Fuel cell activation device

Abstract

The problem addressed by the present invention is that of achieving a higher activation effect than conventional non-power generation methods at a lower cost than conventional power generation methods. In order to solve the problem, the fuel cell activation device of the present invention activates the fuel cell cells. A fuel cell is provided with an anode layer, an electrolyte membrane, and a cathode layer in this order from one side. Platinum is contained as a catalyst in the anode layer and the cathode layer. A fuel cell activation device is provided with an anode-side gas supply device, a cathode-side gas supply device, and a potential scanning circuit. In a fuel cell activation device, fuel cells are activated by supplying a fuel gas to an anode layer by means of an anode-side gas supply device, supplying a low-oxygen gas to a cathode layer by means of a cathode-side gas supply device, and controlling the potential of the cathode layer by means of a potential scanning circuit.

Description

Technical Field

[0001] The present invention relates to a device for activating a fuel cell single cell. Background Art

[0002] In a fuel cell single cell, an anode layer, an electrolyte membrane, and a cathode layer are provided in sequence from one side. In the anode layer and the cathode layer, platinum is included as a catalyst. During power generation, a fuel gas containing hydrogen is humidified and supplied to the anode layer. On the other hand, an oxidizing gas containing oxygen is humidified and supplied to the cathode layer.

[0003] [Prior Art Documents]

[0004] (Patent Document)

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2023-161181 Summary of the Invention

[0006] [Problems to be Solved by the Invention]

[0007] In such a fuel cell single cell, the performance is mostly insufficient just after manufacturing. As reasons therefor, it can be cited that the ionomer in the anode-side catalyst layer, the electrolyte membrane, or the cathode-side catalyst layer is not sufficiently wetted, or there are attachments adhering to platinum. Therefore, before the fuel cell stack is shipped, it is necessary to activate each fuel cell single cell. As a method for its activation, there are the following power generation method and non-power generation method.

[0008] In the power generation method, the fuel gas is actually humidified and supplied to the anode layer, and the oxidizing gas is also actually humidified and supplied to the cathode layer, and the anode layer and the cathode layer are electrically connected via a load, thereby actually generating power. By the ion flow accompanying this power generation and the generated water, the attachments adhering to platinum are washed away to activate the fuel cell single cell. Further, at this time, the moisture in the fuel gas and the oxidizing gas is supplied to the anode layer, the electrolyte membrane, and the cathode layer, so that the fuel cell single cell is wetted, thereby also activating the fuel cell single cell. However, since this power generation method actually generates power, it has a high output. Therefore, the cost of the fuel cell activation device main body or its operation is high.

[0009] On the other hand, in the non-power generation method, the fuel gas is actually humidified and supplied to the anode layer. On the other hand, an oxygen-free inert gas is humidified and supplied to the cathode layer, and an external device is used to control the potential. That is, when the fuel gas is supplied to the anode layer and the cathode potential is controlled by a potential sweep circuit, a proton pump is generated, which is a phenomenon in which hydrogen ions dissociated from hydrogen molecules in the fuel gas move through the electrolyte membrane to the cathode layer. The hydrogen ions that move to the cathode layer through this proton pump combine with the electrons that move to the cathode layer through the load circuit to form hydrogen molecules. Through the above series of processes, the proton pump is carried out.

[0010] According to this non-power generation method, since no oxidizing gas is supplied to the cathode layer, the output of the fuel cell single cell can be suppressed compared with the power generation method. On the other hand, since the fuel gas is supplied to the anode layer, a proton pump can be generated. Therefore, according to the non-power generation method, while suppressing the output of the fuel cell single cell, moisture moves with the movement of hydrogen ions caused by the proton pump, and the fuel cell single cell becomes wet. Therefore, compared with the power generation method, the fuel cell single cell can be activated with a low output. However, the activation effect of the fuel cell single cell is lower than that of the power generation method.

[0011] The present invention has been completed in view of the above circumstances, and an object thereof is to achieve a higher activation effect than the conventional non-power generation method at a lower cost than the conventional power generation method.

[0012] [Technical means for solving the problem]

[0013] The present inventors have found that the above object can be achieved by supplying a low-oxygen gas to the cathode layer during the proton pump, and thus completed the present invention. The present invention is the following fuel cell activation devices (1) and (2).

[0014] (1) A fuel cell activation device that activates a fuel cell single cell, the fuel cell single cell including an anode layer, an electrolyte membrane, and a cathode layer in sequence from one side, and containing platinum as a catalyst in the anode layer and the cathode layer. The fuel cell activation device includes: an anode-side gas supply device configured to supply a fuel gas, which is a gas containing hydrogen, to the anode layer; a cathode-side gas supply device configured to supply a low-oxygen gas, which is a gas having an oxygen concentration lower than that of air, to the cathode layer; and a potential sweep circuit configured to control the potential of the fuel cell single cell. And, the fuel gas is supplied to the anode layer by the anode-side gas supply device, the low-oxygen gas is supplied to the cathode layer by the cathode-side gas supply device, and the potential of the cathode layer is controlled by the potential sweep circuit, thereby activating the fuel cell single cell.

[0015] This structure generates a proton pump by supplying fuel gas to the anode layer and controlling the potential of the cathode layer using a potential scanning circuit. Hydrogen ions transported to the cathode layer by this proton pump combine with oxygen in the low-oxygen gas on the surface of the platinum catalyst, generating water. This water cleanses deposits adhering to the platinum within the cathode layer. Furthermore, the generated water moistens the fuel cell. This achieves a higher activation effect than conventional proton pumps that supply inert gas to the cathode layer.

[0016] Furthermore, since low-oxygen gas is supplied to the cathode layer, the cathode stoichiometric ratio is lower than when air is supplied. Furthermore, the cathode stoichiometric ratio here refers to the optimal ratio of the amount of gas supplied to the anode layer to the amount of gas supplied to the cathode layer. By reducing the cathode stoichiometric ratio in this way, the fuel gas supply can be reduced, thereby suppressing the output of the fuel cell unit. This allows the fuel cell activation device to be miniaturized, further reducing costs compared to previous power generation methods.

[0017] As described above, according to this configuration, by supplying a low-oxygen gas to the cathode layer during proton pumping, a higher activation effect than conventional non-power generation methods can be achieved at a lower cost than conventional power generation methods.

[0018] (2) The fuel cell activation device according to (1) above, wherein the cathode-side gas supply device supplies air and nitrogen to the cathode layer, thereby supplying the low-oxygen gas to the cathode layer.

[0019] According to this configuration, the low-oxygen gas can be supplied to the cathode layer simply and inexpensively.

[0020] (Effects of the Invention)

[0021] As described above, according to the structure of (1), a higher activation effect than the conventional non-power generation method can be achieved at a lower cost than the conventional power generation method. Furthermore, according to the structure of (2) cited from (1), respective additional effects can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram showing a fuel cell activation device according to a first embodiment.

[0023] Figure 2 This is a schematic diagram showing the state of a fuel cell being activated by a fuel cell activation device.

[0024] Figure 3 This is a schematic diagram showing the state of a comparative fuel cell during activation.

[0025] Figure 4This is a schematic diagram showing the state during power generation of a single fuel cell. Detailed Embodiment

[0026] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to any of the following embodiments and can be appropriately modified without departing from the gist of the present invention.

[0027] (First Embodiment)

[0028] Figure 1 The shown fuel cell activation device 80 is provided corresponding to the fuel cell stack 50s. A plurality of fuel cell monomers 50 are housed in the fuel cell stack 50s.

[0029] As Figure 4 shown, each fuel cell monomer 50 sequentially includes an anode layer 20, an electrolyte membrane 30, and a cathode layer 40 from one side. The anode layer 20 includes an anode-side gas diffusion layer 22 and an anode-side catalyst layer 25 provided on the side closer to the electrolyte membrane 30 than the anode-side gas diffusion layer 22. The cathode layer 40 includes a cathode-side gas diffusion layer 42 and a cathode-side catalyst layer 45 provided on the side closer to the electrolyte membrane 30 than the cathode-side gas diffusion layer 42. Both the anode-side gas diffusion layer 22 and the cathode-side gas diffusion layer 42 are mainly composed of a porous layer. In the anode-side catalyst layer 25 and the cathode-side catalyst layer 45, platinum Pt is included as a catalyst.

[0030] During power generation, the anode layer 20 and the cathode layer 40 are electrically connected via a circuit 60c including a power supply object 60. Hereinafter, the gas containing hydrogen will be referred to as "fuel gas Gh", and the gas containing oxygen will be referred to as "oxidizing gas Go". In addition, the oxidizing gas Go mentioned here is air and contains nitrogen and oxygen. During power generation, the fuel gas Gh is humidified and supplied to the anode-side gas diffusion layer 22, and the oxidizing gas Go is humidified and supplied to the cathode-side gas diffusion layer 42.

[0031] Hydrogen ions H + , dissociate from hydrogen molecules H2 in the fuel gas Gh in the anode-side gas diffusion layer 22 and flow into the anode-side catalyst layer 25, and electrons e dissociate and flow into the circuit 60c. In addition, in this reaction, platinum Pt serves as a catalyst. The hydrogen ions H that flow into the anode-side catalyst layer 25 + , move through the electrolyte membrane 30 to the cathode-side catalyst layer 45. Hereinafter, such a phenomenon will be referred to as "proton pump". On the other hand, the aforementioned electrons e flow from the anode layer 20 side in the circuit 60c toward the cathode layer 40 side.

[0032] The hydrogen ions H that move to the cathode-side catalyst layer 45 +, it combines with the oxygen atoms O dissociated from the oxygen molecules O2 in the oxidation gas Go and the electrons e from the circuit 60c in the cathode-side gas diffusion layer 42 to form water molecules H2O. These water molecules H2O diffuse into the cathode-side gas diffusion layer 42. Through the above series of processes, power generation is carried out.

[0033] Regarding the fuel cell single cell 50 shown above, generally, its performance is insufficient just after manufacturing. As reasons therefor, it can be cited that the ionomer in the anode-side catalyst layer 25, the electrolyte membrane 30, or the cathode-side catalyst layer 45 is not sufficiently wetted, or an attachment d adheres to platinum Pt. Thus, Figure 1 before the fuel cell stack 50s shown is shipped, it is necessary to activate each fuel cell single cell 50. The device for this activation is the fuel cell activation device 80.

[0034] As Figure 1 shown, the fuel cell activation device 80 includes an anode-side gas supply device 82, a cathode-side gas supply device 84, a potential sweep circuit 83, a cooling device 86, a voltmeter 87, and a control device 88. The anode-side gas supply device 82 and the cathode-side gas supply device 84 each include humidifiers 82w, 84w that generate water vapor. The control device 88 controls the anode-side gas supply device 82, the cathode-side gas supply device 84, the potential sweep circuit 83, and the cooling device 86.

[0035] The voltmeter 87 is configured to be able to measure the output voltage of each fuel cell single cell 50. The output voltage of each fuel cell single cell 50 measured by this voltmeter 87 is input to the control device 88.

[0036] The cooling device 86 cools each fuel cell single cell 50 by circulating a refrigerant between the fuel cell stack 50s and a radiator. The control device 88 controls the temperature of each fuel cell single cell 50 to a temperature at which activation is easily carried out through the control of this cooling device 86.

[0037] As Figure 2 shown, the electrode of the anode layer 20 and the electrode of the cathode layer 40 are electrically connected via a circuit 83c including the potential sweep circuit 83. The potential sweep circuit 83 is configured to be able to control the potential of the fuel cell single cell 50. Specifically, the fuel cell single cell 50 applies an external force for activating each fuel cell single cell 50 by controlling the potential of the cathode layer 40 relative to the anode layer 20.

[0038] The anode-side gas supply device 82 is configured to be able to supply the fuel gas Gh humidified by the humidifier 82w to the anode-side gas diffusion layer 22. The control device 88 controls the flow rate and pressure of the fuel gas Gh supplied to the anode layer 20 through the control of this anode-side gas supply device 82.

[0039] Hereinafter, a gas with an oxygen concentration lower than that of air is referred to as "low-oxygen gas Gc". The cathode stoichiometry in this low-oxygen gas Gc is preferably 1.0 or less. In addition, the "cathode stoichiometry" as mentioned herein is the optimal ratio of the amount of gas supplied to the anode layer 20 to the amount of gas supplied to the cathode layer 40.

[0040] The cathode-side gas supply device 84 is configured to be able to supply the low-oxygen gas by supplying air and nitrogen N2 to the cathode-side gas diffusion layer 42 together. Additionally, at this time, water vapor generated by the humidifier 84w is also supplied together, thereby being configured to be able to humidify the low-oxygen gas Gc. That is, the cathode-side gas supply device 84 is configured to be able to supply the humidified low-oxygen gas Gc to the cathode-side gas diffusion layer 42. The control device 88 controls the flow rate and pressure of the low-oxygen gas Gc supplied to the cathode layer 40 by controlling the cathode-side gas supply device 84.

[0041] The control device 88, by Figure 2 the anode-side gas supply device 82 shown, humidifies and supplies the fuel gas Gh to the anode-side gas diffusion layer 22, and by the cathode-side gas supply device 84, humidifies and supplies the low-oxygen gas Gc to the cathode-side gas diffusion layer 42, and controls the cathode potential using the potential sweep circuit 83. Thereby, a proton pump is generated.

[0042] Hereinafter, as Figure 3 shown, when operating the proton pump, the method of supplying nitrogen Gn instead of the low-oxygen gas Gc from the cathode-side gas supply device 84 to the cathode-side gas diffusion layer 42 is referred to as the comparative method. That is, in this comparative method, the activation of the fuel cell single body 50 based on the non-power generation method is performed.

[0043] In the case of this comparative method, hydrogen ions H + dissociate from hydrogen molecules H2 in the fuel gas Gh in the anode-side gas diffusion layer 22 and flow into the anode-side catalyst layer 25, and electrons e dissociate and flow into the circuit 83c. Additionally, in this reaction, platinum Pt serves as a catalyst. The hydrogen ions H that flow into the anode-side catalyst layer 25 + move through the electrolyte membrane 30 to the cathode-side catalyst layer 45. On the other hand, the aforementioned electrons e flow from the anode layer 20 side in the circuit 83c toward the cathode layer 40 side.

[0044] The hydrogen ions H that move to the cathode-side catalyst layer 45 + combine with the electrons e from the circuit 83c to form hydrogen molecules H2. These hydrogen molecules H2 diffuse into the cathode-side gas diffusion layer 42. Due to the ion flow accompanying the above proton pump, water H2O moves, causing the fuel cell single body 50 to become moist.

[0045] However, different from the power generation method, in the cathode layer 40, water molecules H2O are not generated from hydrogen ions H + Therefore, the attachment d on platinum Pt is not washed away by the generated water molecules H2O. In addition, the ionomer of the cathode-side diffusion layer 42 is not wetted by the generated water molecules H2O. Therefore, the activation effect of the fuel cell unit 50 is lower than that of the power generation method.

[0046] Regarding this point, in the Figure 2 present embodiment shown, during proton pumping, the cathode-side gas supply device 84 supplies the low-oxygen gas Gc instead of nitrogen Gn to the cathode-side gas diffusion layer 42.

[0047] Similarly in the case of the present embodiment, hydrogen ions H + dissociate from hydrogen molecules H2 in the fuel gas Gh in the anode-side gas diffusion layer 22 and flow into the anode-side catalyst layer 25, and electrons e dissociate and flow into the circuit 83c. The hydrogen ions H + flowing into the anode-side catalyst layer 25 move to the cathode-side catalyst layer 45 through the electrolyte membrane 30. On the other hand, the aforementioned electrons e flow from the anode layer 20 side in the circuit 83c toward the cathode layer 40 side. So far, it is the same as the case of the above comparison method.

[0048] The hydrogen ions H + that move to the cathode-side catalyst layer 45 combine with oxygen atoms O dissociated from oxygen molecules O2 in the low-oxygen gas Gc in the cathode-side gas diffusion layer 42 and electrons e from the circuit 60c to form water molecules H2O. The attached substance d attached to platinum Pt is washed with this water H2O. As a result, the effective catalyst surface area of platinum Pt increases, and the fuel cell unit 50 is activated.

[0049] Furthermore, in the present embodiment, since water molecules H2O are generated in the cathode layer 40, the ionomer of the cathode-side catalyst layer 45 is more easily wetted, and the fuel cell unit 50 is more easily activated.

[0050] Hereinafter, the structure and effects of the present embodiment will be summarized.

[0051] According to the present embodiment, as Figure 2 shown, by supplying the fuel gas Gh to the anode layer 20 and controlling the potential of the cathode layer 40, a proton pump is generated. The hydrogen ions H + that move to the cathode layer 40 through this proton pump combine with oxygen O2 in the low-oxygen gas Gc, thereby generating water H2O. This water H2O cleans the attachment on platinum Pt in the cathode layer 40. In addition, the fuel cell unit 50 is wetted by generating water H2O. Thus, an activation effect higher than that of the comparison method using the non-power generation method can be achieved.

[0052] Moreover, at this time, since the low-oxygen gas Gc is supplied to the cathode layer 40, the stoichiometric ratio is lower than in the case of supplying air. By thus reducing the stoichiometric ratio, the supply amount of the fuel gas Gh can be suppressed, and the output of the fuel cell single cell 50 can be suppressed. Thereby, the size of the main body of the fuel cell activation device 80 can be reduced, and the cost can be suppressed as compared with the case of supplying air to the cathode layer 40, that is, as compared with the power generation method.

[0053] As described above, according to the present embodiment, an activation effect higher than that of the non-power generation method can be achieved at a lower cost than the power generation method.

[0054] Furthermore, the cathode-side gas supply device 84 can supply the low-oxygen gas Gc to the cathode layer 40 simply and inexpensively by supplying air and nitrogen N2 to the cathode layer 40.

[0055] (Other Embodiments)

[0056] The embodiments shown above can be modified as follows, for example. Figure 2 The shown potential sweep circuit 83 may be configured to be able to apply a negative voltage to the cathode layer 40 with respect to the anode potential. And the control device 88 may make the potential of the cathode layer 40 negative by the potential sweep circuit 83 during proton pumping. In this case, the platinum Pt of the anode layer 20 and the cathode layer 40 is likely to be negatively charged. Therefore, a repulsive force is likely to be generated between the platinum Pt and the attachment d. This is because there are many substances with a negative charge attached to the platinum Pt. Thereby, the attachment d is likely to float from the platinum Pt, and the attachment d is more easily washed away from the platinum Pt.

[0057] Reference Numerals

[0058] 20: Anode layer

[0059] 30: Electrolyte membrane

[0060] 40: Cathode layer

[0061] 50: Fuel cell single cell

[0062] 80: Fuel cell activation device

[0063] 82: Anode-side gas supply device

[0064] 83: Potential sweep circuit

[0065] 84: Cathode-side gas supply device

[0066] Gh: Fuel gas

[0067] Gc: Low-oxygen gas

[0068] Pt: Platinum

Claims

1. A fuel cell activation device that activates a fuel cell unit. The fuel cell unit sequentially includes an anode layer, an electrolyte membrane, and a cathode layer from one side, and platinum as a catalyst is included in the anode layer and the cathode layer. The fuel cell activation device includes: An anode-side gas supply device configured to supply a fuel gas, which is a gas containing hydrogen, to the anode layer; A cathode-side gas supply device configured to supply a low-oxygen gas, which is a gas having a lower oxygen concentration than air, to the cathode layer; and A potential scanning circuit configured to control the potential of the fuel cell unit; and By supplying the fuel gas to the anode layer using the anode-side gas supply device, supplying the low-oxygen gas to the cathode layer using the cathode-side gas supply device, and controlling the potential of the cathode layer using the potential scanning circuit, the fuel cell unit is activated.

2. The fuel cell activation device according to claim 1, wherein, The cathode-side gas supply device supplies air and nitrogen to the cathode layer, thereby supplying the low-oxygen gas to the cathode layer.

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