Fuel cell activation device

Abstract

To efficiently activate a fuel battery cell.SOLUTION: An anode layer 20 and a cathode layer 40 of a fuel battery cell contain platinum as a catalyst. A fuel battery activation apparatus comprises a potential scan circuit 83, anode-side and cathode-side gas supply devices 82 and 84, and a control device. The potential scan circuit 83 is capable of applying a voltage to a fuel battery cell 50. The anode-side gas supply device 82 is capable of supplying a fuel gas as a gas, which contains hydrogen, to the anode layer 20. The cathode-side gas supply device 84 is capable of supplying an inert gas as a gas, which contains nitrogen and does not contain oxygen, to the cathode layer 40. While making a potential of the cathode layer 40 negative by the potential scan circuit 83, the control device supplies the fuel gas to the anode layer 20 by the anode-side gas supply device 82 and supplies the inert gas to the cathode layer 40 by the cathode-side gas supply device 84.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] Some fuel cells include an anode layer, an electrolyte membrane, and a cathode layer in order from one side. The anode layer and the cathode layer contain platinum as a catalyst. A fuel gas as a hydrogen-containing gas is supplied to the anode layer in a humidified state. On the other hand, an oxidizing gas as an oxygen-containing gas is supplied to the cathode layer in a humidified state.

[0003] When a load is connected to the fuel cell in the above state, hydrogen ions dissociated from hydrogen molecules in the fuel gas pass through the electrolyte membrane and move to the cathode layer, and combine with oxygen atoms and electrons dissociated from oxygen molecules in the oxidizing gas to form water molecules. Power generation is performed by the above series of processes.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In such fuel cells, the performance immediately after manufacture is often insufficient. The reasons include insufficient wetting of the ionomer in the anode-side catalyst layer, electrolyte membrane, and cathode-side catalyst layer, and the adhesion of deposits to platinum. Therefore, it is necessary to activate each fuel cell before shipping the fuel cell stack. As methods for such activation, there are the following power generation methods and non-power generation methods.

[0006] In this power generation method, fuel gas is supplied to the anode layer and oxidizing gas to the cathode layer, both humidified, and power is generated by connecting a load. By controlling the current during power generation, the potential is repeatedly swept, and the ion flow and generated water associated with the power generation wash away deposits attached to the platinum, thereby activating the fuel cell. Furthermore, at this time, moisture in the fuel gas and oxidizing gas, as well as water generated by power generation, is supplied to the anode layer, electrolyte membrane, and cathode layer, wetting the cell and further activating the fuel cell.

[0007] On the other hand, in the non-power generation method, humidified fuel gas is supplied to the anode layer, while humidified inert gas such as nitrogen (which does not contain oxygen) is supplied to the cathode layer, and the potential is controlled using an external device. With this non-power generation method, since oxidizing gas is not supplied to the cathode layer, the output of the fuel cell can be suppressed compared to the power generation method. On the other hand, since fuel gas is supplied to the anode layer, moisture moves along with the movement of hydrogen ions by the proton pump, wetting the cell. Therefore, with the non-power generation method, it is possible to activate the fuel cell by generating a proton pump while suppressing the output of the fuel cell.

[0008] However, compared to power generation methods, non-power generation methods can reduce equipment costs by limiting output, but simply implementing them requires time for activation and cannot activate fuel cell cells very efficiently.

[0009] This invention has been made in view of the above circumstances, and aims to efficiently activate fuel cell cells by a non-power generation method. [Means for solving the problem]

[0010] The inventors of this invention discovered that fuel cell cells can be efficiently activated by forcibly lowering the potential of the cathode layer during proton pump operation, leading to the present invention.

[0011] The fuel cell activation device of the present invention is A fuel cell is activated, comprising, in order from one side, an anode layer, an electrolyte membrane, and a cathode layer, with the anode layer and the cathode layer containing platinum as a catalyst.

[0012] The fuel cell activation device is A potential scanning circuit configured to apply voltage to the fuel cell, 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 an inert gas, which contains nitrogen but does not contain oxygen, to the cathode layer, A control device that controls the potential scanning circuit, the anode-side gas supply device, and the cathode-side gas supply device, It is equipped with.

[0013] The control device lowers the potential of the cathode layer compared to the case where the potential of the cathode layer is not negative by making the potential of the cathode layer negative with respect to the anode layer using the potential scanning circuit, while supplying the fuel gas to the anode layer by the anode-side gas supply device and supplying the inert gas to the cathode layer by the cathode-side gas supply device. [Effects of the Invention]

[0014] According to the present invention, the potential of the cathode layer is forcibly lowered by making the potential of the cathode layer negative relative to the anode layer using a potential scanning circuit. As a result, the platinum in the cathode layer becomes negatively charged, making it easier for a repulsive force to be generated between the platinum and the deposits, and making it easier for the deposits to delaminate from the platinum.

[0015] In this state, supplying fuel gas to the anode layer and inert gas to the cathode layer generates a proton pump. The water accompanying the ion flow associated with this proton pump washes away any deposits suspended from the platinum. As a result, the fuel cell cell can be activated efficiently.

[0016] As described above, according to this configuration, when the proton pump is operating, the fuel cell can be efficiently activated by making the potential of the cathode layer negative with respect to the anode layer.

Brief Description of the Drawings

[0017] [Figure 1] It is a schematic diagram showing a fuel cell activation device according to the first embodiment. [Figure 2] It is a schematic diagram showing the state during activation of a fuel cell by a fuel cell activation device. [Figure 3] It is a graph showing the transition of the potential of the representative part. [Figure 4] It is a schematic diagram showing the state during power generation by a fuel cell.

Modes 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.

[0021] During power generation, the anode layer 20 and the cathode layer 40 are electrically connected via a circuit 60c that includes the power supply target 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." Note that the oxidizing gas Go referred to here is air, which contains nitrogen and oxygen. During power generation, humidified fuel gas Gh is supplied to the anode-side gas diffusion layer 22, and humidified oxidizing gas Go is supplied to the cathode-side gas diffusion layer 42.

[0022] Hydrogen molecules H2 in the fuel gas Gh in the anode-side gas diffusion layer 22 flow into the anode-side catalyst layer 25, along with hydrogen ions H + It dissociates into electrons e. Platinum Pt acts as a catalyst in this reaction. Hydrogen ions H in the anode 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 due to insufficient wetting of the ionomer in the anode-side catalyst layer 25, electrolyte membrane 30, and cathode-side catalyst layer 45, as well as the presence of deposits d on the platinum Pt. For these reasons, each fuel cell 50 needs to be activated before the fuel cell stack 50s is shipped. The device for this activation is the fuel cell activation device 80 shown in Figure 1.

[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 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.

[0029] Hereinafter, gases that do not contain oxygen will be referred to as "inert gas Gn". Specifically, in this embodiment, inert gas Gn is nitrogen N2. The cathode-side gas supply device 84 is configured to supply inert gas Gn, humidified by the humidifier 84w, to the cathode-side gas diffusion layer 42. The control device 88 controls the flow rate and pressure of the inert gas Gn supplied to the cathode layer 40 by controlling the cathode-side gas supply device 84.

[0030] The potential scanning circuit 83 includes a potentiostat and the like. The electrodes of the anode layer 20 are electrically connected to the electrodes of the cathode layer 40 via a circuit 83c that includes the potential scanning circuit 83. The potential scanning circuit 83 is configured to allow voltage to be applied to the anode layer 20 and the cathode layer 40 from outside the fuel cell cell 50. Specifically, the potential scanning circuit 83 controls the potential of the cathode layer 40 relative to the anode layer 20 by, for example, applying a voltage to the cathode layer 40 relative to the anode layer 20.

[0031] Hereinafter, the potential at a predetermined location in the cathode layer 40 relative to the anode layer 20 will be referred to as the "representative potential Vr". Furthermore, the representative potential Vr when no voltage is applied will be referred to as the "representative natural potential VrN". Furthermore, the representative potential Vr when a voltage is applied will be referred to as the "representative forced potential VrF".

[0032] In this state, the control device 88 lowers the potential of the cathode layer 40 compared to when the voltage is not applied by turning on the voltage application by the potential scanning circuit 83. Specifically, when the voltage application is turned on, as shown in Figure 3, the representative potential Vr drops from the representative natural potential VrN to the representative forced potential VrF. The representative natural potential VrN is, for example, within the range of 0.05V or more and 0.20V or less.

[0033] Some of the deposits d that adhere to platinum Pt are negatively charged. By forcing the potential of the cathode layer 40 to become negative using the potential scanning circuit 83, the platinum Pt in the cathode layer 40 becomes more likely to become negatively charged. As a result, the adsorption force between the platinum Pt and the deposits d weakens, making it easier for the deposits d to detach from the platinum Pt.

[0034] The control device 88 controls the system as follows: The anode-side gas supply device 82, shown in Figure 2, humidifies the fuel gas Gh and supplies it to the anode-side gas diffusion layer 22, while the cathode-side gas supply device 84 humidifies the inert gas Gn and supplies it to the cathode-side gas diffusion layer 42.

[0035] This generates a proton pump. Specifically, hydrogen molecules H2 in the fuel gas Gh in the anode gas diffusion layer 22 become hydrogen ions H in the anode catalyst layer 25. + The reaction dissociates and flows into the anode-side catalyst layer 25, while electrons e flow into the circuit 83c. Platinum Pt acts as the catalyst for this reaction. Hydrogen ions H generated in 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.

[0036] Hydrogen ions H that have moved to the cathode-side catalyst layer 45 + The electrons e from circuit 83c combine to form hydrogen molecules H2. These hydrogen molecules H2 then diffuse into the cathode-side gas diffusion layer 42. Hydrogen ions H2 are then produced by the proton pump as described above. + As the reactants move, water (H2O) also moves, wetting the cell. This reduces the resistance to the movement of the reactants, and the fuel cell cell 50 becomes activated.

[0037] At this time, hydrogen ions (H) are produced by the proton pump. + The accompanying water H2O washes away the deposits d suspended from the platinum Pt due to the aforementioned negative potential. As a result, in addition to the activation of the fuel cell cell 50 by the aforementioned cell wetting, the fuel cell cell 50 is further activated by the increase in the effective catalyst surface area of ​​the platinum Pt.

[0038] The configuration and effects of this embodiment are summarized below.

[0039] Some deposits d that adhere to platinum Pt are negatively charged. In this embodiment, however, the potential scanning circuit 83 shown in Figure 2 applies a voltage to the anode layer 20 such that the potential of the cathode layer 40 becomes negative, thereby forcibly lowering the potential of the cathode layer 40. As a result, the platinum Pt on the cathode layer 40 becomes more likely to become negatively charged. Consequently, the adsorption force between the platinum Pt and the deposits d is weakened, making it easier for the deposits d to detach from the platinum Pt.

[0040] In this state, as shown in Figure 2, a proton pump is generated by supplying fuel gas Gh to the anode layer 20 and non-oxidizing gas Gn to the cathode layer. The water that moves along with the hydrogen ions associated with this proton pump efficiently washes away the deposits d whose adsorption force to platinum Pt has decreased due to the aforementioned negative potential. As a result, the fuel cell cell 50 can be efficiently activated.

[0041] As described above, according to this embodiment, the fuel cell cell 50 can be efficiently activated by making the potential of the cathode layer 40 negative relative to the anode layer 20 during proton pump operation.

[0042] Furthermore, the cathode-side gas diffusion layer 42 is supplied with inert gas Gn instead of oxidizing gas Go. As a result, the output of the fuel cell cell 50 can be reduced compared to when oxidizing gas Go is supplied. Therefore, high-cost equipment is not required. [Explanation of Symbols]

[0043] 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 88 Control device GH fuel gas Gn inert gas Pt platinum

Claims

[Claim 1] A fuel cell activation device for activating a fuel cell, comprising, 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, and negatively charged deposits are attached to the platinum, A potential scanning circuit configured to apply voltage to the fuel cell, 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 an inert gas, which contains nitrogen but does not contain oxygen, to the cathode layer, The system comprises a control device that controls the potential scanning circuit, the anode-side gas supply device, and the cathode-side gas supply device. The control device is By making the potential of the cathode layer negative relative to the anode layer using the potential scanning circuit, the platinum in the cathode layer is negatively charged, generating a repulsive force between the platinum and the deposit, causing the deposit to levitate away from the platinum, By supplying the fuel gas to the anode layer using the anode-side gas supply device and supplying the inert gas to the cathode layer using the cathode-side gas supply device, a proton pump is activated. The deposits floating from the platinum are washed away by the movement of water associated with the proton pump. Fuel cell activation device.

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