JP7500862B2 - Method for aging a fuel cell - Google Patents

Description

The present invention relates to a method for aging a fuel cell.

A fuel cell comprises a membrane electrode assembly (MEA) having an electrolyte membrane and a pair of electrodes laminated on each side of the electrolyte membrane, and a pair of separators (bipolar plates) installed on each of the electrode surfaces of the MEA. A number of such fuel cells are stacked together to assemble into a fuel cell stack. In the manufacture of a fuel cell stack (or fuel cell), aging is carried out after assembly to bring out the power generation performance of the fuel cell.

For example, JP 2020-57572 A discloses aging in which a manufactured fuel cell stack is placed in an aging booth and electricity is generated using an aging device (power generation device).

This type of aging humidifies the electrolyte membrane by supplying humidified hydrogen gas during power generation and allowing protons, which are formed when electrons are ionized from hydrogen, to pass through the electrolyte membrane. However, there is a trade-off between the supply of hydrogen gas and humidification; if the amount of water accompanying the hydrogen gas is increased, a liquid water film will form on the electrode, reducing gas diffusivity and reducing the amount of protons generated. Conversely, if the amount of water accompanying the hydrogen gas is reduced, the electrolyte membrane will not be sufficiently humidified.

The present invention has been made in consideration of the above-mentioned situation, and aims to provide a method for aging a fuel cell that can further promote humidification of the electrolyte membrane, thereby making aging more efficient.

In order to achieve the above-mentioned objective, one aspect of the present invention is a method for aging a fuel cell having an electrolyte membrane and a pair of electrodes provided on both sides of the electrolyte membrane, in which ultra-fine hydrogen bubble water containing hydrogen that can be separated into protons as ultra-fine bubbles is supplied to one electrode of the fuel cell, and ultra-fine bubble aging is performed in which the protons are transferred from the one electrode to the other electrode through the electrolyte membrane.

The above-mentioned fuel cell aging method can further promote humidification of the electrolyte membrane, thereby making aging more efficient.

1 is an explanatory diagram showing the overall configuration of an aging device that performs an aging method for a fuel cell according to an embodiment of the present invention; FIG. 2 is a perspective view showing the configuration of a fuel cell. 3A and 3B are explanatory diagrams showing a first and second pattern of UFB aging (concentration cell), respectively. FIG. 4 is an enlarged cross-sectional view showing the operation of a fuel cell in a first pattern of concentration cells. FIG. 4 is an enlarged cross-sectional view showing the operation of a fuel cell in a second pattern of concentration cells. Fig. 6A is a flowchart showing the aging method for a fuel cell according to the first embodiment, and Fig. 6B is a flowchart showing the process flow of UFB aging. FIG. 13 is a partial explanatory diagram showing an aging device according to a modified example. Fig. 8A is an explanatory diagram showing the configuration of a first supply processing unit of the aging device, and Fig. 8B is an explanatory diagram showing the configuration of a second supply processing unit of the aging device. 9A and 9B are explanatory diagrams showing a first and second patterns of the aging method (UFB aging: hydrogen pump) for a fuel cell according to the second embodiment, respectively. FIG. 4 is an enlarged cross-sectional view showing the operation of a fuel cell in a first pattern of the hydrogen pump. 10 is a flowchart showing an aging method for a fuel cell according to a third embodiment.

A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

First Embodiment
The aging method for a fuel cell 10 according to a first embodiment of the present invention uses an aging device 50 shown in Figure 1. A fuel cell stack 12, in which a plurality of fuel cells 10, which are unit power generation cells, are stacked, is set in the aging device 50. The aging device 50 performs ultra-fine bubble aging, in which a liquid containing ultra-fine bubbles (hereinafter sometimes abbreviated as UFB) is supplied to the fuel cell stack 12, thereby improving the power generation performance of the fuel cell stack 12. To facilitate understanding of the invention, the configuration of the fuel cell stack 12 will be first described below.

The fuel cell stack 12 is constructed by housing a stack 14 in which a plurality of fuel cells 10 are stacked in a stack case (not shown). As shown in FIG. 2, the fuel cell 10 has an electrolyte membrane electrode assembly 18 (hereinafter referred to as MEA 18) having a resin frame 19 on the outer periphery, and a first separator 20a and a second separator 20b stacked on both sides of the MEA 18. The fuel cell 10 generates electricity by an electrochemical reaction between the anode gas and the cathode gas by passing an anode gas (fuel gas) such as hydrogen between the first separator 20a and the MEA 18, while passing a cathode gas (oxidant gas) such as oxygen between the second separator 20b and the MEA 18.

The MEA 18 has an electrolyte membrane 22, an anode electrode 24 provided on one side of the electrolyte membrane 22, and a cathode electrode 26 provided on the other side of the electrolyte membrane 22. The electrolyte membrane 22 is, for example, a solid polymer electrolyte membrane (cation exchange membrane) that is a thin film of perfluorosulfonic acid containing moisture. In addition to a fluorine-based electrolyte, the electrolyte membrane 22 can also be an HC (hydrocarbon)-based electrolyte.

Each of the anode electrode 24 and the cathode electrode 26 has a catalyst layer 24a, 26a bonded to the electrolyte membrane 22, a dense carbon layer 24b, 26b laminated on the catalyst layer 24a, 26a, and a gas diffusion layer 24c, 26c laminated on the dense carbon layer 24b, 26b (see FIG. 4). The catalyst layer 24a, 26a is formed, for example, by uniformly applying porous carbon particles having a platinum alloy supported on the surface thereof together with an ion-conductive polymer binder onto the surface of carbon paper, carbon cloth, or the like. The catalyst layer 24a, 26a has a plurality of pores with an average diameter (average pore diameter) of about 50 to 80 nm. The dense carbon layer 24b, 26b is formed from carbon paper, carbon cloth, or the like, and has an average pore diameter of about 400 to 600 nm. The gas diffusion layer 24c is made of carbon paper or carbon cloth, and has an average pore size of about 30 to 50×10 ³ nm.

The first separator 20a and the second separator 20b are formed by pressing, for example, a steel plate, a stainless steel plate, an aluminum plate, a plated steel plate, or a metal plate with a corrosion-resistant surface treatment applied to the metal surface, to form an uneven cross section. In manufacturing the fuel cell stack 12, a joined separator is formed by joining the outer peripheries of the first separator 20a of one fuel cell 10 and the second separator 20b of another fuel cell 10, and the joined separator and the MEA 18 are stacked to construct the stack 14.

The first separator 20a has an anode flow path 30, which allows the anode gas to flow, on the surface facing the anode electrode 24 of the MEA 18. The anode flow path 30 is composed of linear flow grooves (or wavy flow grooves) formed between a plurality of protrusions 31 extending in the longitudinal direction of the first separator 20a.

The second separator 20b has a cathode flow path 32, through which the cathode gas flows, on the surface facing the cathode electrode 26 of the MEA 18 (for convenience, in FIG. 2, the flow direction of the cathode gas is illustrated on the cathode electrode 26). The cathode flow path 32 is composed of a linear flow groove (or a wavy flow groove) formed between a plurality of protrusions 33 extending in the longitudinal direction of the second separator 20b.

In addition, a refrigerant flow path 34 for circulating a refrigerant (e.g., water) is formed between the contacting surfaces of the first separator 20a and the second separator 20b. The refrigerant flow path 34 is formed by overlapping the back surface shape of the anode flow path 30 of the first separator 20a with the back surface shape of the cathode flow path 32 of the second separator 20b.

Furthermore, the fuel cell 10 has a plurality of fluid communication holes 36 that allow the anode gas, cathode gas and refrigerant to flow in the stacking direction of the stack 14.

At one end edge of the long side of the fuel cell 10, one anode gas inlet communication hole 38a, two cathode gas outlet communication holes 40b, and a refrigerant inlet communication hole 42a are provided as fluid communication holes 36. The anode gas inlet communication hole 38a communicates with the anode flow path 30 of the first separator 20a, and allows anode gas to flow into the anode flow path 30. The two refrigerant inlet communication holes 42a communicate with the refrigerant flow path 34 between the first and second separators 20a and 20b, and allow refrigerant to flow into the refrigerant flow path 34. The two cathode gas outlet communication holes 40b communicate with the cathode flow path 32 of the second separator 20b, and allow cathode gas to flow out from the cathode flow path 32.

At the other end edge of the long side of the fuel cell 10, one cathode gas inlet communication hole 40a, two anode gas outlet communication holes 38b, and two refrigerant outlet communication holes 42b are provided as fluid communication holes 36. The cathode gas inlet communication hole 40a communicates with the cathode flow path 32 of the second separator 20b, and allows the cathode gas to flow into the cathode flow path 32. The two refrigerant outlet communication holes 42b communicate with the refrigerant flow path 34 between the first and second separators 20a and 20b, and allow the refrigerant to flow out of the refrigerant flow path 34. The two anode gas outlet communication holes 38b communicate with the anode flow path 30 of the first separator 20a, and allow the anode gas to flow out of the anode flow path 30. The position, number, shape, etc. of the fluid communication holes 36 may be appropriately set according to the required specifications.

As shown in FIG. 1, at one end of the stack 14 in the stacking direction, a terminal plate 44a, an insulator 46a, and an end plate 48a are stacked outward in this order. At the other end of the stack 14 in the stacking direction, a terminal plate 44b, an insulator 46b, and an end plate 48b are stacked outward in this order. Each end plate 48a, 48b forms part of a stack case. Each of the fluid communication holes 36 described above is also formed through one end (or both ends) of the stack 14 in the stacking direction, and communicates with each pipe (not shown) attached to the outer surface of the end plate 48a.

Next, the aging device 50 according to this embodiment will be described. The aging device 50 has a placement section 52 for placing the fuel cell stack 12, a first circulation section 60 and a second circulation section 70 for circulating liquid through the fuel cell stack 12, and a voltage application section 80 for applying a potential to the fuel cell stack 12. The aging device 50 also has a control section 54 for controlling the operation of the entire device.

The arrangement section 52 has a space in which the fuel cell stack 12 can be set, and has a number of pipes (not shown) that can be connected to each of the fluid communication holes 36 of the set fuel cell stack 12 (end plate 48a). The aging device 50 also connects a pair of terminal plates 44a, 44b of the fuel cell stack 12 set in the arrangement section 52 to the voltage application section 80 via a pair of harnesses 56.

The first circulation section 60 has a first circulation path 61 for liquid that is connected to a specific pipe in the arrangement section 52. The first circulation path 61 is composed of a metal pipe or the like having a flow path on the inside, and is connected to the anode gas inlet communication hole 38a and the anode gas outlet communication hole 38b of the fuel cell stack 12 set in the arrangement section 52. In other words, the first circulation path 61 circulates liquid to the anode electrode 24 of the fuel cell 10 in the fuel cell stack 12.

The first circulation section 60 also circulates ultra-fine bubble water (UFB water), which is a liquid obtained by mixing ultra-fine bubbles (UFB) with water, to the anode electrode 24. For this reason, the first circulation section 60 includes a first ultra-fine bubble generating section (first UFB generating section 62) at a predetermined position on the first circulation path 61.

UFB refers to bubbles with a smaller bubble diameter than microbubbles (for example, bubbles with a bubble diameter smaller than 10 ³ nm). The first UFB generating unit 62 according to this embodiment generates UFB with an average bubble diameter of about 100 nm to 150 nm. UFB are negatively charged as negative colloids even in liquid, do not bond with each other, and are difficult to float, so they can remain in liquid for a long time without decreasing the bubble number density.

Specifically, the first UFB generating unit 62 has a mixing unit 63 that mixes UFB with the water circulating through the first circulation path 61, and two types of gas sources (H ₂ gas source 64, N ₂ gas source 65) connected to the mixing unit 63. The first UFB generating unit 62 supplies one of the two types of gas sources to the mixing unit 63, and generates UFB water having the UFB of the supplied gas in the mixing unit 63. That is, the first UFB generating unit 62 can selectively generate hydrogen ultra-fine bubble water (H ₂ UFB water) having hydrogen UFB (H ₂ UFB) and nitrogen ultra-fine bubble water (N ₂ UFB water) having nitrogen UFB (N ₂ UFB).

The mixing section 63 of the first UFB generating section 62 is provided in the vicinity of the supply port 52a that supplies UFB water to the placement section 52, and operates appropriately under the control of the control section 54. The configuration of the mixing section 63 is not particularly limited, and any well-known device capable of generating UFB water from the supplied gas and water may be applied. For example, the mixing section 63 may apply a pressurized dissolution method in which a solution in which gas is pressurized and dissolved in water is repeatedly sprayed and circulated under low pressure.

In addition to the first UFB generation unit 62, the first circulation unit 60 includes a first pump 66 that circulates the liquid, and a first valve 67 that opens and closes the flow path of the first circulation path 61. The first pump 66 circulates the liquid at an appropriate flow rate by having its rotation speed controlled by the control unit 54. The first valve 67 has its opening changed under the control of the control unit 54 to adjust the pressure of the liquid in the first circulation path 61 and to block the flow of the liquid in a closed state.

In addition, the first circulation path 61 is provided with a number of sensors (not shown) that detect information related to the circulation state of the liquid, and each sensor is connected to the control unit 54 so as to be able to communicate information. For example, the multiple sensors may include a pressure sensor that detects the pressure within the first circulation path 61, a flow sensor that detects the flow rate of the liquid, and an air bubble sensor or concentration sensor that detects the amount of UFB.

Furthermore, a first water supply unit 68 that supplies water to the first circulation path 61 and a first discharge path 69 that discharges liquid from the first circulation path 61 are connected to the first circulation path 61. The first water supply unit 68 is connected to city water, for example, and has a configuration of a water treatment unit that removes impurities, a tank, and a valve (both not shown), and supplies water to the first circulation path 61 under the control of the control unit 54. The first discharge path 69 has a first discharge valve 69a that opens and closes under the control of the control unit 54, and when the first discharge valve 69a is in a closed state, it blocks the discharge of liquid from the first circulation path 61, and when the first discharge valve 69a is in an open state, it discharges liquid from the first circulation path 61.

On the other hand, the second circulation section 70 has a second circulation path 71 for liquid that is connected to a specific pipe in the arrangement section 52. The second circulation path 71 is composed of a metal pipe or the like having a flow path on the inside, and is connected to the cathode gas inlet communication hole 40a and the cathode gas outlet communication hole 40b of the fuel cell stack 12 set in the arrangement section 52. In other words, the second circulation path 71 circulates liquid to the cathode electrode 26 of the fuel cell 10 in the fuel cell stack 12.

In the second circulation path 71, similar to the first circulation path 61, a mixing section 73, a second UFB generating section 72 having an _H2 gas source 74 and an _N2 gas source 75, a second pump 76, a second valve 77, and a plurality of sensors (not shown) are provided. In addition, a second water supply section 78 and a second discharge path 79 having a second discharge valve 79a are connected to the second circulation path 71. The second circulation section 70 may be configured in the same manner as the first circulation section 60, and operates under the control of the control section 54. Therefore, a detailed description will be omitted.

In addition, the voltage application unit 80 of the aging device 50 is electrically connected to a pair of terminal plates 44a, 44b of the fuel cell stack 12 arranged in the arrangement unit 52 via a harness 56, and is communicatively connected to the control unit 54. Under the control of the control unit 54, the voltage application unit 80 applies an appropriate potential to the anode electrode 24 and the cathode electrode 26 of each fuel cell 10.

Specifically, the voltage application unit 80 has a power supply unit 82, a switch unit 84, and a voltage control unit 86. The power supply unit 82 and the switch unit 84 configure an equivalent circuit in which the positive and negative poles of the two power supplies 82a and 82b connected in parallel are in the opposite directions, and each power supply can be switched between energized and cut off. Therefore, in the voltage application unit 80, when the switch unit 84 is switched by the control unit 54, one power supply 82a applies a negative potential to the anode electrode 24 of the fuel cell 10 compared to the other pole, and applies a positive potential to the cathode electrode 26. Conversely, in the voltage application unit 80, when the switch unit 84 is switched by the control unit 54, the other power supply 82b applies a positive potential to the anode electrode 24 and a negative potential to the cathode electrode 26 compared to the other pole.

The voltage control unit 86 of the voltage application unit 80 adjusts the voltage output to the fuel cell stack 12 when the power supply unit 82 is energized. The voltage value may be set to an appropriate value according to the number of stacked fuel cells 10, and is set so that the voltage per unit fuel cell (one cell) is in the range of several mV to approximately 1V, for example.

Furthermore, the aging device 50 has an electronic load section (electronic load device: not shown) that is electrically connected to the pair of terminal plates 44a, 44b of the fuel cell stack 12 via a harness 56 and is communicatively connected to the control section 54. The electronic load section is used to pass a large current between the anode and cathode particularly during power generation (power generation aging or power generation for characteristic evaluation), and passes an appropriate current between the anode electrode 24 and the cathode electrode 26 of each fuel cell 10 under the control of the control section 54.

Although not shown in the figure, the aging device 50 may be provided with a refrigerant circulation section that circulates refrigerant (water) through the refrigerant outlet communication hole 42b, the refrigerant inlet communication hole 42a, and the refrigerant flow path 34 of the fuel cell stack 12 arranged in the arrangement section 52.

The control unit 54 of the aging device 50 has one or more processors, a memory, an input/output interface, and an electronic circuit (all not shown). The one or more processors execute a program (not shown) stored in the memory, forming multiple functional blocks in the control unit 54 for controlling each component of the fuel cell system. At least a portion of each functional block may be formed by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array), or an electronic circuit including a discrete device. The memory may also be associated with the processor, integrated circuit, etc.

Here, the aging method for the fuel cell 10 according to the first embodiment utilizes the principle of a concentration cell in order to pass protons (H ⁺ ) through the MEA 18 during UFB aging. The concentration cell creates a hydrogen (H ₂ ) concentration difference between the anode electrode 24 and the cathode electrode 26 of the MEA 18 by using H ₂ UFB water supplied to the fuel cell 10, and promotes concentration equilibration within the MEA 18, thereby moving the protons.

The control unit 54 controls the operation of the first circulating unit 60, the second circulating unit 70, and the voltage applying unit 80, thereby enabling two patterns of UFB aging (concentration cell) to be performed, as shown in Figures 3A and 3B. The first pattern is a supply application pattern in which _H2UFB water is supplied to the anode electrode 24 and a negative potential is applied to it compared to the other electrode, while _N2UFB water is supplied to the cathode electrode 26 and a positive potential is applied to it. The second pattern is a reverse supply application pattern in which _N2UFB water is supplied to the anode electrode 24 and a positive potential is applied to it, while _H2UFB water is supplied to the cathode electrode 26 and a negative potential is applied to it compared to the other electrode.

In addition, the aging device 50 can also apply a potential difference similar to that of the voltage application unit 80 by using an electronic load unit (not shown) instead of the voltage application unit 80 and passing a current to either the anode or cathode side (or alternately).

In UFB aging (concentration cell), the control unit 54 may implement the first pattern or the second pattern alone, or may implement the first and second patterns alternately at predetermined intervals. Below, we will explain the action of the fuel cell 10 by supplying UFB water in the first and second patterns.

In the first pattern, as shown in FIG. 4, the aging device 50 supplies H ₂ UFB to the anode flow path 30 and the anode electrode 24 through the first circulating portion 60, and supplies N ₂ UFB to the cathode flow path 32 and _the cathode electrode 26 through the second circulating portion 70. As a result, the MEA 18 has a high H ₂ concentration on the anode electrode 24 side and a low H ₂ concentration on the cathode electrode 26 side. Therefore, in the MEA 18, a movement of protons flowing from the anode electrode 24 to the cathode electrode 26 through the electrolyte membrane 22 is created so that the H 2 concentration difference is balanced. Also, as described above, since the surface potential of the H ₂ UFB is negatively charged, the H ₂ UFB in the anode electrode 24 can be promoted to move toward the cathode electrode 26 side to which a positive voltage is applied by the power supply from the voltage application portion 80 to the terminal plates 44a, 44b.

At this time, the H ₂ UFB supplied to the anode flow path 30 has a bubble diameter smaller than the average pore diameter of the gas diffusion layer 24c and the dense carbon layer 24b. Therefore, the H ₂ UFB moves in the gas diffusion layer 24c and the dense carbon layer 24b without breaking the bubbles. In the catalyst layer 24a, the average pore diameter is smaller than the bubble diameter of the H ₂ UFB, so that the H ₂ UFB easily bursts and becomes H ₂ molecules. That is, UFB aging can sufficiently distribute both H ₂ molecules and water molecules (H ₂ O) in the catalyst layer 24a.

The _H2 that has moved to the catalyst layer 24a reacts with the platinum catalyst and is ionized into protons (H ⁺ ) and electrons ( ^e- ). The ionized protons move from the anode side to the cathode side within the MEA 18 together with the electroosmotic water. Meanwhile, the electrons move to the first separator 20a in contact with the anode electrode 24, and then move to the second separator 20b via the harness 56 and the voltage application unit 80.

On the other hand, the N ₂ UFB supplied to the cathode electrode 26 is dispersed in the gas diffusion layer 26c, the dense carbon layer 26b, and the catalyst layer 26a. This N ₂ UFB does not react with the platinum catalyst, thereby suppressing unnecessary reactions (reactions with oxygen, protons, and electrons) in the catalyst layer 26a. As a result, the protons that have moved through the MEA 18 and the electrons of the cathode electrode 26 react with the platinum catalyst in the catalyst layer 26a to become H ₂ molecules. The H ₂ molecules generated at the cathode electrode 26 are discharged from the fuel cell 10 together with the N ₂ UFB water.

In addition, the aging device 50 may control the pressure on the anode electrode 24 side to be higher than the pressure on the cathode electrode 26 side when the first pattern is implemented. Specifically, the control unit 54 reduces the opening of the first valve 67 to be smaller than the opening of the second valve 77, and increases the water supply amount of the first water supply unit 68 and the rotation speed of the first pump 66 to be higher than the water supply amount of the second water supply unit 78 and the rotation speed of the second pump 76. This allows the aging device 50 to make the water pressure in the first circulation path 61 and the fuel cell stack 12 (anode flow path 30) higher than the water pressure in the second circulation path 71 and the fuel cell stack 12 (cathode flow path 32).

For example, the aging device 50 increases the pressure (differential pressure) on the anode electrode 24 side by about 50 kPa to 150 kPa relative to the pressure on the cathode electrode 26 side. In this way, by increasing the pressure on the side supplying H ₂ UFB, the H ₂ UFB in the H ₂ UFB water supplied to the anode electrode 24 side can move more easily to the catalyst layer 24a, making it possible to efficiently generate protons in the catalyst layer 24a.

5, the aging device 50 supplies _N2 UFB water to the anode flow path 30 and the anode electrode 24 through the first circulating part 60, while supplying _H2 UFB water to the cathode flow path 32 and the cathode electrode 26 through the second circulating part 70. This creates a flow of protons from the cathode electrode 26 to the anode electrode 24 through the electrolyte membrane 22 in the MEA 18 so that the _H2 concentration difference is balanced.

At this time, the H ₂ UFB supplied to the cathode flow path 32 moves to the catalyst layer 26a through the gas diffusion layer 26c and the dense carbon layer 26b, and is ruptured at the catalyst layer 26a, so that the H ₂ molecules are easily diffused into the catalyst layer 26a. The H ₂ molecules in the catalyst layer 26a react with the platinum catalyst and are ionized into protons (H ⁺ ) and electrons (e ^- ). The ionized protons move from the cathode side to the anode side in the MEA 18 together with the electroosmotic water. Meanwhile, the electrons move to the second separator 20b in contact with the cathode electrode 26, and move to the first separator 20a via the harness 56 and the voltage application unit 80.

As a result, in the anode electrode 24, the protons that have migrated through the MEA 18 and the electrons of the anode electrode 24 react with the platinum catalyst of the catalyst layer 24a to become _H2 molecules. The _H2 molecules generated in the anode electrode 24 are discharged together with the _N2 UFB water.

Also, when implementing the second pattern, the aging device 50 may control the pressure on the cathode electrode 26 side to be higher than the pressure on the anode electrode 24 side. That is, the control unit 54 makes the opening of the second valve 77 smaller than the opening of the first valve 67, and increases the water supply amount of the second water supply unit 78 and the rotation speed of the second pump 76 higher than the water supply amount of the first water supply unit 68 and the rotation speed of the first pump 66. As a result, the aging device 50 can efficiently direct protons from the catalyst layer 26a of the cathode electrode 26 to the electrolyte membrane 22 by sufficiently increasing the pressure (differential pressure) on the cathode electrode 26 side relative to the pressure on the anode electrode 24 side.

When the control unit 54 alternately performs the first pattern and the second pattern and performs control to apply a pressure difference between the pair of electrodes, it is preferable to perform a conditioning process when switching between the first pattern and the second pattern in order to prevent overload of the electrolyte membrane 22. In this conditioning process, a purge control is performed to discharge H ₂ UFB water from the circulation path on the supply side of the high-pressure H ₂ UFB water in order to reduce (or make zero) the pressure difference between the pair of electrodes.

In addition, _H2 molecules tend to remain in the electrode to which _H2 UFB water was supplied. For this reason, when switching between the first and second patterns, it is preferable to perform _N2 supply control to supply _N2 UFB water to the electrode that was previously supplied with _H2 UFB water as a conditioning step.

For example, in the conditioning step, the control unit 54 can efficiently eliminate the pressure difference and remove the remaining hydrogen from the electrodes by simultaneously carrying out the purge control and the N ₂ supply control.

The aging device 50 according to this embodiment is basically configured as described above, and the aging method for the fuel cell 10 will be described below with reference to Fig. 6A. Specifically, the aging method for the fuel cell 10 sequentially performs UFB aging (step S1), _N2 purging (step S2), CV aging (step S3), and performance evaluation (step S4).

The UFB aging in step S1 is a process for facilitating the movement of protons by mainly increasing the wetness of the electrolyte membrane 22. In this UFB aging, the aging device 50 described above is used to supply UFB water (H ₂ UFB, N ₂ UFB) to the manufactured fuel cell stack 12. This improves gas diffusion in the anode electrode 24 and the cathode electrode 26, making it possible to efficiently increase the wetness of the electrolyte membrane 22.

For example, in UFB aging, the aging device 50 alternates between the first pattern (supply application pattern) and the second pattern (reverse supply application pattern). In this case, as shown in FIG. 6B, the control unit 54 repeats the following steps until UFB aging is completed: implementation of the first pattern (step S1-1), determination of the end of the first pattern (step S1-2), conditioning process (step S1-3), implementation of the second pattern (step S1-4), determination of the end of the second pattern (step S1-5), and conditioning process (step S1-6).

In carrying out the first pattern, the control unit 54 controls the first pump 66 and the first water supply unit 68 of the first circulation unit 60, and the second pump 76 and the second water supply unit 78 of the second circulation unit 70 to circulate water to the anode electrode 24 and the cathode electrode 26. The control unit 54 controls the first UFB generation unit 62 to supply H ₂ from the H ₂ gas source 64 to generate H ₂ UFB in the mixing unit 63, and controls the second UFB generation unit 72 to supply N ₂ from the N ₂ gas source 75 to generate N ₂ UFB in the mixing unit 73. As a result, the aging device 50 supplies H ₂ UFB water to the anode electrode 24, and supplies N ₂ UFB water to the cathode electrode 26.

At this time, the control unit 54 controls the first pump 66, the first water supply unit 68, and the first valve 67 of the first circulation unit 60 to make the pressure on the anode electrode 24 side, which supplies the H ₂ UFB water, higher than the pressure on the cathode electrode 26 side, which supplies the N ₂ UFB water. This allows a large amount of H ₂ UFB to move smoothly to the catalyst layer 24a of the anode electrode 24. Furthermore, the control unit 54 may stop the circulation of the H ₂ UFB water by stopping the first pump 66 and closing the first valve 67 when the pressure on the anode electrode 24 side increases. This stopping ensures that the H ₂ UFB water is retained at the anode electrode 24.

Then, while the H ₂ UFB water is being supplied to the anode electrode 24, the control unit 54 applies a negative potential to the anode electrode 24 and a positive potential to the cathode electrode 26 by the voltage application unit 80 compared to the other electrodes. By the above control, as shown in FIG. 4, a large amount of H ₂ UFB is exploded and becomes H ₂ molecules in the catalyst layer 24a of the anode electrode 24 of the MEA 18. Then, the H ₂ molecules react with the platinum catalyst and are ionized into protons and electrons, and these protons move to the cathode electrode 26 by passing through the electrolyte membrane 22 together with the electro-osmotic water. In the catalyst layer 26a of the cathode electrode 26, the protons and electrons that have moved through the electrolyte membrane 22 react with the platinum catalyst and become H ₂ molecules.

During the implementation of the first pattern, the control unit 54 judges whether the supply of H ₂ UFB water to the anode electrode 24 has been performed for a predetermined supply period (including the period during which circulation is stopped), and if the supply period has not elapsed, the control unit 54 maintains the use of the same H ₂ UFB water. That is, the control unit 54 continuously circulates the H ₂ UFB water between the fuel cell stack 12 and the first circulation path 61. Conversely, if the predetermined supply period has elapsed, the control unit 54 drains the H ₂ UFB water from the first circulation path 61 and supplies new H ₂ UFB water to the first circulation path 61. As a result, the aging device 50 fully reuses the H ₂ UFB water generated by the first UFB generation unit 62 before discharging it from the first circulation path 61, thereby reducing H ₂ consumption.

Returning to FIG. 6B, the control unit 54 judges whether the first pattern has been performed for a predetermined period (step S1-2), and if it has not been performed for a predetermined period (step S1-2: NO), the control unit 54 continues the first pattern, whereas if it has been performed for a predetermined period (step S1-2: YES), the control unit 54 proceeds to the conditioning step (step S1-3). In the conditioning step, the control unit 54 fully opens the first valve 67 and opens the first discharge valve 69a of the first discharge path 69 to discharge the H ₂ UFB on the anode electrode 24 side. On the other hand, the second discharge valve 79a on the cathode electrode 26 side is not opened to maintain circulation in the second circulation path 71 (or circulation is stopped due to the blockage of the second valve 77). This reduces the water pressure of the H ₂ UFB water on the anode electrode 24 side, and reduces the pressure difference with the cathode electrode 26 side.

Furthermore, the control unit 54 operates the first UFB generation unit 62 and the first pump 66 of the first circulation unit 60 to supply _N2UFB water to the anode electrode 24 side while discharging _{H2UFB water from the first circulation path 61. This supply of N2UFB water} maintains the wetness of the electrolyte membrane 22 and the catalyst layer 24a while discharging _H2 molecules remaining in the anode electrode 24. Then, the control unit 54 ends the conditioning process after carrying out the above conditioning process for a set period of time (or until the pressure difference between the anode electrode 24 and the cathode electrode 26 becomes equal to or lower than a predetermined pressure).

Thereafter, the control unit 54 executes the second pattern (step S1-4). In executing the second pattern, the control unit 54 controls the first UFB generating unit 62 to supply N ₂ from the N ₂ gas source 65 to generate N ₂ UFB in the mixing unit 63, and controls the second UFB generating unit 72 to supply H ₂ from the H ₂ gas source 74 to generate H ₂ UFB in the mixing unit 73. As a result, the aging device 50 supplies N ₂ UFB water to the anode electrode 24, and supplies H ₂ UFB water to the cathode electrode 26. At this time, the control unit 54 makes the pressure on the cathode electrode 26 side where the H ₂ UFB water is supplied higher than the pressure on the anode electrode 24 side where the N ₂ UFB water is supplied. In addition, the control unit 54 may stop the circulation of the H ₂ UFB water by stopping the second pump 76 and closing the second valve 77 at the stage where the pressure on the cathode electrode 26 side has increased. This shutdown ensures that the high pressure H ₂ UFB water remains at the cathode electrode 26 .

Furthermore, while _H2 UFB water is being supplied to the cathode electrode 26, the control unit 54 causes the voltage application unit 80 to apply a negative potential to the cathode electrode 26 compared to the other electrode, and a positive potential to the anode electrode 24. Through the above control, as shown in Fig. 5, a large amount of protons that have reacted with the platinum catalyst at the cathode electrode 26 pass through the electrolyte membrane 22 together with electroosmotic water. Then, at the anode electrode 24, the protons and electrons react with the platinum catalyst to become _H2 molecules.

Also, during the second pattern, the control unit 54 determines whether the supply of _H2UFB water to the cathode electrode 26 has been performed for a predetermined supply period (including the period when circulation is stopped), and if the supply period has not elapsed, continues to use the _H2UFB water. Conversely, if the predetermined supply period has elapsed, drains the _H2UFB water from the second circulation path 71 and supplies new _H2UFB water to the second circulation path 71.

Returning to FIG. 6B, the control unit 54 determines whether the second pattern has been performed for a predetermined period of time (step S1-5), and if it has not been performed for the predetermined period of time (step S1-5: NO), the control unit 54 continues the second pattern, whereas if it has been performed for the predetermined period of time (step S1-5: YES), the control unit 54 performs a conditioning step (step S1-6). In this conditioning step, the control is reversed from that of the conditioning step in step S1-3.

That is, the control unit 54 discharges H ₂ UFB on the cathode electrode 26 side to reduce the water pressure of the H ₂ UFB water on the cathode electrode 26 side, thereby reducing the pressure difference with the cathode electrode 26 side. The control unit 54 also supplies N ₂ UFB water to the cathode electrode 26 side while discharging H ₂ UFB water from the second circulation path 71. This supply of N ₂ UFB water makes it possible to discharge H ₂ molecules remaining in the cathode electrode 26 while maintaining the wetness of the electrolyte membrane 22 and the catalyst layer 26a. Then, the control unit 54 ends the conditioning process after carrying out the above conditioning process for a set period (or until the pressure difference between the cathode electrode 26 and the anode electrode 24 becomes equal to or less than a predetermined pressure).

The aging device 50 continues the above process flow for a set number of repetitions or for a set period of time to complete the UFB aging. After the UFB aging is completed, the aging method for the fuel cell 10 performs the next _N2 purge (step S2 in FIG. 6A). This _N2 purge process may be performed using the aging device 50 used in the UFB aging, or a different device may be used.

The _N2 purge is a process for discharging water, hydrogen, and the like remaining in the fuel cell stack 12 by supplying _N2 gas, which is an inert gas, to the anode flow path 30 and the cathode flow path 32 of the fuel cell stack 12 after UFB aging. For example, when the same aging device 50 is used, after discharging water from the first circulation path 61 and the second circulation path 71, _N2 gas is supplied from the _N2 gas source 65 of the first UFB generation unit 62 to the first circulation path 61, and _N2 gas is supplied from the _N2 gas source 75 of the second UFB generation unit 72 to the second circulation path 71. As a result, the humidity of the electrolyte membrane 22 of the fuel cell stack 12 is adjusted, and flooding of the anode electrode 24 and the cathode electrode 26 is prevented. It is of course possible to apply an inert gas other than _N2 gas in the _N2 purge. In addition, the aging device 50 may supply overhumidified _N2 gas obtained by overhumidifying _N2 gas in the _N2 purge.

Next, in the CV aging (voltage fluctuation aging) of step S3, a fluctuating voltage is applied to the fuel cell stack 12 after _N2 purging by using the aging device 50 used in the UFB aging described above, or by using a CV aging device not shown. This CV aging removes the oxidized film on the surface of the catalyst, and removes organic contaminants adhering to the catalyst, and increases the effective catalyst area of the MEA 18. As a result, the reactions _H2 → 2H ⁺ + ^e- and _O2 + 4H ⁺ + ^4e- → ^2H2O during power generation of the fuel cell 10 are promoted. In addition, since UFB aging has been performed first, protons move easily in the electrolyte membrane 22 during CV aging. Therefore, it is possible to shorten the time required for CV aging.

Finally, in the performance evaluation of step S4, the power generation performance of the fuel cell stack 12 (fuel cell 10) after CV aging is analyzed using an appropriate evaluation method. For example, the evaluation method detects the cell voltage and current during power generation by performing a power generation process on the fuel cell stack 12. Here, the fuel cell stack 12 that has undergone UFB aging and CV aging has a reduced concentration overvoltage in the IV curve as well as a reduced activation overvoltage. Therefore, the power generation performance of the fuel cell stack 12 is significantly improved.

As described above, the aging method for the fuel cell 10 improves the mobility (diffusibility) and wettability of _H2 molecules in the anode electrode 24 and the cathode electrode 26 by supplying UFB water ( _H2 UFB water, _N2 UFB water) in UFB aging (concentration cell). In other words, by carrying out UFB aging, the diffusion coefficient of protons in the MEA 18 increases, and accordingly the amount of electroosmotic water increases when protons move through the electrolyte membrane 22. Therefore, the water content of the MEA 18 (electrolyte membrane 22) can be efficiently increased.

The present invention is not limited to the above-described embodiment, and various modifications are possible in accordance with the gist of the invention. For example, the aging device 50 is not limited to UFB aging a fuel cell stack 12 having a plurality of fuel cells 10, and may be configured to UFB age a fuel cell 10, which is a unit power generation cell, by making appropriate modifications. Also, for example, the aging method of the fuel cell 10 may omit CV aging (step S3) if the power generation performance of the fuel cell 10 is sufficiently improved by implementing UFB aging.

Furthermore, the supply of UFB is not limited to when UFB aging is performed on the fuel cell 10, but can also be applied during power generation of the fuel cell stack 12 (fuel cell 10). For example, a fuel cell system (not shown) having the fuel cell stack 12 or an aging device 50 supplies H ₂ UFB water containing H ₂ UFB to the anode electrode 24, while supplying O ₂ UFB water containing UFB of O ₂ molecules to the cathode electrode 26. This allows each of the H ₂ molecules and the O ₂ molecules to be efficiently transferred to each catalyst layer of the MEA 18, and the fuel cell stack 12 can output sufficient power generation. In addition, in the above embodiment, the aging device 50 is provided with H ₂ gas sources 64, 74 and N ₂ gas sources 65, 75 in each of the first UFB generating unit 62 and the second UFB generating unit 72, but is not limited thereto, and may be configured to share the H ₂ gas sources 64, 74 and the N ₂ gas sources 65, 75. Hereinafter, a configuration for supplying O ₂ UFB water and a modified example in which the H ₂ gas sources 64, 74 and the N ₂ gas sources 65, 75 are shared in the aging method will be described with reference to FIGS. 7, 8A and 8B.

The aging device 50A has a supply processing unit 90 that supplies selected fluids (H ₂ UFB water, N 2 UFB water, O 2 UFB water, humidified H ₂ gas, humidified N ₂ gas, humidified O ₂ gas) to the anode flow path 30 (anode electrode 24), the cathode flow path 32 (cathode electrode 26), and the coolant flow path 34 (see FIG _{. 2} ) of the fuel cell stack 12, and a discharge processing unit 92 that processes each fluid discharged from the fuel cell stack 12. The supply processing unit 90 includes a first supply processing unit 94 that supplies O ₂ (air in this modification) and N ₂ , a second supply processing unit 96 that supplies H ₂ , and a supply flow path switching unit 98 that switches the flow path of the fluid between the fuel cell stack 12 and the first supply processing unit 94 and the second supply processing unit 96. The discharge treatment unit 92 includes a first discharge treatment unit 100 that treats the discharge of O ₂ and N ₂ , a second discharge treatment unit 102 that treats the discharge of H ₂ , and a discharge flow path switching unit 104 that switches the flow path of the fluid between the fuel cell stack 12 and the first discharge treatment unit 100 and the second discharge treatment unit 102. A first circulation path 106 that circulates the fluid of the first discharge treatment unit 100 is connected between the first supply treatment unit 94 and the first discharge treatment unit 100. In addition, a second circulation path 108 that circulates the fluid of the second discharge treatment unit 102 is connected between the second supply treatment unit 96 and the second discharge treatment unit 102.

As shown in Fig. 8A, the first supply processing unit 94 includes an air source 110, an air UFB generating unit 112, an air UFB tank 114, a bubbler tank 116, an _N2 gas source 118, an _N2 UFB generating unit 120, and an _N2 UFB tank 122. A water supply unit 124 is connected to each of the air UFB generating unit 112, the bubbler tank 116, and the _N2 UFB generating unit 120. The air UFB generating unit 112 appropriately mixes air supplied from the air source 110 and water supplied from the water supply unit 124 to generate air UFB water. The air UFB tank 114 stores the generated air UFB water and also stores the air UFB water circulated from the first discharge processing unit 100. The N ₂ UFB generating unit 120 appropriately mixes the N ₂ gas supplied from the N ₂ gas source 118 with the water supplied from the water supply unit 124 to generate N ₂ UFB water. The N ₂ UFB tank 122 stores the generated N ₂ UFB water and stores the N ₂ UFB water circulated from the first discharge processing unit 100. The bubbler tank 116 is connected to the air source 110, the N ₂ gas source 118, and the water supply unit 124, and generates humidified air or humidified N ₂ gas by supplying air or N ₂ gas to the water stored in the tank to foam it. The bubbler tank 116 also controls the temperature and humidity of the gas by adjusting the temperature with a temperature adjustment unit (not shown).

The first supply processing unit 94 has valves 126a, 126b, 126c, and 126d for selectively supplying air from the air source 110 to the air UFB generating unit 112 and the bubbler tank 116, and selectively supplying _N2 gas from the _N2 gas source 118 to the _N2 UFB generating unit 120 and the bubbler tank 116. Furthermore, the first supply processing unit 94 has a pump 128a and a valve 130a between the air UFB tank 114 and the output terminal 94a of the first supply processing unit 94, a pump 128b and a valve 130b between the bubbler tank 116 and the output terminal 94a, and a pump 128c and a valve 130c between the _N2 UFB tank 122 and the output terminal 94a. Furthermore, the first supply processing unit 94 has a path for supplying _N2UFB water as a coolant to the fuel cell stack 12, and this path also has a pump 128d and a valve 130d. The first supply processing unit 94 configured as above can output _N2UFB water, _O2UFB water, humidified _N2 gas, and humidified _O2 gas from the output terminal 94a to the downstream supply flow path switching unit 98.

On the other hand, the second supply processing unit 96 includes an _H2 gas source 132, an _H2 UFB generating unit 134, an _H2 UFB tank 136, and an _H2 bubbler tank 138, as shown in Fig. 8B. The water supply unit 124 is connected to each of the _H2 UFB generating unit 134 and the _H2 bubbler tank 138. The _H2 UFB generating unit 134 appropriately mixes the _H2 gas supplied from the _H2 gas source 132 with the water supplied from the water supply unit 124 to generate _H2 UFB water. The _H2 UFB tank 136 stores the generated _H2 UFB water and also stores the _H2 UFB water circulated from the second exhaust processing unit 102. The _H2 bubbler tank 138 is connected to the _H2 gas source 132 and the water supply unit 124, and generates humidified _H2 gas by supplying _H2 gas to the water stored in the tank and bubbling it. The _H2 bubbler tank 138 also controls the temperature and humidity of the gas by adjusting the temperature with a temperature adjustment unit (not shown).

The second supply processing unit 96 has valves 140a and 140b for selectively supplying _H2 gas from the _H2 gas source 132 to the _H2 UFB generating unit 134 and the _H2 bubbler tank 138, and further has a pump 142a and a valve 144a between the _H2 UFB tank 136 and the output terminal 96a of the second supply processing unit 96, and has a pump 142b and a valve 144b between the _H2 bubbler tank 138 and the output terminal 96a. The second supply processing unit 96 configured as above can output _H2 UFB water and humidified _H2 gas from the output terminal 96a to the downstream supply flow path switching unit 98.

Returning to FIG. 7, the supply flow path switching unit 98 is provided with a plurality of pipes 150 between the first supply processing unit 94 and the fuel cell stack 12, and between the second supply processing unit 96 and the fuel cell stack 12. Each of the plurality of pipes 150 is provided with a plurality of valves 152 (valves 152a, 152b, 152c, 152d). The supply flow path switching unit 98 configured in this manner supplies the fluid of the first supply processing unit 94 to one of the anode electrode 24 and the cathode electrode 26, while supplying the fluid of the second supply processing unit 96 to the other of the anode electrode 24 and the cathode electrode 26, under switching of the plurality of valves 152.

Similarly, the discharge flow path switching unit 104 includes a plurality of pipes 160 between the first discharge processing unit 100 and the fuel cell stack 12, and between the second discharge processing unit 102 and the fuel cell stack 12. Each of the plurality of pipes 160 is provided with a plurality of valves 162 (valves 162a, 162b, 162c, 162d). The discharge flow path switching unit 104 thus configured discharges fluid from one of the anode electrode 24 and the cathode electrode 26 to the first discharge processing unit 100 under switching of the plurality of valves 162, while discharging fluid from the other of the anode electrode 24 and the cathode electrode 26 to the second discharge processing unit 102.

The first discharge processing unit 100 has a first recovery tank 170 that recovers N ₂ UFB water, O ₂ UFB water, N ₂ gas, and O ₂ gas. The first circulation path 106 is connected between the input terminal 100a of the first discharge processing unit 100 and the first recovery tank 170. A valve 172a is provided between the input terminal 100a and the first recovery tank 170, and a valve 172b is also provided on the first circulation path 106. The first discharge processing unit 100 configured in this manner can discharge N ₂ UFB water, O ₂ UFB water, N ₂ gas, and O ₂ gas into the first recovery tank 170 and circulate them through the first circulation path 106 under switching of the valves 172a and 172b.

Similarly, the second discharge processing unit 102 has a second recovery tank 174 that recovers H ₂ UFB water and H ₂ gas. In addition, the second circulation path 108 is connected between the input terminal 102a of the second discharge processing unit 102 and the second recovery tank 174. A valve 176a is provided between the input terminal 102a and the second recovery tank 174, and a valve 176b is also provided on the second circulation path 108. The second discharge processing unit 102 configured in this manner can discharge H ₂ UFB water and H ₂ gas into the second recovery tank 174 and circulate them through the second circulation path 108 under switching of the valves 176a and 176b.

The aging device 50A configured as above can implement the above-mentioned first pattern by supplying H ₂ UFB water to the anode electrode 24 while supplying N ₂ UFB water to the cathode electrode 26 and applying a potential by the voltage application unit 80 (see FIG. 1). Furthermore, the aging device 50A can implement the second pattern by supplying H ₂ UFB water to the anode electrode 24 while supplying H ₂ UFB water to the cathode electrode 26 and applying a potential by the voltage application unit 80. Even in the conditioning step between the first pattern and the second pattern, the above-mentioned purge control and N ₂ supply control can be performed by appropriately switching the pipes 150, 160 by the supply flow path switching unit 98 and the exhaust flow path switching unit 104. In particular, the first supply processing unit 94 can easily supply humidified N ₂ gas to the fuel cell stack 12 in the N ₂ supply control.

Furthermore, the aging device 50A can generate power in the fuel cell stack 12 by supplying H ₂ UFB water to the anode electrode 24 and O ₂ UFB water to the cathode electrode 26. Alternatively, during aging, the aging device 50A can generate power in the fuel cell stack 12 by supplying O ₂ UFB water to the anode electrode 24 and H ₂ UFB water to the cathode electrode 26. Power generation in the fuel cell stack 12 may be performed by combining the first pattern and the second pattern during UFB aging, or may be performed after UFB aging.

In another modification, the separators (first separator 20a, second separator 20b) constituting the fuel cell 10 may have a seal portion (not shown) between adjacent separators to prevent leakage of gas and liquid from the flow path to the outside. In this case, when forming the seal portion of the separator, there is a risk that water-repellent substances such as siloxane will scatter and adhere to the surface facing the power generation unit. Therefore, it is preferable to wash the separator with UFB water during the manufacture of the separator (before or during the UFB aging process). This allows the UFB water to enter the minute gaps in the separator, thereby removing the water-repellent substances that adhered during the manufacture. In addition, the hydrophilicity of the surface of the separator can be increased by washing with UFB water, and by constructing the fuel cell 10 with this separator, it is expected that the aging time of the fuel cell 10 will be shortened or the variation in cell voltage will be improved.

Second Embodiment
The aging method for the fuel cell 10 according to the second embodiment utilizes the principle of a hydrogen pump to pass protons (H ⁺ ) through the MEA 18 during UFB aging. In a hydrogen pump, a flow of electrons is created by a DC power supply connected to the fuel cell 10, and protons are moved in the direction where there are more electrons in the MEA 18. In other words, this is a method of moving (pumping) protons by electric current.

However, the same device as the aging device 50 according to the first embodiment can be applied to UFB aging that utilizes the principle of this hydrogen pump. Specifically, in UFB aging (hydrogen pump), the control unit 54 of the aging device 50 controls the operation of the first circulating unit 60, the second circulating unit 70, and the voltage application unit 80 to implement two patterns, as shown in Figures 9A and 9B.

The first pattern shown in Fig. 9A is a supply application pattern in which _H2UFB water is supplied to the anode electrode 24 and a positive potential is applied, while _N2UFB water is supplied to the cathode electrode 26 and a negative potential is applied compared to the other electrode. The second pattern shown in Fig. 9B is a reverse supply application pattern in which _N2UFB water is supplied to the anode electrode 24 and a negative potential is applied compared to the other electrode, while _H2UFB water is supplied to the cathode electrode 26 and a positive potential is applied. Note that even with this hydrogen pump principle, the control unit 54 can independently perform the first pattern or the second pattern, or can alternately perform the first pattern and the second pattern at predetermined intervals.

Incidentally, even in the aging method using a hydrogen pump, the aging device 50 can use an electronic load unit (not shown) instead of the voltage application unit 80 to pass a current to either the anode or cathode side (or alternately), thereby applying a potential difference similar to that of the voltage application unit 80.

In the first pattern, as shown in FIG. 10, the aging device 50 supplies H ₂ UFB water to the anode flow path 30 and the anode electrode 24 through the first circulating part 60, and supplies N ₂ UFB water to the cathode flow path 32 and the cathode electrode 26 through the second circulating part 70. H ₂ UFB moves to the catalyst layer 24a through the gas diffusion layer 24c and the dense carbon layer 24b by the water pressure (water flow) of the H ₂ UFB water at the anode electrode 24, and becomes H ₂ molecules by bursting at the catalyst layer 24a. In particular, the control unit 54 controls the pressure on the anode electrode 24 side to be higher than the pressure on the cathode electrode 26 side, which makes it easier for H ₂ UFB to move toward the catalyst layer 24a. Then, the H ₂ molecules react with the platinum catalyst and are ionized into protons (H ⁺ ) and electrons (e ^- ).

Furthermore, the voltage application unit 80 applies a positive potential to the anode electrode 24 and a negative potential to the cathode electrode 26 compared to the other electrode. As a result, the ionized electrons move to the first separator 20a of the anode electrode 24, and then move to the second separator 20b of the cathode electrode 26 via the harness 56 and the voltage application unit 80. In other words, the cathode electrode 26 attracts protons due to the movement of many electrons. Therefore, the protons in the catalyst layer 24a of the anode electrode 24 move inside the MEA 18 together with the electroosmotic water. The protons and electrons that have moved to the catalyst layer 26a of the cathode electrode 26 react with the platinum catalyst to become _H2 molecules, and these _H2 molecules are discharged from the fuel cell 10 together with the _N2 UFB water.

9B , in the second pattern, the aging device 50 reverses the electrodes to which UFB water (H ₂ UFB water, N ₂ UFB water) is supplied from the first pattern, and also reverses the electrodes to which voltage is applied from the first pattern. This allows the fuel cell 10 to move protons from the cathode electrode 26 to the anode electrode 24 via the electrolyte membrane 22, in the opposite manner to the above, and to humidify the cathode electrode 26 with electroosmotic water (a detailed description of the operation of the fuel cell 10 will be omitted).

As described above, the aging method of the fuel cell 10 can achieve the same effect as the first embodiment even with UFB aging using the principle of the hydrogen pump. That is, this aging method can efficiently increase the water content of the MEA 18 (electrolyte membrane 22) by increasing the diffusion coefficient of protons in the MEA 18 and increasing the amount of electroosmotic water associated with proton movement. In particular, UFB aging using the principle of the hydrogen pump can further increase the efficiency of proton movement by transferring electrons by applying a DC voltage.

Third Embodiment
The aging method for the fuel cell 10 according to the third embodiment differs from the aging methods for the fuel cell 10 according to the first and second embodiments in that CV aging is performed simultaneously when UFB aging is performed, as shown in Fig. 11. Note that the aging device 50 that performs UFB aging can be the same as the aging device 50 used in the first and second embodiments.

Specifically, the aging method sequentially performs UFB+CV aging (step S11), _N2 purging (step S12), CV aging (step S13), and performance evaluation (step S14). In UFB+CV aging, the control unit 54 performs UFB aging using the principle of a concentration cell or hydrogen pump, while varying the voltage applied to the anode electrode 24 and the cathode electrode 26 by the voltage application unit 80. As a result, the fuel cell 10 that has undergone UFB+CV aging has an increased water content in the electrolyte membrane 22 and an improved catalyst effective area.

Therefore, the aging method can further shorten the time required for CV aging (step S13) after _N2 purging (step S12). And, even if UFB+CV aging is performed in this way and the CV aging time is shortened, the power generation performance of the fuel cell stack 12 can be significantly improved. It goes without saying that, even in the aging method for the fuel cell 10 according to the third embodiment, CV aging may be omitted if the power generation performance of the fuel cell 10 is sufficiently improved by performing UFB+CV aging.

The technical ideas and effects that can be understood from the above embodiments are described below.

One aspect of the present invention is a method for aging a fuel cell 10 having an electrolyte membrane 22 and a pair of electrodes (anode electrode 24, cathode electrode 26) provided on both sides of the electrolyte membrane 22, in which hydrogen ultra-fine bubble water ( _H2 UFB water) containing hydrogen that can be separated into protons as ultra-fine bubbles (UFB) is supplied to one electrode of the fuel cell 10, and ultra-fine bubble aging is performed in which protons are transferred from one electrode to the other electrode through the electrolyte membrane 22.

As described above, the aging method for the fuel cell 10 can effectively transfer the H ₂ UFB water supplied to the fuel cell 10 to the catalyst layer 24a (or catalyst layer 26a) of one electrode. As a result, protons ionized from hydrogen in the catalyst layer 24a (or catalyst layer 26a) can move through the electrolyte membrane 22 together with electroosmotic water, thereby further promoting humidification of the electrolyte membrane 22. In other words, ultra-fine bubble aging using H ₂ UFB water can improve the efficiency of aging of the fuel cell 10.

In addition, after ultra-fine bubble aging is performed, voltage fluctuation aging (CV aging) is performed in which a voltage that fluctuates within a predetermined voltage range is applied to a pair of electrodes (anode electrode 24, cathode electrode 26). This allows the aging method of the fuel cell 10 to perform CV aging on the fuel cell 10 whose gas diffusivity has been increased by humidifying the electrolyte membrane 22, and this CV aging makes it possible to secure the effective catalyst area in a short period of time.

In ultra-fine bubble aging, a supply and application pattern is used in which hydrogen ultra-fine bubble water is supplied to the anode electrode 24, which is one of a pair of electrodes, and a negative potential is applied to the other electrode, while nitrogen ultra-fine bubble water containing nitrogen as ultra-fine bubbles is supplied to the cathode electrode 26, which is one of a pair of electrodes, and a positive potential is applied. This makes it possible for the aging method for the fuel cell 10 to move protons between the electrodes by utilizing the principle of a concentration cell, and enables good UFB aging.

In addition, in ultra-fine bubble aging, a supply application pattern and a reverse supply application pattern are alternated, in which nitrogen ultra-fine bubble water is supplied to the anode electrode 24 and a positive potential is applied, while hydrogen ultra-fine bubble water is supplied to the cathode electrode 26 and a negative potential is applied compared to the other electrode. This allows the aging method of the fuel cell 10 to humidify the electrolyte membrane 22 from both the anode electrode 24 and the cathode electrode 26, further improving the efficiency of UFB aging.

In addition, electricity is generated by supplying hydrogen ultra-fine bubble water to the anode electrode 24, which is a pair of electrodes, and oxygen ultra-fine bubble water, which contains oxygen as ultra-fine bubbles, to the cathode electrode 26, which is also a pair of electrodes. By supplying this hydrogen ultra-fine bubble water and oxygen ultra-fine bubble water, the fuel cell 10 is able to efficiently supply hydrogen and oxygen to the catalyst layers 24a, 26a, enabling good electricity generation.

In addition, a supply and application pattern is used in which hydrogen ultra-fine bubble water is supplied to the anode electrode 24, which is one of a pair of electrodes, and a positive potential is applied, and nitrogen ultra-fine bubble water containing nitrogen as ultra-fine bubbles is supplied to the cathode electrode 26, which is one of a pair of electrodes, and a negative potential is applied to the other electrode. Even in this case, the aging method for the fuel cell 10 makes it possible to move protons between the electrodes by utilizing the principle of a hydrogen pump, and UFB aging can be performed well.

In addition, in ultra-fine bubble aging, a supply application pattern and a reverse supply application pattern are alternated, in which nitrogen ultra-fine bubble water is supplied to the anode electrode 24 while a negative potential is applied compared to the other electrode, and hydrogen ultra-fine bubble water is supplied to the cathode electrode 26 while a positive potential is applied. Even when using the principle of a hydrogen pump in this way, the electrolyte membrane 22 can be humidified from both the anode electrode 24 and the cathode electrode 26, further improving the efficiency of UFB aging.

In addition, the pressure on the side supplying ultra-fine hydrogen bubble water is set higher than the pressure on the side supplying ultra-fine nitrogen bubble water, which allows the UFB aging process to more efficiently transfer _H2UFB to the catalyst layers 24a and 26a in the electrodes.

In addition, at the end of the supply application pattern or reverse supply application pattern, the pressure on the side supplying hydrogen ultra-fine bubble water is lowered, thereby lowering the pressure difference with the side supplying nitrogen ultra-fine bubble water. This makes it possible for the aging method of the fuel cell 10 to suppress overloading of the electrolyte membrane 22 caused by a sudden change in pressure at the end of the supply application pattern or reverse supply application pattern.

In addition, at the end of the supply application pattern or the reverse supply application pattern, nitrogen is supplied to the electrode supplying the hydrogen ultra-fine bubble water to discharge the remaining hydrogen. This makes it possible for the aging method of the fuel cell 10 to easily discharge the hydrogen remaining in the electrode.

In addition, when ultra-fine bubble aging is performed, the applied voltage is varied within a predetermined voltage range. This allows the aging method of the fuel cell 10 to combine UFB aging with CV aging, further shortening the aging time.

In addition, after circulating the ultra-fine hydrogen bubble water around one of the electrodes for a specified supply period, the ultra-fine hydrogen bubble water is discharged. This makes it possible for the aging method for the fuel cell 10 to fully use up the ultra-fine hydrogen bubbles, thereby suppressing hydrogen consumption.

In addition, after a predetermined amount of ultra-fine hydrogen bubble water is supplied to one of the electrodes, the supply of ultra-fine hydrogen bubble water is stopped. This aging method for the fuel cell 10 can suppress _H2 consumption.

In addition, the fuel cell 10 has a pair of separators (first separator 20a, second separator 20b) installed on each of the electrode surfaces of the pair of electrodes, and the separators are washed with ultra-fine bubble water before or during the ultra-fine bubble aging process. This makes it possible to increase the hydrophilicity of the separator surface, and by configuring the fuel cell 10 with this separator, it is expected that the aging time of the fuel cell 10 can be shortened or the variation in cell voltage can be improved.

Claims (11)

A method for aging a fuel cell (10) having an electrolyte membrane (22) and a pair of electrodes (24, 26) provided on both sides of the electrolyte membrane, comprising the steps of:
supplying ultra-fine hydrogen bubble water, which contains hydrogen that can be separated into protons as ultra-fine bubbles, to one electrode of the fuel cell;
performing ultra-fine bubble aging to transfer the protons from the one electrode to the other electrode through the electrolyte membrane;
In the ultra-fine bubble aging,
a supply and application pattern in which the hydrogen ultra-fine bubble water is supplied to the anode electrode (24) of the pair of electrodes and a negative potential is applied to the other electrode, while nitrogen ultra-fine bubble water containing nitrogen as ultra-fine bubbles is supplied to the cathode electrode (26) of the pair of electrodes and a positive potential is applied;
The nitrogen ultra-fine bubble water is supplied to the anode electrode and a positive potential is applied to the anode electrode, while the hydrogen ultra-fine bubble water is supplied to the cathode electrode and a negative potential is applied to the cathode electrode compared to the other electrode. This reverse supply application pattern is performed alternately.
A method for aging a fuel cell. The method for aging a fuel cell according to claim 1,
After carrying out the ultra-fine bubble aging,
a voltage fluctuation aging process for applying a voltage that fluctuates within a predetermined voltage range to the pair of electrodes; The method for aging a fuel cell according to claim 1 or 2,
The ultra-fine hydrogen bubble water is supplied to the anode electrode,
The method for aging a fuel cell comprises supplying ultra-fine oxygen bubble water containing oxygen as ultra-fine bubbles to the cathode electrode to generate electricity. A method for aging a fuel cell having an electrolyte membrane and a pair of electrodes provided on both sides of the electrolyte membrane, comprising the steps of:
supplying ultra-fine hydrogen bubble water, which contains hydrogen that can be separated into protons as ultra-fine bubbles, to one electrode of the fuel cell;
performing ultra-fine bubble aging to transfer the protons from the one electrode to the other electrode through the electrolyte membrane;
The hydrogen ultra-fine bubble water is supplied to the anode electrodes, which are the pair of electrodes, and a positive potential is applied to the anode electrodes.
A supply and application pattern is performed in which ultra-fine nitrogen bubble water containing nitrogen as ultra-fine bubbles is supplied to the cathode electrode, which is one of the pair of electrodes, and a negative potential is applied to the cathode electrode compared to the other electrode.
In the ultra-fine bubble aging, the supply application pattern and
The ultra-fine nitrogen bubble water is supplied to the anode electrode, and a negative potential is applied to the anode electrode compared to the other electrode.
The method for aging a fuel cell comprises alternately supplying the ultra-fine hydrogen bubble water to the cathode electrode and applying a positive potential in a reverse supply application pattern. The method for aging a fuel cell according to claim 1 or 4 ,
a pressure on the side where the ultra-fine hydrogen bubble water is supplied is set higher than a pressure on the side where the ultra-fine nitrogen bubble water is supplied. The method for aging a fuel cell according to claim 5 ,
the pressure on the side supplying the ultra-fine hydrogen bubble water is lowered at the end of the supply application pattern or the reverse supply application pattern, thereby reducing the pressure difference with the pressure on the side supplying the ultra-fine nitrogen bubble water. The aging method for a fuel cell according to any one of claims 1 and 4 to 6 ,
and when the supply application pattern or the reverse supply application pattern is terminated, nitrogen is supplied to the electrode that supplies the ultra-fine hydrogen bubble water, thereby discharging remaining hydrogen. The method for aging a fuel cell according to any one of claims 1 to 7 ,
the method for aging a fuel cell further comprising fluctuating the applied voltage within a predetermined voltage range during the ultra-fine bubble aging process. The method for aging a fuel cell according to any one of claims 1 to 8 ,
the ultra-fine hydrogen bubble water is circulated around one of the electrodes for a predetermined period of time, and then the ultra-fine hydrogen bubble water is discharged. The method for aging a fuel cell according to any one of claims 1 to 9 ,
a predetermined amount of ultra-fine hydrogen bubble water is supplied to one of the electrodes, and then the supply of the ultra-fine hydrogen bubble water is stopped. The method for aging a fuel cell according to any one of claims 1 to 10 ,
The fuel cell has a pair of separators disposed on each of the electrode surfaces of the pair of electrodes,
the separator is washed with ultra-fine bubble water before or during the ultra-fine bubble aging treatment.

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