JP6973003B2 - Aging method for polymer electrolyte fuel cells - Google Patents

Description

The present invention relates to a method for aging a polymer electrolyte fuel cell having a membrane electrode assembly in which a pair of electrodes are arranged on both sides of an electrolyte membrane and a separator.

In a fuel cell, fuel gas (for example, hydrogen) and oxidant gas (for example, air), which are reaction gases, are used as an anode side electrode (hereinafter, may be simply referred to as an anode) and a cathode side electrode (hereinafter, may be simply referred to as a cathode). It is a system that obtains electrical energy (electromotive electrode) by supplying it to the fuel cell and causing it to react electrochemically.

For example, a cell of a solid polymer fuel cell (sometimes referred to as a fuel cell or a single cell) has an ion-permeable electrolyte membrane, an anode-side catalyst layer (electrode layer) and a cathode-side catalyst sandwiching the electrolyte membrane. A membrane electrode assembly (MEA) composed of a layer (electrode layer) is provided. Gas diffusion layers (GDL) are formed on both sides of the MEA to provide fuel gas or oxidant gas and to collect electricity generated by an electrochemical reaction. MEA in which GDL is arranged on both sides is called MEGA (Membrane Electrode & Gas Diffusion Layer Assembly), and MEGA is sandwiched by a pair of separators. Here, the MEGA is the power generation unit of the fuel cell, and when there is no gas diffusion layer, the MEA is the power generation unit of the fuel cell.

A fuel cell (sometimes referred to as a fuel cell stack) is used by stacking a plurality of cells having the above-mentioned configurations on top of each other and mounting them on a vehicle such as an automobile, for example.

In this type of polymer electrolyte fuel cell, the water content of the electrolyte membrane immediately after assembly is not sufficient (specifically, because the electrolyte membrane is dried and the proton conduction path is not sufficiently formed), so the initial power generation performance is poor. It's getting low. Therefore, in order to bring out the desired power generation performance after assembling the fuel cell, a preliminary operation (break-in operation) called an aging operation (simply also referred to as aging) of the fuel cell is usually performed. This aging operation is such that the performance of the cell can exhibit the desired ability by preliminarily generating power after assembling the fuel cell. In addition, not only after manufacturing, but also when regenerating power (at the time of restarting) after suspending the fuel cell (particularly after suspending for a long period of time), or when power generation for a long period of time causes output characteristics such as electromotive force. Even when the value is lowered, the output characteristics of the fuel cell may be restored by performing the aging operation described above.

As a method of aging (break-in operation) of such a polymer electrolyte fuel cell, a step of flowing water to humidify the fuel cell and a residual in the membrane electrode assembly by generating power with the humidified fuel cell. A method of carrying out a step of removing impurities such as a solvent and an adhesive component has been proposed (see, for example, Patent Document 1 below).

Japanese Unexamined Patent Publication No. 2010-027430

By the way, examples of the controlling factor (passivation of the rate-determining state) of the aging (activation) time include humidification of the electrolyte membrane, activation of the catalyst (removal of the oxide film), and removal of contamination (removal of organic deposits, cleaning). In general, humidification of the electrolyte membrane and activation of the catalyst (removal of the oxide film) are performed in a relatively short time (for example, 10 minutes or less), so in order to shorten the aging time, how efficient is the contamination adsorbed on the catalyst. It is important to remove it well (see Fig. 4).

Further, the present inventors have described a cellified product manufactured through normal aging before and after, specifically, a UV curing step, a laminating step, a heating step, etc., and an aging completed cellified product after aging of the cellized product. As a result of LC-MS analysis of the adsorbed substances, it was confirmed that almost no organic oxides were detected after aging. That is, it is considered that the power generation performance is stabilized by removing this organic oxide by aging.

However, for example, as in the prior art described in Patent Document 1, simply supplying a reaction gas (humidified gas) humidified with water to a fuel cell causes organic deposits (organic oxidation) adhering to the catalyst surface. The thing) cannot be removed efficiently, and the time required for removing the organic deposits becomes long, so that the time required for the entire aging tends to be long.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an aging method for a polymer electrolyte fuel cell capable of effectively shortening the aging time.

In order to solve the above problems, the polymer electrolyte fuel cell aging method according to the present invention comprises a polymer electrolyte fuel cell having a membrane electrode assembly and a separator in which a pair of electrodes are arranged on both sides of an electrolyte membrane. A method for aging a polymer electrolyte fuel cell for aging, in which a reaction gas mixed with atomized alkaline electrolyzed water is circulated to the electrodes of the membrane electrode assembly, and the circulated reaction gas is distributed. It is characterized by the processing of using it to generate power and the execution of.

According to the present invention, by using alkaline electrolyzed water as the liquid used for humidification, organic deposits to be removed by aging can be efficiently washed, so that the conventional organic deposits are removed only by power generation. Aging can be performed in a shorter time than the method.

It is sectional drawing of the main part which shows an example of the solid polymer type fuel cell (fuel cell stack) to which the aging method of the solid polymer type combustion battery by this invention is applied. It is a schematic system block diagram which shows an example of the solid polymer type fuel cell (fuel cell stack) to which the aging method of the solid polymer type combustion battery by this invention is applied. (A) is a flowchart explaining an aging method of a polymer electrolyte fuel cell according to the present invention, and (B) is a flowchart explaining an aging method of a polymer electrolyte fuel cell according to a conventional method. It is a schematic diagram explaining the electrode (micro) state.

Hereinafter, the configuration of the present invention will be described in detail based on an example of an embodiment shown in the drawings. In the following, as an example, a case where the present invention is applied to a fuel cell mounted on a fuel cell vehicle or a fuel cell system including the present invention will be described as an example, but the scope of application is not limited to such an example. ..

[Structure of polymer electrolyte fuel cell (fuel cell stack)]
FIG. 1 is a cross-sectional view of a main part of a polymer electrolyte fuel cell (fuel cell stack) to which the aging method for a polymer electrolyte fuel cell according to the present invention is applied.

As shown in FIG. 1, a plurality of cells (cells) 1 which are basic units are stacked on the polymer electrolyte fuel cell (fuel cell stack) 10. Each cell 1 is a solid polymer fuel cell that generates an electromotive force by an electrochemical reaction between an oxidant gas (for example, air) and a fuel gas (for example, hydrogen). The cell 1 includes a MEGA 2 and a separator (fuel cell separator) 3 that contacts the MEGA 2 so as to partition the MEGA 2. In this embodiment, MEGA2 is sandwiched by a pair of separators 3 and 3.

The MEGA 2 is a combination of a membrane electrode assembly (MEA) 4 and gas diffusion layers 7a and 7b arranged on both sides thereof. The membrane electrode assembly 4 includes an electrolyte membrane 5 and a pair of electrodes 6a and 6b bonded so as to sandwich the electrolyte membrane 5. The electrolyte membrane 5 is made of a proton-conducting ion exchange membrane formed of a solid polymer material, and the electrodes 6a and 6b are formed of, for example, a porous carbon material carrying a catalyst such as platinum. The electrode 6a arranged on one side of the electrolyte membrane 5 serves as an anode, and the electrode 6b on the other side serves as a cathode. The gas diffusion layers 7a and 7b are formed of a gas-permeable conductive member such as a carbon porous body such as carbon paper or carbon cloth, or a metal porous body such as a metal mesh or foamed metal.

In the present embodiment, the MEGA 2 is the power generation unit of the polymer electrolyte fuel cell 10, and the separator 3 is in contact with the gas diffusion layers 7a and 7b of the MEGA 2. When the gas diffusion layers 7a and 7b are omitted, the membrane electrode assembly 4 is the power generation unit, and in this case, the separator 3 is in contact with the membrane electrode assembly 4. Therefore, the power generation unit of the polymer electrolyte fuel cell 10 includes the membrane electrode assembly 4 and comes into contact with the separator 3.

The separator 3 is a plate-shaped member made of a metal having excellent conductivity and gas impermeableness as a base material, and one side thereof is in contact with the gas diffusion layers 7a and 7b of MEGA2, and the other side is adjacent to the separator 3. It is in contact with the other surface side of the separator 3 of.

In the present embodiment, each separator 3 is formed in a wavy or uneven shape. The shape of the separator 3 is such that the shape of the wave is an isosceles trapezoid, the top of the wave is flat, and both ends of the top are angular at equal angles. That is, each separator 3 has substantially the same shape when viewed from the front side and the back side. The top of the separator 3 is in surface contact with one gas diffusion layer 7a of MEGA2, and the top of the separator 3 is in surface contact with the other gas diffusion layer 7b of MEGA2.

The gas flow path 21 defined between the gas diffusion layer 7a on the one electrode (that is, the anode) 6a side and the separator 3 is a flow path through which the fuel gas flows, and is on the other electrode (that is, the cathode) 6b side. The gas flow path 22 defined between the gas diffusion layer 7b and the separator 3 is a flow path through which the oxidizing agent gas flows. When the fuel gas is supplied to one of the gas flow paths 21 facing each other via the cell 1 and the oxidant gas is supplied to the gas flow path 22, an electrochemical reaction occurs in the cell 1 to generate an electromotive force.

Further, one cell 1 and another cell 1 adjacent thereto are arranged so that the electrode 6a serving as an anode and the electrode 6b serving as a cathode face each other. Further, the top of the back side of the separator 3 arranged along the electrode 6a which is the anode of a certain cell 1 and the top of the back side of the separator 3 arranged along the electrode 6b which is the cathode of another cell 1. And are in surface contact. Water as a refrigerant for cooling the cell 1 flows through the space 23 defined between the separators 3 and 3 that are in surface contact with each other between the two adjacent cells 1.

Further, a gasket (not shown) as a sealing member for sealing a fuel gas (for example, hydrogen) or an oxidant gas (for example, air) or cooling water is held between the ends of two adjacent cells 1. Has been done.

Further, in the solid polymer fuel cell 10 described above, as shown in FIG. 2, a fuel gas supply pipe 11a for supplying fuel gas to the electrode (anode) 6a side (gas flow path 21), and the fuel. A fuel gas discharge pipe 12a for discharging gas, an oxidant gas supply pipe 11b for supplying oxidant gas to the electrode (cathode) 6b side (gas flow path 22), and an oxidant gas discharge pipe 11b for discharging the oxidant gas. The oxidant gas discharge pipe 12b and the space 23 are connected to a cooling water pipe (not shown) for supplying and discharging water (cooling water) as a refrigerant.

[Aging method for polymer electrolyte fuel cell (fuel cell stack)]
In the polymer electrolyte fuel cell 10 having the above-mentioned configuration, in order to stabilize the power generation performance (output characteristics), for example, after assembling the polymer electrolyte fuel cell 10, aging (break-in operation) is performed. Will be.

Here, in order to shorten the aging time described above, it is effective to efficiently remove (clean) the contamination adsorbed on the catalyst, particularly the organic deposits (organic oxides), as described above.

Therefore, in the present embodiment, by mixing alkaline electrolyzed water with the humidified gas (humidified reaction gas) supplied to the anode 6a and the cathode 6b of the polymer electrolyte fuel cell 10, the performance-inhibiting substance adhering to the vicinity of the catalyst is present. By efficiently removing the organic deposits, aging (activation) is shortened.

Specifically, as shown in FIG. 2, the anode bubbler 15a is arranged in the fuel gas supply pipe 11a for supplying the fuel gas, and the anode bubbler 15a and the solid polymer fuel in the fuel gas supply pipe 11a downstream of the anode bubbler 15a (that is, the anode bubbler 15a in the fuel gas supply pipe 11a). A vaporizer 16a is arranged (between the anode 6a of the battery 10), and the alkaline electrolyzed water M previously stored in the reservoir 17a is supplied to the vaporizer 16a.

Further, the cathode bubbler 15b is arranged in the oxidant gas supply pipe 11b for supplying the oxidant gas, and the cathode bubbler 15b downstream of the cathode bubbler 15b (that is, the cathode bubbler 15b in the oxidant gas supply pipe 11b and the cathode 6b of the polymer electrolyte fuel cell 10) are arranged. The vaporizer 16b is arranged in the space between the two), and the alkaline electrolyzed water M previously stored in the reservoir 17b is supplied to the vaporizer 16b.

The anode bubbler 15a humidifies the fuel gas flowing through the fuel gas supply pipe 11a, and supplies the humidified fuel gas (humidifying gas) to the vaporizer 16a provided downstream thereof. The fuel gas flowing through the fuel gas supply pipe 11a is humidified by passing through the anode bubbler 15a, and the humidified fuel gas (humidified gas) and the alkaline electrolyzed water M supplied from the reservoir 17a are vaporized. It is atomized by the vessel 16a, mixed, and supplied to the anode 6a of the solid polymer fuel cell 10.

The cathode bubbler 15b humidifies the oxidant gas flowing through the oxidant gas supply pipe 11b, and supplies the humidified oxidant gas (humidifying gas) to the vaporizer 16b provided downstream thereof. The oxidant gas flowing through the oxidant gas supply pipe 11b is humidified by passing through the cathode bubbler 15b, and the humidified oxidant gas (humidifying gas) and the alkaline electrolyzed water M supplied from the reservoir 17b. Is atomized by the vaporizer 16b, mixed, and supplied to the cathode 6b of the solid polymer fuel cell 10.

The temperature inside the anode bubbler 15a and the cathode bubbler 15b is adjusted to a predetermined temperature by a heating means (not shown) or the like.

Further, as the alkaline electrolyzed water M mixed with the reaction gas (fuel gas, oxidant gas), for example, water obtained by electrolyzing city water or saline can be used. However, when an electrolyzed saline solution is used, the pH is high (for example, 11 or more) and the detergency is high, but there is a concern that the Na component may increase and damage to the electrolyte membrane may occur.

Further, the mixing ratio of the reaction gas (fuel gas, oxidant gas) and the alkaline electrolyzed water M in each of the vaporizers 16a and 16b can be appropriately set, and for example, the (mist) alkaline electrolyzed water M may be used. The pH of the mixed reaction gas can be set to be about 10 to 11.

With such a configuration, the alkaline electrolyzed water M is mixed with the humidified reaction gas (fuel gas, oxidant gas) supplied to the anode 6a and the cathode 6b of the polymer electrolyte fuel cell 10, and the reaction gas thereof. Since power generation (aging power generation) is performed using the fuel cell, it is possible to efficiently remove organic deposits which are performance-inhibiting substances adhering to the vicinity of the catalyst, and it is possible to shorten the aging time.

More specifically, the aging method of this embodiment is carried out according to the flow as shown in FIG. 3 (A).

That is, in the initial stage of the aging (activation) treatment, the vaporizers 16a and 16b are operated to sweep the current, and the vaporizers 16a and 16b (that is, the polymer electrolyte fuel) are operated from the reservoirs 17a and 17b. Alkaline electrolyzed water M is charged into the humidified reaction gas supplied to the anode 6a and the cathode 6b of the battery 10 (S11). At this time, as described above, the reaction gas (fuel gas, oxidant gas) humidified by the vaporizers 16a and 16b is mixed with the alkaline electrolyzed water M in the form of a mist to form the solid polymer fuel cell 10. It is distributed to the anode 6a and the cathode 6b. The pH of the reaction gas (reaction gas mixed with the alkaline electrolyzed water M) that is charged into the polymer electrolyte fuel cell 10 and flows through the anode 6a and the cathode 6b is, for example, about 10 to 11.

As a result, while power generation (aging power generation) is carried out by the polymer electrolyte fuel cell 10, the organic deposits adhering to the vicinity of the catalyst are washed.

After the above-mentioned treatment (treatment of S11) is continued for a predetermined time, the current sweeping is continued from the reservoirs 17a and 17b to the vaporizers 16a and 16b (that is, the anode 6a and the anode 6a of the polymer electrolyte fuel cell 10). The charging of the alkaline electrolyzed water M into the humidified reaction gas supplied to the cathode 6b) is stopped (S12).

As a result, rinse cleaning with the water generated by the power generation is carried out.

After continuing the above-mentioned processing (processing of S12) for a predetermined time, an output inspection or the like is performed (S13), and aging is completed.

The time required for the treatment of S11 and S12 described above depends on the electrode area, the time required for the Na component due to the difference in structure, and the like. For example, when the electrode area is about 250 cm ² , the time required for the treatment of S11 is 10 minutes. The power generation performance (output characteristics) is set to 5 minutes or more (preferably 10 minutes or more) for the processing of S12 (preferably 20 minutes or more) and 15 minutes or more for the processing of S11 and S12. ) Can be ensured by the present inventors.

In the conventional method shown in FIG. 3B (a method of sweeping the current without adding alkaline electrolyzed water and then performing an output inspection, etc.), it takes 30 minutes to perform the aging of the same structure as the above-mentioned one. Since it has been confirmed by the present inventors that the above is required, it can be said that the aging method of the present embodiment can complete the aging in about half the processing time as compared with the conventional method.

As described above, in the aging method of the present embodiment, by using alkaline electrolyzed water as the liquid used for humidification, organic deposits to be removed by aging can be efficiently washed, so that power generation can be performed. Only the aging can be performed in a short time as compared with the conventional method of removing organic deposits. In addition, the aging (activation) processing time due to power generation can be shortened, and not only productivity improvement but also capital investment and equipment space required for it can be reduced, which contributes to cost reduction.

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and there are design changes and the like within a range that does not deviate from the gist of the present invention. Also, they are included in the present invention.

1 ... cell (fuel cell), 2 ... MEGA, 3 ... separator, 4 ... membrane electrode junction (MEA), 5 ... electrolyte membrane, 6a ... electrode (anode), 6b ... electrode (cathode), 7a ... gas diffusion Layer (anode side), 7b ... gas diffusion layer (cathode side), 10 ... solid polymer fuel cell (fuel cell stack), 11a ... fuel gas supply pipe, 11b ... oxidant gas supply pipe, 12a ... fuel gas discharge Piping, 12b ... Oxidizing agent gas discharge piping, 15a ... Anode bubbler, 15b ... Cathode bubbler, 16a ... Vaporizer (cathode side), 16b ... Vaporizer (cathode side), 17a ... Reservoir (anode side), 17b ... Reservoir ( (Cathode side), 21 ... Gas flow path (anode side), 22 ... Gas flow path (cathode side), 23 ... Space through which water flows, M ... Alkaline electrolyzed water

Claims (2)

A method for aging a polymer electrolyte fuel cell for aging a polymer electrolyte fuel cell having a membrane electrode assembly and a separator in which a pair of electrodes are arranged on both sides of an electrolyte membrane.
A process of circulating a reaction gas mixed with atomized alkaline electrolyzed water to the electrodes of the membrane electrode assembly, and
The process of generating electricity using the reaction gas mixed with the distributed alkaline electrolyzed water, and
A process of stopping the addition of the alkaline electrolyzed water to the reaction gas and allowing the reaction gas, which is not mixed with the mist-like alkaline electrolyzed water, to flow to the electrode of the membrane electrode assembly.
A method for aging a polymer electrolyte fuel cell, which comprises performing a process of generating electricity using a reaction gas that does not mix the distributed alkaline electrolyzed water. The time required for the process of generating power using the reaction gas not mixed with the alkaline electrolyzed water is shorter than the time required for the process of generating power using the reaction gas mixed with the alkaline electrolyzed water. The method for aging a polymer electrolyte fuel cell according to claim 1.

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