Fuel cell activation device

Abstract

To achieve a higher activation effect than a conventional non-power generation method at lower cost than a conventional power generation method.SOLUTION: A fuel cell activation device activates a fuel cell. The fuel cell includes, from one side to the other, an anode layer, an electrolyte membrane, and a cathode layer. The anode layer and the cathode layer contain platinum as a catalyst. The fuel cell activation device includes an anode-side gas supply device, a cathode-side gas supply device, and a potential scanning circuit. The fuel cell activation device activates the fuel cell by supplying fuel gas to the anode layer via the anode-side gas supply device and low-oxygen gas to the cathode layer via the cathode-side gas supply device, and by controlling the cathode potential via the potential scanning circuit.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This invention relates to a device for activating fuel cell cells. [Background technology]

[0002] Some fuel cell cells consist of an anode layer, an electrolyte membrane, and a cathode layer, arranged in that order from one side to the other. The anode and cathode layers contain platinum as a catalyst. During power generation, a humidified fuel gas containing hydrogen is supplied to the anode layer. On the other hand, a humidified oxidizing gas containing oxygen is supplied to the cathode layer. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-161181 [Overview of the project] [Problems that the invention aims to solve]

[0004] Such fuel cell cells often exhibit insufficient performance immediately after manufacturing. This is due to insufficient wetting of the ionomer in the anode catalyst layer, electrolyte membrane, and cathode catalyst layer, as well as the presence of deposits on the platinum. For these reasons, each fuel cell needs to be activated before the fuel cell stack is shipped. The following methods exist for this activation: a power generation method and a non-power generation method.

[0005] In this power generation method, fuel gas is actually humidified and supplied to the anode layer, and oxidizing gas is also actually supplied to the cathode layer. Electrical connection is made between the anode and cathode layers via a load to generate electricity. The ion flow and generated water from this power generation wash away deposits attached to the platinum, activating the fuel cell. Furthermore, at this time, moisture from the fuel gas and oxidizing gas is supplied to the anode layer, electrolyte membrane, and cathode layer, wetting the fuel cell and activating it further. However, because this power generation method actually generates electricity, it is high-output. Consequently, the cost of the fuel cell activation device itself and its operation are high.

[0006] On the other hand, in the non-power generation method, fuel gas is actually humidified and supplied to the anode layer, while an oxygen-free inert gas is humidified and supplied to the cathode layer, and the potential is controlled using an external device. That is, when fuel gas is supplied to the anode layer and the cathode potential is controlled by a potential scanning circuit, a proton pump occurs, 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 have moved to the cathode layer by this proton pump combine with electrons that have moved to the cathode layer through the load circuit to form hydrogen molecules. The proton pump is performed by this series of processes.

[0007] This non-power generation method does not supply oxidizing gas to the cathode layer, thus reducing the output of the fuel cell compared to the power generation method. On the other hand, since fuel gas is supplied to the anode layer, proton pumps can still be generated. Therefore, with this non-power generation method, even though the output of the fuel cell is reduced, moisture moves along with the movement of hydrogen ions by the proton pump, humidifying the fuel cell. As a result, the fuel cell can be activated at a lower output compared to the power generation method. However, the activation effect on the fuel cell is lower compared to the power generation method.

[0008] This invention has been made in view of the above circumstances, and aims to enable the realization of a higher activation effect than conventional non-power generation methods at a lower cost than conventional power generation methods. [Means for solving the problem]

[0009] The inventors of the present invention discovered that the above objective can be achieved by supplying a low-oxygen gas to the cathode layer during proton pump operation, and thus arrived at the present invention. The present invention is a fuel cell activation device as described in (1) and (2) below.

[0010] (1) A fuel cell activation device for activating a fuel cell, which comprises, in order from one side, an anode layer, an electrolyte membrane, and a cathode layer, wherein the anode layer and the cathode layer contain platinum as a catalyst, an anode-side gas supply device configured to supply fuel gas, which contains hydrogen, to the anode layer, A cathode-side gas supply device configured to supply a low-oxygen gas, which has a lower oxygen concentration than air, to the cathode layer, A potential scanning circuit configured to control the potential of a fuel cell is provided, The fuel cell is activated 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. Fuel cell activation device.

[0011] In this configuration, fuel gas is supplied to the anode layer, and the potential of the cathode layer is controlled by a potential scanning circuit, thereby generating a proton pump. Hydrogen ions that move 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 cleans deposits attached to the platinum in the cathode layer. In addition, the fuel cell cell is wetted by the generated water. As a result, a higher activation effect can be achieved compared to conventional proton pumps that supply inert gas to the cathode layer.

[0012] Moreover, at this time, since low-oxygen gas is supplied to the cathode layer, the cathode stoichiometry is lower than when air is supplied. Here, the cathode stoichiometry is 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 stoichiometry in this way, the supply amount of the fuel gas can be suppressed, and the output of the fuel cell can be suppressed. As a result, the fuel cell activation device main body can be miniaturized, and the cost can be suppressed compared with the conventional power generation method.

[0013] As described above, according to this configuration, by supplying low-oxygen gas to the cathode layer during proton pumping, it becomes possible to realize an activation effect higher than that of the conventional non-power generation method at a cost lower than that of the conventional power generation method.

[0014] (2) The cathode-side gas supply device supplies the low-oxygen gas to the cathode layer by supplying air and nitrogen to the cathode layer. The fuel cell activation device according to (1) above.

[0015] According to this configuration, low-oxygen gas can be supplied to the cathode layer simply and at low cost.

Effects of the Invention

[0016] As described above, according to the configuration of (1) above, it becomes possible to obtain an activation effect higher than that of the conventional non-power generation method at a cost lower than that of the conventional power generation method. Furthermore, according to the configuration of (2) that cites (1) above, respective additional effects can be obtained.

Brief Description of the Drawings

[0017] [Figure 1] It is a schematic diagram showing the fuel cell activation device of the first embodiment. [Figure 2] It is a schematic diagram showing a state during activation of a fuel cell by a fuel cell activation device. [Figure 3]It is a schematic diagram showing the state during activation of a fuel cell by a comparative form. [Figure 4] It is a schematic diagram showing the state during power generation by a fuel cell.

Mode for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments, and can be appropriately modified and implemented without departing from the gist of the present invention.

[0019] [First Embodiment] The fuel cell activation device 80 shown in FIG. 1 is installed with respect to the fuel cell stack 50s. A plurality of fuel cells 50 are stored in the fuel cell stack 50s.

[0020] As shown in FIG. 4, each fuel cell 50 includes, in order from one side, an anode layer 20, an electrolyte membrane 30, and a cathode layer 40. The anode layer 20 includes an anode-side gas diffusion layer 22 and an anode-side catalyst layer 25 provided closer to the electrolyte membrane 30 side 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 closer to the electrolyte membrane 30 side 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 porous layers. The anode-side catalyst layer 25 and the cathode-side catalyst layer 45 contain platinum Pt as a catalyst. <s

[0021] During power generation, the anode layer 20 and the cathode layer 40 are electrically connected via a circuit 60c including a power supply target 60. Hereinafter, a gas containing hydrogen is referred to as "fuel gas Gh", and a gas containing oxygen is referred to as "oxidizing gas Go". The oxidizing gas Go 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.

[0022] From hydrogen molecules H2 in the fuel gas Gh in the anode-side gas diffusion layer 22, hydrogen ions H2 + The hydrogen ions H dissociate and flow into the anode-side catalyst layer 25, while the electrons e dissociate and flow into the circuit 60c. Platinum Pt acts as the catalyst in this reaction. Hydrogen ions H flow into the anode-side catalyst layer 25. + The electrons move through the electrolyte membrane 30 to the cathode-side catalyst layer 45. Hereafter, this phenomenon will be referred to as a "proton pump." On the other hand, the aforementioned electrons e flow from the anode layer 20 side to the cathode layer 40 side in the circuit 60c.

[0023] Hydrogen ions H that have moved to the cathode-side catalyst layer 45 + In the cathode-side gas diffusion layer 42, oxygen atoms O dissociated from oxygen molecules O2 in the oxidizing gas Go combine with electrons e from circuit 60c to form water molecules H2O. These water molecules H2O then diffuse into the cathode-side gas diffusion layer 42. Through this series of processes, electricity is generated.

[0024] The fuel cell cells 50 described above generally have insufficient performance immediately after manufacturing. This is because the ionomer is not sufficiently wetted in the anode-side catalyst layer 25, the electrolyte membrane 30, and the cathode-side catalyst layer 45, and because deposits d are attached to the platinum Pt. For these reasons, each fuel cell 50 needs to be activated before the fuel cell stack 50s shown in Figure 1 is shipped. The device used for this activation is the fuel cell activation device 80.

[0025] As shown in Figure 1, the fuel cell activation device 80 includes an anode-side gas supply device 82, a cathode-side gas supply device 84, a potential scanning 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 are each equipped with humidifiers 82w and 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 scanning circuit 83, and the cooling device 86.

[0026] The voltmeter 87 is configured to measure the output voltage of each fuel cell 50. The output voltage of each fuel cell 50 measured by the voltmeter 87 is input to the control device 88.

[0027] The cooling device 86 cools each fuel cell 50 by circulating a coolant between the fuel cell stack 50s and the radiator. The control device 88 controls the temperature of each fuel cell 50 to a temperature that facilitates activation by controlling the cooling device 86.

[0028] As shown in Figure 2, the electrodes of the anode layer 20 and the electrodes of the cathode layer 40 are electrically connected via a circuit 83c including a potential scanning circuit 83. The potential scanning circuit 83 is configured to control the potential of the fuel cell 50. Specifically, the fuel cell 50 applies an external force to activate each fuel cell 50 by controlling the potential of the cathode layer 40 relative to the anode layer 20.

[0029] The anode-side gas supply device 82 is configured to supply 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 by controlling this anode-side gas supply device 82.

[0030] Hereinafter, a gas with a lower oxygen concentration than air will be referred to as "low-oxygen gas Gc". The cathode-stoichiometric ratio in this low-oxygen gas Gc is preferably 1.0 or less. The "cathode-stoichiometric ratio" here refers to 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.

[0031] The cathode-side gas supply device 84 is configured to supply low-oxygen gas to the cathode-side gas diffusion layer 42 by supplying air together with nitrogen gas N2. Furthermore, it is configured to humidify the low-oxygen gas Gc by supplying water vapor generated by the humidifier 84w at the same time. In other words, the cathode-side gas supply device 84 is configured to supply 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.

[0032] The control device 88 humidifies fuel gas Gh using the anode-side gas supply device 82 shown in Figure 2 and supplies it to the anode-side gas diffusion layer 22, and humidifies low-oxygen gas Gc using the cathode-side gas supply device 84 and supplies it to the cathode-side gas diffusion layer 42, while controlling the cathode potential with the potential scanning circuit 83. This generates a proton pump.

[0033] As shown in Figure 3 below, the comparative configuration is defined as the one in which, during proton pump operation, the cathode-side gas supply device 84 supplies nitrogen gas Gn instead of low-oxygen gas Gc to the cathode-side gas diffusion layer 42. In other words, in this comparative configuration, the fuel cell cell 50 is activated by a non-power generation method.

[0034] In this comparative configuration, hydrogen molecules H2 in the fuel gas Gh in the anode-side gas diffusion layer 22 are converted to hydrogen ions H + The hydrogen ions H dissociate and flow into the anode-side catalyst layer 25, while the electrons e dissociate and flow into circuit 83c. Platinum Pt acts as the catalyst for this reaction. Hydrogen ions H flow into the anode-side catalyst layer 25. + These electrons pass through the electrolyte membrane 30 and move to the cathode-side catalyst layer 45. On the other hand, the aforementioned electrons e flow from the anode layer 20 side to the cathode layer 40 side in the circuit 83c.

[0035] Hydrogen ions H that have moved to the cathode-side catalyst layer 45 +It combines with an electron e from the circuit 83c to form a hydrogen molecule H2. The hydrogen molecule H2 diffuses into the cathode-side gas diffusion layer 42. Due to the flow of ions associated with the above proton pump, water H2O moves and the fuel cell 50 becomes wet.

[0036] However, unlike the power generation method, in the cathode layer 40, water molecules H2O are not generated from hydrogen ions H + So, the deposit d of platinum Pt is not washed away by the generated water molecules H2O. Also, 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 50 is lower compared to the power generation method.

[0037] In this regard, in the present embodiment shown in FIG. 2, during the proton pump, the cathode-side gas supply device 84 supplies low-oxygen gas Gc instead of nitrogen gas Gn to the cathode-side gas diffusion layer 42.

[0038] Even in the case of this embodiment, from the hydrogen molecules H2 in the fuel gas Gh in the anode-side gas diffusion layer 22, hydrogen ions H + dissociate and flow into the anode-side catalyst layer 25, and electrons e dissociate and flow into the circuit 83c. 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 to the cathode layer 40 side in the circuit 83c. So far, it is the same as in the case of the aforementioned comparative form.

[0039] The hydrogen ions H <00,00010>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 water H2O washes away the deposits d adhering to the platinum Pt. Thereby, the effective catalyst surface area of the platinum Pt increases, and the fuel cell 50 is activated.

[0040] Furthermore, in this embodiment, since water molecules H2O are generated in the cathode layer 40, the ionomer of the cathode-side catalyst layer 45 becomes more easily wetted, and the fuel cell cell 50 becomes more easily activated.

[0041] The configuration and effects of this embodiment are summarized below.

[0042] According to this embodiment, as shown in Figure 2, a proton pump is generated by supplying fuel gas Gh to the anode layer 20 and controlling the potential of the cathode layer 40. Hydrogen ions H move to the cathode layer 40 by this proton pump. + However, by combining with oxygen O2 in the low-oxygen gas Gc, water H2O is generated. This water H2O washes away deposits attached to the platinum Pt within the cathode layer 40. In addition, the generated water H2O wets the fuel cell cell 50. As a result, a higher activation effect can be achieved compared to the comparative method which does not generate electricity.

[0043] Furthermore, since low-oxygen gas Gc is supplied to the cathode layer 40 at this time, the stoichiometric ratio becomes lower than when air is supplied. This lower stoichiometric ratio allows for a reduction in the amount of fuel gas Gh supplied, thereby reducing the output of the fuel cell cell 50. As a result, the fuel cell activator 80 can be miniaturized, and costs can be reduced compared to when air is supplied to the cathode layer 40, that is, compared to the power generation method.

[0044] As described above, according to this embodiment, it is possible to achieve a higher activation effect than non-power generation methods at a lower cost than power generation methods.

[0045] Furthermore, the cathode-side gas supply device 84 can supply low-oxygen gas Gc to the cathode layer 40 easily and inexpensively by supplying air and nitrogen N2 to the cathode layer 40.

[0046] [Other embodiments] The embodiments described above can be modified as follows, for example. The potential scanning circuit 83 shown in Figure 2 may be configured to apply a negative voltage to the cathode layer 40 relative to the anode potential. The control device 88 may then make the potential of the cathode layer 40 negative using the potential scanning circuit 83 during proton pump operation. In this case, the platinum Pt of the anode layer 20 and the cathode layer 40 will be more likely to become negatively charged. As a result, a repulsive force will be more likely to occur between the platinum Pt and the deposits d. This is because many of the deposits d that adhere to platinum Pt are negatively charged. Consequently, the deposits d will be more likely to float away from the platinum Pt, and the deposits d will be more easily washed away from the platinum Pt. [Explanation of Symbols]

[0047] 20 anode layers 30 Electrolyte membrane 40 Cathode Layers 50 fuel cell cells 80 Fuel cell activation device 82 Anode-side gas supply device 83. Voltage scanning circuit 84 Cathode-side gas supply device GH fuel gas Gc low oxygen gas Pt platinum

Claims

1. A fuel cell activation device for activating a fuel cell, which comprises, in order from one side, an anode layer, an electrolyte membrane, and a cathode layer, wherein the anode layer and the cathode layer contain platinum as a catalyst, an anode-side gas supply device configured to supply fuel gas, which contains hydrogen, to the anode layer, A cathode-side gas supply device configured to supply a low-oxygen gas, which has a lower oxygen concentration than air, to the cathode layer, A potential scanning circuit configured to control the potential of a fuel cell is provided, The anode-side gas supply device supplies the fuel gas to the anode layer, and the cathode-side gas supply device supplies the low-oxygen gas to the cathode layer while maintaining a constant flow rate without periodically changing it, and the potential of the cathode layer is controlled by the potential scanning circuit, thereby generating a proton pump. The hydrogen ions that have moved from the anode layer to the cathode layer by the proton pump combine with oxygen in the low-oxygen gas to generate water, which washes away deposits attached to the platinum and activates the fuel cell cell. Fuel cell activation device.

2. The cathode-side gas supply device supplies air to the cathode layer and also supplies nitrogen to the cathode layer while maintaining a constant flow rate without periodically changing it, thereby supplying the hypoxic gas to the cathode layer while maintaining a constant flow rate without periodically changing it. The fuel cell activation device according to claim 1.

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