plate or a metal plate, and are provided with a seal member (not shown). The solid polymer electrolyte membrane 14 may be a fluorine-based membrane such as perfluorocarbon, for example.

  A fuel gas channel 26 is formed between the electrolyte membrane / electrode structure 20 and the anode side separator 22, and an oxidant is provided between the electrolyte membrane / electrode structure 20 and the cathode side separator 24. A gas flow path 28 is formed.

  As shown in FIG. 1, the fuel cell 10 supplies a fuel gas inlet communication hole 30 a for supplying a fuel gas such as a hydrogen-containing gas to one end side and an oxidant gas such as air (oxygen-containing gas). The oxidant gas inlet communication hole 32a is formed. On the other end side of the fuel cell 10, a fuel gas outlet communication hole 30b for discharging the fuel gas and an oxidant gas outlet communication hole 32b for discharging the oxidant gas are formed.

  The aging device 12 includes an anode side piping system 34 that supplies humidified hydrogen to the anode side (fuel gas flow path 26 side) of the fuel cell 10, and the cathode side (oxidant gas flow path 28 side) of the fuel cell 10. A direct-current power supply 38 that applies a negative electrode potential to the cathode side of the fuel cell 10, and a aging power source that applies a positive electrode potential to the anode side of the fuel cell 10. And a controller 40 that controls the entire apparatus 12.

The anode side piping system 34 includes a hydrogen cylinder 42 that stores hydrogen, and the hydrogen cylinder 42 communicates with the fuel gas inlet communication hole 30 a of the fuel cell 10 via the anode supply pipe 44. The anode supply pipe 44 is provided with an on-off valve 46a and a humidifier 48 from the hydrogen cylinder 42 side toward the downstream side. The humidifier 48 has an inert gas such as nitrogen gas (N ₂ gas). ) Is connected via an on-off valve 46b.

  The anode side piping system 34 includes an anode discharge piping 52 that communicates with the fuel gas outlet communication hole 30 b of the fuel cell 10. The anode discharge pipe 52 is provided with an on-off valve 46 c, and both ends of a bypass line 54 are connected to the anode discharge pipe 52 and the anode supply pipe 44. The bypass line 54 is provided with an on-off valve 46d.

  The cathode side piping system 36 includes a cathode supply pipe 58, and one end of the cathode supply pipe 58 can be connected to the anode supply pipe 44 via an on-off valve 46e. The other end of the cathode supply pipe 58 communicates with the oxidant gas inlet communication hole 32 a of the fuel cell 10.

  The cathode side piping system 36 is provided with a cathode discharge pipe 60 that communicates with the oxidant gas outlet communication hole 32 b of the fuel cell 10, and this cathode discharge pipe 60 is connected to the upstream side of the on-off valve 46 c with respect to the anode discharge pipe 52. Is done.

  FIG. 3 is a schematic configuration diagram of a power generation aging device 70 for performing the second aging process on the fuel cell 10 after the first aging process by the aging device 12. The power generation aging device 70 may be configured as a dedicated machine used for power generation aging, or may be configured to perform power generation aging by a fuel cell system incorporating the fuel cell 10 for in-vehicle use. .

  The power generation aging device 70 includes a fuel gas supply system 72 for supplying fuel gas to the fuel cell 10, an oxidant gas supply system 74 for supplying oxidant gas to the fuel cell 10, and the fuel cell 10. And an electronic load 76 to be connected.

  The fuel gas supply system 72 includes a hydrogen tank 78, and hydrogen gas is supplied from the hydrogen tank 78 through the hydrogen supply pipe 80 to the fuel gas inlet communication hole 30 a, and a variable valve is provided in the hydrogen supply pipe 80. 82a is disposed.

  The fuel gas supply system 72 has a hydrogen discharge pipe 84 that communicates with the fuel gas outlet communication hole 30 b, and a bypass line 86 is connected to the hydrogen discharge pipe 84 and the hydrogen supply pipe 80. On-off valves 88 a and 88 b are disposed in the hydrogen discharge pipe 84 and the bypass line 86.

  The oxidant gas supply system 74 includes an air pump (air compressor) 90, and an air supply pipe 92 connected to the air pump 90 is connected to the oxidant gas inlet communication hole 32a. The air supply pipe 92 is provided with a variable valve 82b.

  The oxidant gas supply system 74 includes an air discharge pipe 94 connected to the oxidant gas outlet communication hole 32 b, and a bypass line 96 is connected to the air discharge pipe 94 and the air supply pipe 92. The air discharge pipe 94 and the bypass line 96 are provided with on-off valves 88c and 88d.

  The electronic load 76 has a variable resistance function, and the resistance value can be set so that the output current of the fuel cell 10 is 0 or more than the maximum current density at the time of use. The maximum current density is a level at which the solid polymer electrolyte membrane 14 is not deteriorated by heat generation, and is a maximum of 200%, preferably 150% or less (more preferably 125%).

  The operation method by the aging device 12 and the power generation aging device 70 configured as described above will be described below along the flowchart shown in FIG.

  First, as shown in FIG. 1, after the fuel cell 10 is attached to the aging device 12, before the so-called hydrogen pump operation is started, a purge process with nitrogen gas is performed (step S <b> 1). The nitrogen cylinder 50 is provided in the anode side piping system 34, and the on / off valves 46b, 46c and 46e are opened, and the on / off valves 46a and 46d are closed.

  For this reason, the nitrogen gas led out from the nitrogen cylinder 50 is humidified through the humidifier 48 and then is divided into the anode supply pipe 44 and the cathode supply pipe 58. The humidified nitrogen gas is supplied to the fuel gas inlet communication hole 30a and the oxidant gas inlet communication hole 32a of the fuel cell 10.

  In the fuel cell 10, as shown in FIG. 2, humidified nitrogen gas is introduced into the fuel gas channel 26 and the oxidant gas channel 28. The air remaining in the fuel gas channel 26 and the oxidant gas channel 28 is replaced with nitrogen gas by scavenging for a predetermined time.

  Next, the on-off valve 46b is closed and the on-off valve 46a is opened. Accordingly, hydrogen gas is led out from the hydrogen cylinder 42, and after being humidified by the humidifier 48, the hydrogen gas is divided into the anode supply pipe 44 and the cathode supply pipe 58. Therefore, in the fuel cell 10, the fuel gas channel 26 and the oxidant gas channel 28 are scavenged with hydrogen gas (step S2).

  Furthermore, it progresses to step S3 and the 1st aging process by a hydrogen pump driving | operation is started. In this hydrogen pump operation, as shown in FIG. 1, a positive potential is applied to the anode side (anode side electrode 16) and a negative potential is applied to the cathode side (cathode side electrode 18). .

  In this state, in the cathode side piping system 36, the on-off valve 46e is closed. On the other hand, in the anode side piping system 34, the on-off valves 46b and 46d are closed and the on-off valves 46a and 46c are opened. Accordingly, hydrogen gas is supplied from the hydrogen cylinder 42 to the anode supply pipe 44, and this hydrogen gas is humidified by the humidifier 48 and then passes through the fuel gas inlet communication hole 30 a of the fuel cell 10 to the fuel gas flow path 26. Supplied.

Here, in the fuel cell 10, a positive electrode potential is applied to the anode side via the DC power supply 38, and a negative electrode potential is applied to the cathode side. Therefore, as shown in FIG. 5, the reaction of H ₂ → 2H ⁺ + 2e ⁻ occurs in the anode side electrode 16, and hydrogen ions (H ⁺ ) permeate the solid polymer electrolyte membrane 14 and become the cathode side electrode 18. Move to. The cathode side electrode 18 causes a reaction of 2H ⁺ + 2e ⁻ → H ₂ .

  Accordingly, protons (hydrogen ions) move from the anode side electrode 16 to the cathode side electrode 18 and entrained water is supplied to the solid polymer electrolyte membrane 14, and the water content of the solid polymer electrolyte membrane 14 increases. .

  The unreacted portion of the hydrogen gas supplied to the fuel gas flow path 26 of the fuel cell 10 is discharged from the fuel gas outlet communication hole 30b to the anode discharge pipe 52. On the other hand, the hydrogen gas in the oxidant gas passage 28 is discharged from the oxidant gas passage 28 through the oxidant gas outlet communication hole 32 b to the anode discharge pipe 52 from the cathode discharge pipe 60.

  In this case, in the above-described hydrogen pump operation, the stoichiometry of hydrogen introduced from the hydrogen cylinder 42 is set to be relatively high, and the amount of moisture introduced can be increased.

  Moreover, the current density applied by the DC power supply 38 is set to the maximum current density during use. This is because in the hydrogen pump operation, only hydrogen with a small overvoltage is involved in the reaction, so that a large current can be drawn at the early stage of aging. This shortens the aging time.

  Further, since the cathode side electrode 18 side is not affected by the concentration overvoltage due to the diffusion resistance of the reaction gas, it is possible to reduce deterioration due to local reaction concentration on the electrode surface and the distribution of the aging state. Therefore, the electrode surface can be aged uniformly.

  Furthermore, in the case of aging by normal power generation, since a constant current cannot be maintained during aging, the aging is performed by cycling the load current. For this reason, the high potential cycle is repeated, which may induce corrosion of the catalyst alone.

  On the other hand, in aging by hydrogen pump operation, since a large current can be continuously applied at a corrosion potential or lower, it is possible to easily suppress performance deterioration and shorten the aging time. At that time, in the hydrogen pump operation, the hydrogen transferred to the cathode side electrode 18 does not react with the oxidant gas and is discharged to the anode discharge pipe 52 as hydrogen gas. Thereby, there is an effect that hydrogen is not consumed and is extremely economical.

  Further, in the aging by the hydrogen pump operation, the heat generation amount due to the overvoltage loss is reduced, so that the temperature degradation of the solid polymer electrolyte membrane 14 can be effectively suppressed.

  By the way, there is a possibility that the catalyst activity cannot be sufficiently extracted by aging only by the hydrogen pump operation. Therefore, in this embodiment, the 2nd aging process by power generation aging is performed after the 1st aging process by hydrogen pump operation (refer to Step S4 and Drawing 6).

  First, as shown in FIG. 3, the fuel cell 10 after the first aging process is attached to the power generation aging device 70. Therefore, the hydrogen tank 78 constituting the fuel gas supply system 72 supplies the fuel gas to the fuel gas inlet communication hole 30 a via the hydrogen supply pipe 80. On the other hand, air is supplied from the air supply pipe 92 to the oxidant gas inlet communication hole 32 a via the air pump 90 constituting the oxidant gas supply system 74.

  Therefore, as shown in FIG. 2, hydrogen gas is supplied to the fuel gas passage 26 and air is supplied to the oxidant gas passage 28, and an electrochemical reaction is generated by the electrolyte membrane / electrode structure 20. . Specifically, as shown in FIG. 7, protons (hydrogen ions) generated at the anode side electrode 16 pass through the solid polymer electrolyte membrane 14 and move to the cathode side electrode 18. Water is produced.

  Therefore, power generation by the fuel cell 10 is started, and the current output from the fuel cell 10 via the electronic load 76 is controlled to increase or decrease as shown in FIG. Thus, power generation aging is performed. For example, when a predetermined time has elapsed (YES in step S5), the aging operation of the fuel cell 10 is completed.

  Thus, in the present embodiment, the aging process of the newly assembled fuel cell 10 is first performed by the first aging process by the hydrogen pump operation and the second aging process by the power generation aging.

  In the aging by the hydrogen pump operation, water is surely drawn into the proton channel by applying a large current, and uniform aging treatment is performed in the electrode surface by reducing the overvoltage.

  In addition, since the catalyst of the cathode side electrode 18 is reduced with hydrogen, the oxide film is removed and the bonding property with the catalyst interface is improved. In addition, there is an advantage that the exchange of protons can be promoted by improving the bondability between the solid polymer electrolyte membrane 14 and the electrolyte interface in the catalyst layer.

  By performing power generation aging after performing aging by this hydrogen pump operation, this power generation aging enables high-load power generation. For this reason, it is not necessary to gradually increase the output current from a low current as in the case of performing only the conventional power generation aging, and the time until the aging is completed is shortened at once.

  As a result, the consumption of hydrogen can be prevented as much as possible, an economic aging process can be performed, and the catalyst activity of the fuel cell 10 can be satisfactorily brought out.

  FIG. 8 is a result of comparison of power generation performance in the aging by only the hydrogen pump operation and the present embodiment in which the aging by the hydrogen pump operation and the power generation aging are combined. Thereby, compared with the aging only by hydrogen pump operation, in this embodiment, the result that the catalyst activity of the fuel cell 10 can be fully drawn out like a normal aging completion product was obtained.

  In this embodiment, a positive electrode potential is applied to the anode side, a negative electrode potential is applied to the cathode side, and humidification is applied to the anode side without supplying an oxidant gas to the cathode side. The supplied hydrogen is supplied to operate the hydrogen pump. On the other hand, a positive electrode potential was applied to the cathode side, a negative electrode potential was applied to the anode side, and the cathode side was humidified without supplying an oxidant gas to the anode side. Hydrogen pump operation can also be performed by supplying hydrogen.

1 is a schematic configuration diagram of an aging device for performing a first aging step by a hydrogen pump operation in a method for operating a polymer electrolyte fuel cell according to an embodiment of the present invention. 2 is a cross-sectional explanatory view of the fuel cell. FIG. It is a schematic block diagram of the electric power generation aging apparatus for performing a 2nd aging process with respect to the said fuel cell. It is a flowchart explaining the said driving | running method. It is explanatory drawing of the aging by a hydrogen pump driving | operation. It is explanatory drawing of the said operating method. It is explanatory drawing of electric power generation aging. It is comparison explanatory drawing of the performance by various aging.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel cell 12 ... Aging apparatus 14 ... Solid polymer electrolyte membrane 16 ... Anode side electrode 18 ... Cathode side electrode 20 ... Electrolyte membrane and electrode structure 26 ... Fuel gas flow path 28 ... Oxidant gas flow path 30a ... Fuel gas Inlet communication hole 30b ... Fuel gas outlet communication hole 32a ... Oxidant gas inlet communication hole 32b ... Oxidant gas outlet communication hole 34 ... Anode side piping system 36 ... Cathode side piping system 38 ... DC power supply 40 ... Controller 42 ... Hydrogen cylinder 44 Anode supply pipe 48 Humidifier 50 Nitrogen cylinder 52 Anode discharge pipe 58 Cathode supply pipe 70 Power generation aging device 72 Fuel gas supply system 74 Oxidant gas supply system 76 Electronic load 78 Hydrogen tank 80 Hydrogen supply pipe 84 ... Hydrogen discharge pipe 90 ... Air pump 92 ... Air supply pipe 94 ... Air discharge pipe

Claims (3)

A method for operating a polymer electrolyte fuel cell for aging a polymer electrolyte fuel cell having an electrolyte membrane / electrode structure in which a pair of electrodes are disposed on both sides of the electrolyte membrane,
By supplying humidified hydrogen to the other electrode side without supplying an oxidant gas to one electrode side in a state where a potential is applied to the polymer electrolyte fuel cell, the hydrogen is A first aging step of performing a hydrogen pump operation that passes through the electrolyte membrane and is transferred to the one electrode side at a current density greater than or equal to the maximum current density during use;
After the first aging step, a second aging step in which power generation of the polymer electrolyte fuel cell is performed at the maximum current density or more,
A method for operating a polymer electrolyte fuel cell, comprising:   2. The method for operating a solid polymer fuel cell according to claim 1, wherein the electrolyte membrane is composed of a hydrocarbon-based electrolyte membrane.   3. The operation method according to claim 1, wherein a negative electrode potential is applied to the cathode which is the one electrode, and a positive electrode potential is applied to the anode which is the other electrode. A method for operating a polymer electrolyte fuel cell.

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