FUEL CELL ACTIVATION APPARATUS

Abstract

A fuel cell activation apparatus activates fuel cells. The fuel cells include, in order from one side, 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 apparatus includes an anode-side gas supply device, a cathode-side gas supply device, and a potential scanning circuit. The fuel cell activation apparatus activates the fuel cells by supplying a fuel gas to the anode layer by the anode-side gas supply device, supplying a low oxygen gas to the cathode layer by the cathode-side gas supply device, and controlling a cathode potential by the potential scanning circuit.

Claims

1. A fuel cell activation apparatus that activates a fuel cell, the fuel cell including, in order from one side, an anode layer, an electrolyte membrane, and a cathode layer, the anode layer and the cathode layer including platinum as a catalyst, the fuel cell activation apparatus comprising: an anode-side gas supply device that is configured to supply a fuel gas as a gas including hydrogen to the anode layer; a cathode-side gas supply device that is configured to supply a low oxygen gas as a gas having an oxygen concentration lower than that of air to the cathode layer; and a potential scanning circuit that is configured to control a potential of the fuel cell, wherein the anode-side gas supply device supplies the fuel gas to the anode layer, the cathode-side gas supply device supplies the low oxygen gas to the cathode layer, and the potential scanning circuit controls the potential of the cathode layer, such that the fuel cell is activated.

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

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 is a schematic view showing a fuel cell activation apparatus according to a first embodiment;

[0019] FIG. 2 is a schematic view showing a state during activation of a fuel cell by the fuel cell activation apparatus;

[0020] FIG. 3 is a schematic view showing a state during activation of a fuel cell according to a comparative embodiment; and

[0021] FIG. 4 is a schematic view showing a state during power generation by a fuel cell.

DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is in no way limited to the following embodiments, and can be appropriately modified and implemented within a range not departing from the gist of the present invention.

First Embodiment

[0023] The fuel cell activation apparatus 80 shown in FIG. 1 is installed for a fuel cell stack 50s. A plurality of fuel cells 50 are housed in the fuel cell stack 50s.

[0024] 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 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 than the cathode-side gas diffusion layer 42. Each of the anode-side gas diffusion layer 22 and the cathode-side gas diffusion layer 42 is mainly composed of a porous layer. The anode-side catalyst layer 25 and the cathode-side catalyst layer 45 contain platinum Pt as a catalyst.

[0025] During power generation, the anode layer 20 and the cathode layer 40 are electrically connected to each other via a circuit 60c including a power supply target 60. Hereinafter, the gas containing hydrogen is referred to as fuel gas Gh, and the gas containing oxygen is referred to as oxidizing gas Go. The oxidizing gas Go is air, and thus 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.

[0026] From the hydrogen molecules H.sub.2 in the fuel gas Gh in the anode-side gas diffusion layer 22, hydrogen ions H.sup.+ are dissociated and flow into the anode-side catalyst layer 25, and electrons e are dissociated and flow into the circuit 60c. In this reaction, platinum Pt serves as a catalyst. The hydrogen ions H.sup.+ flowing into the anode-side catalyst layer 25 pass through the electrolyte membrane 30 and migrate to the cathode-side catalyst layer 45. Hereinafter, such a phenomenon is referred to as proton pump. On the other hand, the electrons e flow from the anode layer 20 side toward the cathode layer 40 side in the circuit 60c.

[0027] The hydrogen ions H.sup.+ migrated to the cathode-side catalyst layer 45 are combined with the oxygen atoms O dissociated from the oxygen molecules O.sub.2 in the oxidizing gas Go in the cathode-side gas diffusion layer 42 and the electrons e from the circuit 60c to make water molecules H.sub.2O. The water molecules H.sub.2O diffuse into the cathode-side gas diffusion layer 42. Power generation is performed by the above-described series of flows.

[0028] In general, the performance of the fuel cell 50 described above immediately after production is insufficient. The reasons for this include insufficient humidification of the ionomers in the anode-side catalyst layer 25, the electrolyte membrane 30, and the cathode-side catalyst layer 45, and deposits adhering to the platinum Pt. Therefore, it is necessary to activate each fuel cell 50 before shipment of the fuel cell stack 50s shown in FIG. 1. The device for the activation is a fuel cell activation apparatus 80.

[0029] As shown in FIG. 1, the fuel cell activation apparatus 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 respectively include 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.

[0030] The voltmeter 87 is configured to be able to measure the output voltage of each fuel cell 50. The output voltage of each fuel cell 50 measured by the voltmeter 87 is inputted to the control device 88.

[0031] The cooling device 86 cools each fuel cell 50 by circulating a coolant between the fuel cell stack 50s and a radiator. The control device 88 controls the temperature of each fuel cell 50 to a temperature at which activation easily proceeds by the control of the cooling device 86.

[0032] As shown in FIG. 2, the electrode of the anode layer 20 and the electrode of the cathode layer 40 are electrically connected to each other via a circuit 83c including the potential scanning circuit 83. The potential scanning circuit 83 is configured to be able to control the potential of the fuel cell 50. Specifically, the fuel cell 50 applies an external power to activate each fuel cell 50 by controlling the potential of the cathode layer 40 relative to the anode layer 20.

[0033] 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 by the control of the anode-side gas supply device 82.

[0034] Hereinafter, a gas having an oxygen concentration lower than that of air is referred to as a low oxygen gas Gc. The cathode stoichiometric ratio in the low oxygen gas Gc is preferably 1.0 or less. The cathode stoichiometric ratio referred to herein is an optimum ratio of the amount of gas supplied to the anode layer 20 relative to the amount of gas supplied to the cathode layer 40.

[0035] The cathode-side gas supply device 84 is configured to be able to supply the low oxygen gas by supplying air together with the nitrogen gas N.sub.2, to the cathode-side gas diffusion layer 42. At this time, the low oxygen gas Gc can be humidified by supplying together with the water vapor generated by the humidifier 84w. 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 the control of the cathode-side gas supply device 84.

[0036] The control device 88 controls the anode-side gas supply device 82 shown in FIG. 2 to humidify the fuel gas Gh and supply the fuel gas Gh to the anode-side gas diffusion layer 22, controls the cathode-side gas supply device 84 to humidify the low oxygen gas Gc and supply the low oxygen gas Gc to the cathode-side gas diffusion layer 42, and controls the cathode potential by the potential scanning circuit 83. With such a configuration, a proton pump is generated.

[0037] Hereinafter, as shown in FIG. 3, a mode in which the cathode-side gas supply device 84 supplies not the low oxygen gas Gc but rather the nitrogen gas Gn to the cathode-side gas diffusion layer 42 during the proton pumping is referred to as a comparative embodiment. That is, in this comparative embodiment, the fuel cell 50 is activated by the non-power generation method.

[0038] In this comparative embodiment, from the hydrogen molecules H.sub.2 in the fuel gas Gh in the anode-side gas diffusion layer 22, the hydrogen ions H.sup.+ are dissociated and flow into the anode-side catalyst layer 25, and the electrons e are dissociated and flow into the circuit 83c. In this reaction, platinum Pt serves as a catalyst. The hydrogen ions H.sup.+ flowing into the anode-side catalyst layer 25 pass through the electrolyte membrane 30 and migrate to the cathode-side catalyst layer 45. On the other hand, the electrons e flow from the anode layer 20 side toward the cathode layer 40 side in the circuit 83c.

[0039] The hydrogen ions H.sup.+ migrated to the cathode-side catalyst layer 45 are combined with the electrons e from the circuit 83c to become hydrogen molecules H.sub.2. The hydrogen molecules H.sub.2 diffuse into the cathode-side gas diffusion layer 42. Due to the flow of ions accompanying the proton pump, moisture H.sub.2O migrates to humidify the fuel cell 50.

[0040] However, unlike the power generation method, since the water molecules H.sub.2O are not generated from the hydrogen ions H.sup.+ in the cathode layer 40, deposits d on the platinum Pt are not washed away by the generated water molecules H.sub.2O. In addition, the ionomers of the cathode-side gas diffusion layer 42 are not humidified by the generated water molecules H.sub.2O. Therefore, the activation effect of the fuel cell 50 is lower than that of the power generation method.

[0041] In this regard, in the present embodiment shown in FIG. 2, at the time of proton pump, the cathode-side gas supply device 84 supplies the low oxygen gas Gc rather than the nitrogen gas Gn to the cathode-side gas diffusion layer 42.

[0042] Also in the present embodiment, from the hydrogen molecules H.sub.2 in the fuel gas Gh in the anode-side gas diffusion layer 22, the hydrogen ions H.sup.+ are dissociated and flow into the anode-side catalyst layer 25, and the electrons e are dissociated and flow into the circuit 83c. The hydrogen ions H.sup.+ flowing into the anode-side catalyst layer 25 pass through the electrolyte membrane 30 and migrate to the cathode-side catalyst layer 45. On the other hand, the electrons e flow from the anode layer 20 side toward the cathode layer 40 side in the circuit 83c. The processing up to this point is the same as that in the above-described comparative embodiment.

[0043] The hydrogen ions H.sup.+ migrated to the cathode-side catalyst layer 45 are combined with the oxygen atoms O dissociated from the oxygen molecules O.sub.2 in the low oxygen gas Gc in the cathode-side gas diffusion layer 42 and the electrons e from the circuit 60c to make water molecules H.sub.2O. The deposits d attached to the platinum Pt are washed away by the water H.sub.2O. As a result, the effective catalyst surface area of platinum Pt increases, and the fuel cell 50 is activated.

[0044] Further, in the present embodiment, since the water molecules H.sub.2O are generated in the cathode layer 40, the ionomers of the cathode-side catalyst layer 45 are more easily humidified, and the fuel cell 50 is more easily activated.

[0045] The configuration and advantageous effects of the present embodiment will be summarized below.

[0046] According to the present embodiment, as shown in FIG. 2, the proton pump is generated by supplying the fuel gas Gh to the anode layer 20, and controlling the potential of the cathode layer 40. The hydrogen ions H.sup.+ migrated to the cathode layer 40 by the proton pump combine with the oxygen O.sub.2 in the low oxygen gas Gc to generate water H.sub.2O. The water H.sub.2O washes the deposits adhering to the platinum Pt in the cathode layer 40. In addition, the fuel cell 50 is humidified by the generated water H.sub.2O. This makes it possible to achieve a higher activation effect than in the comparative embodiment in which the non-power generation method is performed.

[0047] At this time, since the low oxygen gas Gc is supplied to the cathode layer 40, the stoichiometric ratio becomes lower than that in the case where air is supplied. By lowering the stoichiometric ratio in this way, it is possible to suppress the supply amount of the fuel gas Gh, and it is possible to suppress the output of the fuel cell 50. As a result, it is possible to reduce the size of the main body of the fuel cell activation apparatus 80, and it is possible to reduce the cost as compared with the case where air is supplied to the cathode layer 40, that is, as compared with the power generation method.

[0048] As described above, according to the present embodiment, it is possible to realize a higher activation effect than that of the non-power generation method at a cost lower than that of the power generation method.

[0049] Further, it is possible for the cathode-side gas supply device 84 to supply the low oxygen gas Gc to the cathode layer 40 easily and inexpensively by supplying air and nitrogen N.sub.2 to the cathode layer 40.

Other Embodiments

[0050] The embodiment described above can be modified as follows, for example. The potential scanning circuit 83 shown in FIG. 2 may be configured to be able to apply a negative voltage to the cathode layer 40 with respect to the anode potential. Then, the control device 88 may make the potential of the cathode layer 40 negative by the potential scanning circuit 83 at the time of proton pump. In this case, the platinum Pt of the anode layer 20 and the cathode layer 40 is easily negatively charged. Therefore, a repulsive force is likely to be generated between the platinum Pt and the deposits d. This is because the deposits d adhering to the platinum Pt are often negatively charged. As a result, the deposits d easily float from the platinum Pt, and the deposits d is more easily washed away from the platinum Pt.

EXPLANATION OF REFERENCE NUMERALS

[0051] 20 Anode Layer [0052] 30 Electrolyte Membrane [0053] 40 Cathode Layer [0054] 50 Fuel Cell [0055] 80 Fuel Cell Activation Apparatus [0056] 82 Anode-side Gas Supply Device [0057] 83 Voltage Scanning Circuit [0058] 84 Cathode-side Gas Supply Device [0059] Gh Fuel Gas [0060] Gc Low Oxygen Gas [0061] Pt Platinum