JP2012028115A - Fuel battery system, and operation method of fuel battery system - Google Patents

Abstract

An object of the present invention is to provide a fuel cell system capable of suppressing deterioration of carbon having low crystallinity when the operation of the fuel cell system is stopped.
A fuel cell having a first cell block and a second cell block, a fuel gas supply device, an oxidant gas supply device, an oxidant gas supply blocking mechanism, and a controller. The first cell block 51 and the second cell block 52 are electrically connected in series, and the crystallinity of the second carbon powder contained in the second cell block 52 is the first contained in the first cell block 51. The controller 110 lowers the crystallinity of the carbon powder and causes the oxidant gas supply cut-off mechanism 104 to cut off the supply of the oxidant gas to the second cell block 52 to perform deterioration-suppressing power generation, and then the fuel cell 101. And a fuel cell system for stopping the fuel gas supply device 102.
[Selection] Figure 2

Description

  The present invention relates to a fuel cell system and a method for operating the fuel cell system, and more particularly to a structure of a fuel cell having two or more cell stacks.

  A polymer electrolyte fuel cell (hereinafter referred to as PEFC (Polymer Electrolyte Fuel Cell)) reforms a raw material gas such as city gas, and electrochemically converts a fuel gas containing hydrogen and an oxidant gas containing oxygen such as air. By reacting, electricity and heat are generated simultaneously. A single cell (cell) of PEFC is composed of an electrolyte layer and a pair of gas diffusion electrodes, MEA (Membrane-Electrode-Assembly: electrolyte layer-electrode laminate), gasket, conductive plate separator, have. The main surface that contacts the gas diffusion electrode of the separator is provided with a groove-like gas flow path for flowing fuel gas or oxidant gas (these are called reaction gases), and the main surface that contacts the gas diffusion electrode The main surface on the opposite side is provided with a groove-like cooling medium flow path through which a cooling medium for recovering the generated heat and cooling the inside of the cell flows. The MEA having a gasket disposed at the peripheral edge is sandwiched between a pair of separators to form a cell. The cell stack is formed by stacking a plurality of cells, sandwiching both ends of the stacked cells with end plates, and fastening the end plates and the cells with a fastener.

  When such a PEFC is used in a household fuel cell, a device has been devised to improve the energy utilization efficiency by collecting the generated heat and using it for domestic hot water supply. Conventionally, in a domestic fuel cell, the temperature of hot water used for hot water supply was around 60 ° C. However, considering the downsizing of a hot water tank and application to floor heating, hot water having a higher temperature can be used. It has been demanded. In order to generate such hot water, it is necessary to increase the temperature of the cooling medium at the cell stack outlet.

  In addition, when PEFC is used for an automobile fuel cell, a large amount of heat is generated because it is necessary to generate a higher output as compared with a household fuel cell. Therefore, in order to efficiently cool the cell stack in a limited mounting space, it is necessary to take a large temperature difference between the cooling medium and the outside air. Therefore, also in the fuel cell for automobiles, it is required to make the temperature of the cooling medium at the cell stack outlet as high as possible.

  However, in order to increase the temperature of the cooling medium at the outlet of the fuel cell stack, it is necessary to raise the operating temperature of the cell stack. The electrolyte contained in the layer is dried, resulting in a problem that ion conductivity is lowered and power generation efficiency is lowered. In order to increase the relative humidity around the MEA, it is effective to increase the humidification temperature of the reaction gas. For this purpose, it is necessary to improve the performance of the humidifier, which increases the cost and size of the fuel cell system. Disadvantage that leads to

  As a result of intensive studies by the present inventors on such problems, even when the relative humidity around the MEA is reduced by increasing the water content of the carbon support used in the cathode catalyst layer, relatively high power generation is possible. It has been found that efficiency can be obtained.

  By the way, carbon having a large water content often has low crystallinity and deteriorates by being exposed to a high potential when the fuel cell system is stopped, so that there is a problem that sufficient durability cannot be ensured. In response to such a problem of carbon deterioration when the fuel cell is stopped, when the fuel cell is stopped, first, the supply of oxygen is stopped, and after the oxygen partial pressure reaches a predetermined value, the supply of hydrogen is stopped. A method of operating a polymer electrolyte fuel cell power generator is disclosed (see, for example, Patent Document 1). The operation method of the polymer electrolyte fuel cell power generator disclosed in Patent Document 1 is a constituent member of a polymer electrolyte fuel cell by suppressing the oxygen concentration remaining in the cathode after stopping the power generation operation of the fuel cell. Corrosion can be suppressed.

Special Table 2000-512069

  However, in the operation method of the polymer electrolyte fuel cell power generator disclosed in Patent Document 1 above, residual oxygen cannot be completely consumed. Therefore, when carbon with low crystallinity is used for the catalyst layer, However, there is still room for improvement in that catalyst deterioration cannot be sufficiently prevented and durability cannot be sufficiently secured.

  The present invention has been made in view of the above problems, and provides a fuel cell system and a fuel cell that exhibit high performance and achieve high durability even under operating conditions in which the relative humidity around the MEA tends to decrease. It aims at providing the operation method of a system.

  In order to solve the above-described conventional problems, a fuel cell system according to the present invention includes a first cell block in which cells having an anode, a cathode, and an electrolyte layer sandwiched between the anode and the cathode are stacked. 1st cell block group which has 1 or more and anode, 2nd cell block group which has 1 or more 2nd cell block formed by laminating | stacking the cell which has an anode, a cathode, and the electrolyte layer clamped by the said anode and said cathode A fuel cell, a fuel gas supplier for supplying fuel gas to the first cell block group and the second cell block group of the fuel cell via a fuel gas supply path, and the first cell of the fuel cell An oxidant gas supply device for supplying an oxidant gas to the block group and the second cell block group via an oxidant gas supply path; and a second cell of the fuel cell. An oxidant gas supply shut-off mechanism configured to shut off the supply of the oxidant gas to the block group, and a controller, wherein the first cell block group and the second cell block group are electrically The cathode of the first cell block group includes a first cathode catalyst layer having a first catalyst support including an electrode catalyst and a first carbon powder supporting the electrode catalyst, and The cathode of the two-cell block group includes a second cathode catalyst layer having an electrode catalyst and a second catalyst support including a first carbon powder supporting the electrode catalyst, and the crystallinity of the second carbon powder is Lower than the crystallinity of the first carbon powder, the controller activates the fuel gas supply device and the oxidant gas supply device, and moves to the second cell block group by the oxidant gas supply cutoff mechanism. Before To cut off the supply of oxidant gas performs deterioration suppressing power generation, then, stopping the fuel gas supply unit and the oxidizing gas supply device.

  Thereby, when the fuel cell system is stopped, the oxygen concentration remaining at the cathode of the second cell block group can be kept low, and deterioration of carbon having low crystallinity can be suppressed. On the other hand, since the highly crystalline carbon is used for the first cell block group, there is no risk of significant deterioration even if no special treatment is performed at the time of stopping. Furthermore, when the fuel cell system of the present invention is operated under low humidification conditions, high power generation performance can be exhibited by the second cell block. Therefore, even under low humidification conditions, high battery performance can be exhibited and high durability can be realized.

In the fuel cell system according to the present invention, the first catalyst carrier has a G-band peak half-width of 60 cm ⁻¹ or less, and the second catalyst carrier has a G-band peak half-width of 60 cm ⁻¹ . May be larger.

  In the fuel cell system according to the present invention, the moisture content of the second catalyst carrier may be greater than the moisture content of the first catalyst carrier.

In the fuel cell system according to the present invention, the water content of the first catalyst carrier under the condition of 80 ° C. and 90% RH saturated steam is 0.31 g-H ₂ O / g-C or less, The water content of the two-catalyst carrier may be greater than 0.31 g-H ₂ O / g-C.

  Further, in the fuel cell system according to the present invention, the controller causes the relative humidity of the oxidant gas flowing through the second cell block group of the fuel cell to flow through the first cell block group. The power generation of the fuel cell may be controlled to be lower than the relative humidity of the oxidant gas.

  In the fuel cell system according to the present invention, the controller may stop the fuel gas supplier and the oxidant gas supplier when the cathode potential of the second cell block group becomes lower than the anode potential. Good.

  The fuel cell system according to the present invention further includes a voltage detector that detects a voltage of the second cell block group, and the controller supplies the fuel gas when the voltage detected by the voltage detector is inverted. And the oxidant gas supply device may be stopped.

  Further, in the fuel cell system according to the present invention, the second cell block group includes a second cell through which the oxidant gas flows so as to pass through each cell block and to divert each cell of each cell block. A block internal oxidant gas flow path is provided, the fuel cell system further includes a pressure detector for detecting a pressure of the second cell block internal oxidant gas flow path, and the controller includes the pressure detector. When the detected pressure changes from a decreasing tendency to an increasing tendency, the fuel gas supply device and the oxidant gas supply device may be stopped.

  The fuel cell system according to the present invention further includes a cooling medium supplier that supplies a cooling medium to the first cell block group and the second cell block group of the fuel cell via a cooling medium supply path, and the control is performed. A dew point of the fuel gas and / or the oxidant gas flowing through the first cell block group and the second cell block group of the fuel cell is determined by the first cell block group of the fuel cell and the You may control so that it may become lower than the temperature of the said cooling medium which flows through a 2nd cell block group.

  Furthermore, in the fuel cell system according to the present invention, the first cell that passes through the first cell block and allows the cooling medium to flow through the cells of each cell block is divided into the first cell block. A block internal cooling medium flow path is provided, and the second cell block passes through the second cell block and allows the cooling medium to flow through the cells of each cell block. An internal cooling medium flow path may be provided, and the first cell block internal cooling medium flow path and the second cell block internal cooling medium flow path may be connected in series by a cooling medium connection path.

  In the fuel cell system operating method according to the present invention, the fuel cell system includes a first cell block in which cells each including an anode, a cathode, and an electrolyte layer sandwiched between the anode and the cathode are stacked. A fuel cell having a group and a second cell block group, a fuel gas supplier for supplying fuel gas to the first cell block group and the second cell block group of the fuel cell via a fuel gas supply path, and An oxidant gas supply device that supplies an oxidant gas to the first cell block group and the second cell block group of the fuel cell via an oxidant gas supply path, and the oxidation of the fuel cell to the second cell block An oxidant gas supply shut-off mechanism configured to shut off the supply of the agent gas, and the first cell block group and the second cell block group are electrically connected in series. And the cathode of the first cell block has a first cathode catalyst layer having a first catalyst support including an electrode catalyst and a first carbon powder supporting the electrode catalyst, and the cathode of the second cell block. The cathode has a second cathode catalyst layer having an electrode catalyst and a second catalyst support including the first carbon powder supporting the electrode catalyst, and the crystallinity of the second carbon powder is the crystal of the first carbon powder. The oxidant gas supply shut-off mechanism cuts off the supply of the oxidant gas to the second cell block group to perform deterioration-suppressing power generation, and then the fuel gas supply unit and the oxidant gas Stop the feeder.

  Thereby, when the fuel cell system is stopped, the oxygen concentration remaining at the cathode of the second cell block group can be kept low, and deterioration of carbon having low crystallinity can be suppressed. Further, even under low humidification conditions, high battery performance can be exhibited and high durability can be realized.

  According to the fuel cell system and the operation method of the fuel cell system of the present invention, it is possible to suppress deterioration of carbon having low crystallinity when the fuel cell system is stopped. Moreover, in the fuel cell system and the fuel cell system operation method of the present invention, it is possible to achieve high battery performance and high durability even when operated under low humidification conditions.

FIG. 1 is a schematic diagram showing a schematic configuration of a fuel cell system according to Embodiment 1 of the present invention. FIG. 2 is a schematic diagram showing a schematic configuration of the fuel cell system according to Embodiment 1 of the present invention. FIG. 3 is a perspective view schematically showing a schematic configuration of the second cell block of the fuel cell shown in FIG. 1. FIG. 4 is a cross-sectional view schematically showing a schematic configuration of the second cell of the second cell block shown in FIG. FIG. 5 is a flowchart schematically showing a stop operation of the fuel cell system according to the first embodiment. FIG. 6 is a schematic diagram showing a schematic configuration of a fuel cell system of Modification 1 of the fuel cell system according to Embodiment 1. In FIG. FIG. 7 is a schematic diagram showing a schematic configuration of a fuel cell system of Modification 2 of the fuel cell system according to Embodiment 1. In FIG. FIG. 8 is a schematic diagram showing a schematic configuration of a fuel cell system of Modification 3 of the fuel cell system according to Embodiment 1. In FIG. FIG. 9 is a schematic diagram showing a schematic configuration of a fuel cell system according to Embodiment 2 of the present invention. FIG. 10 is a flowchart schematically showing a stop operation of the fuel cell system according to the second embodiment. FIG. 11 is a table showing the results of Evaluation Test 1. FIG. 12 is a graph showing the results of evaluation test 2.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted. Further, in all the drawings, only components necessary for explaining the present invention are extracted and illustrated, and other components are not illustrated. Furthermore, the present invention is not limited to the following embodiment.

(Embodiment 1)
A fuel cell system according to Embodiment 1 of the present invention includes a fuel cell having a first cell block group and a second cell block group, a fuel gas supply device, an oxidant gas supply device, and an oxidant gas supply cutoff mechanism. And the controller, the crystallinity of the second carbon powder contained in the cathode of the second cell block group is lower than the crystallinity of the first carbon powder contained in the cathode of the first cell block group, Exemplified is a mode in which the generator cuts off the supply of the oxidant gas to the second cell block group by the oxidant gas supply cut-off mechanism to perform deterioration-suppressing power generation and then stops the fuel gas supply unit and the oxidant gas supply unit To do.

[Configuration of fuel cell system]
1 and 2 are schematic diagrams showing a schematic configuration of a fuel cell system according to Embodiment 1 of the present invention. 1 shows the flow of the reaction gas and the cooling medium during the power generation operation of the fuel cell system, and FIG. 2 shows the flow of the reaction gas and the cooling medium during the deterioration suppressing power generation operation of the fuel cell system. Yes.

  As shown in FIG. 1, a fuel cell system 100 according to Embodiment 1 of the present invention includes a fuel cell 101 having a first cell block 51 and a second cell block 52, a fuel gas supplier 102, and an oxidant gas. A supply device 103, an oxidant gas supply cutoff mechanism 104, and a controller 110 are provided. Then, the controller 110 cuts off the supply of the oxidant gas to the second cell block 52 by the oxidant gas supply cut-off mechanism 104 to perform deterioration-suppressing power generation, and then the fuel gas supply unit 102 and the oxidant gas supply unit 103 is stopped.

  The fuel cell supplier 102 is connected to the second cell block 52 of the fuel cell 101 via the fuel gas supply path 132 (more precisely, the inlet of the second cell block internal fuel gas flow path 52A). The fuel gas supply unit 102 may be in any form as long as the fuel gas (hydrogen gas) can be supplied to the fuel cell 101 while adjusting its flow rate and humidification amount. The first embodiment includes a device configured to supply hydrogen gas such as a hydrogen generator, a hydrogen cylinder, or a hydrogen storage alloy, a humidifier, and a flow rate regulator (whichever (Not shown).

  The hydrogen generator is configured to generate a fuel gas from a raw material gas (for example, methane gas or propane gas) and water. Further, the humidifier may be of any form as long as the fuel gas from the hydrogen generator or the like can be humidified. For example, when the cooling medium is water, the humidifier performs total heat exchange with the cooling medium. It may be a total heat exchanger, or a so-called humidifier that humidifies the fuel gas using water stored in a tank or the like as water vapor. The flow rate regulator may be constituted by, for example, a pump that can regulate the flow rate, a pump, and a flow rate regulating valve.

  The oxidant gas supply unit 103 is connected to the second cell block 52 of the fuel cell 101 (more precisely, the inlet of the oxidant gas flow path 52B inside the second cell block) via the oxidant gas supply path 133. ing. The oxidant gas supply unit 103 may be in any form as long as the oxidant gas (air) can be supplied to the fuel cell 101 while adjusting the flow rate and the humidification amount, for example. The first embodiment includes fans such as a fan and a blower, a humidifier, and a flow rate regulator (all not shown).

  The humidifier may be in any form as long as it can humidify the oxidant gas supplied from the fans. For example, when the cooling medium is water, the humidifier performs all heat exchange with the cooling medium. It may be a heat exchanger, or a so-called humidifier that humidifies the oxidant gas using water stored in a tank or the like as water vapor. The flow rate regulator may be constituted by, for example, a pump that can regulate the flow rate, a pump, and a flow rate regulating valve.

  The outlet of the second cell block internal fuel gas flow path 52A of the second cell block 52 is connected to the first cell block 51 (more precisely, the first cell block internal fuel gas flow path 51A via the fuel gas connection path 134). The entrance) is connected. A fuel gas discharge path 136 is connected to the outlet of the first cell block internal fuel gas flow path 51A. The outlet of the second cell block internal oxidant gas flow path 52B is connected to the first cell block 51 (more precisely, the inlet of the first cell block internal oxidant gas flow path 51B via the oxidant gas connection path 135). ) Is connected. An oxidant gas discharge path 137 is connected to the outlet of the first cell block internal oxidant gas flow path 51B.

  As a result, the appropriately humidified fuel gas flows from the fuel gas supply device 102 through the fuel gas supply path 132 and is supplied to the fuel cell 101 (more precisely, the second cell block 52). The agent gas flows from the oxidant gas supply device 103 through the oxidant gas supply path 133 and is supplied to the fuel cell 101 (more precisely, the second cell block 52).

  The fuel gas supplied to the second cell block 52 flows through the second cell block internal fuel gas flow path 52 </ b> A and is supplied to the first cell block 51 from the fuel gas connection path 134. The oxidant gas supplied to the second cell block 52 flows through the second cell block internal oxidant gas flow path 52 </ b> B and is supplied to the first cell block 51 from the oxidant gas connection path 135.

  The fuel gas supplied to the first cell block 51 flows through the first cell block internal fuel gas flow path 51A. The fuel gas that has not been used in the second cell block 52 and the first cell block 51 is discharged to the fuel gas discharge path 136. The oxidant gas supplied to the first cell block 51 flows through the first cell block internal oxidant gas flow path 51B. The oxidant gas that has not been used in the first cell block 51 and the second cell block 52 is discharged to the oxidant gas discharge path 137. The unused fuel gas may be discharged to the outside of the fuel cell system 100 (in the atmosphere) after being sufficiently diluted with an unused oxidant gas, for example. May be supplied to a combustor (not shown) of the hydrogen generator.

  In the middle of the oxidant gas supply path 133 and the oxidant gas connection path 135, the oxidant gas supply blocking mechanism 104 is disposed so as to straddle these paths. The oxidant gas supply blocking mechanism 104 is configured to block the supply of oxidant gas to the second cell block 52 of the fuel cell 101. Specifically, the oxidant gas supply cutoff mechanism 104 includes an oxidant gas supply switching unit 104A and an oxidant gas bypass path 104B. In the first embodiment, the oxidant gas supply switching unit 104A is configured by a three-way valve, and the oxidant gas supply destination (flow destination) flowing through the oxidant gas supply path 133 is the second cell. The block 52 and the oxidant gas bypass path 104B are configured to be switched. The upstream end of the oxidant gas bypass path 104B is connected to the oxidant gas supply switching unit 104A, and the downstream end is connected to the middle of the oxidant gas connection path 135.

  In addition, the fuel cell system 100 includes a cooling medium supplier 105. The coolant supply unit 105 is connected to the second cell block 52 of the fuel cell 101 (more precisely, the inlet of the second cell block coolant internal flow path 52C). The coolant supply unit 105 includes, for example, a tank that stores a coolant supplied from the outside, a coolant temperature controller, a pump, and a flow rate adjustment valve. Examples of the cooling medium temperature adjuster include a heat exchanger that exchanges heat with fuel gas, oxidant gas, and the like, a heater such as a heater that heats the cooling medium, and a cooler that cools the cooling medium. Moreover, as a cooling medium, antifreezing liquids, such as water and ethylene glycol, are mentioned, for example. In the first embodiment, the cooling medium supply unit 105 is configured by a tank, a pump, and a flow rate adjustment valve. However, the present invention is not limited to this, and the flow rate adjustment valve is provided when the pump can adjust the flow rate. It is good also as a structure which does not have.

  The outlet of the second cell block cooling medium internal flow path 52C of the second cell block 52 is connected to the first cell block 51 (more precisely, the first cell block cooling medium internal flow path 51C via a cooling medium connection flow path 139). Is connected). A cooling medium discharge path 140 is connected to the outlet of the first cell block cooling medium internal flow path 51C.

  Accordingly, the cooling medium adjusted to an appropriate temperature is supplied from the cooling medium supply unit 105 through the cooling medium supply path 138 to the second cell block 52. The cooling medium supplied to the second cell block 52 flows through the second cell block cooling medium internal flow path 52C and is supplied from the cooling medium connection flow path 139 to the first cell block 51. The cooling medium supplied to the first cell block 51 flows through the first cell block cooling medium internal flow path 51C, and is discharged out of the fuel cell system 100 from the cooling medium discharge path 140. In this way, the temperature of the fuel cell 101 is adjusted by the cooling medium supplier 105. In the first embodiment, the cooling medium is discharged from the fuel cell system 100. However, the present invention is not limited to this, and a cooling medium supply device 105 and the fuel cell 101 are circulated. May be.

  In addition, the second cell block 52 and the first cell block 51 of the fuel cell 101 are electrically connected by an electrical wiring 161. The second cell block 52 is provided with a voltage detector 106 that detects the voltage in the second cell block 52. The voltage detector 106 is configured to output the detected voltage of the second cell block 52 to the controller 110. Further, the fuel cell 101 is provided with a power regulator 107 for supplying power generated in the fuel cell 101 to an external power load. The power regulator 107 includes, for example, a converter that converts DC power generated by the fuel cell 101 into a DC voltage, and an inverter that converts DC power output from the converter into AC power. The power adjuster 107 adjusts the electric power extracted from the fuel cell 101 under the control of the controller 110.

  The controller 110 is configured by a computer such as a microcomputer, and is configured to control each device such as a power generation operation of the fuel cell system 100 by controlling each device of the fuel cell system 100. The controller 110 includes, for example, a CPU, an internal memory composed of a semiconductor memory, a communication unit, and a clock unit (all not shown) having a calendar function. Here, in the present invention, the controller means not only a single controller but also a controller group in which a plurality of controllers cooperate to execute control of the fuel cell system 100. For this reason, the controller 110 does not need to be composed of a single controller, and a plurality of controllers may be arranged in a distributed manner so as to control the fuel cell system 100 in cooperation with each other. .

  In the first embodiment, the second cell block internal fuel gas flow path 52A of the second cell block 52 and the first cell block internal fuel gas flow path 51A of the first cell block 51 are connected in series. However, the present invention is not limited to this, and a form in which the second cell block internal fuel gas flow path 52A and the first cell block internal fuel gas flow path 51A are connected in parallel may be employed. Here, that two flow paths are connected in series means that the downstream end (exit) of one flow path and the upstream end (inlet) of the other flow path are connected. In addition, two channels connected in parallel means that the upstream end (inlet) of one channel and the upstream end (inlet) of the other channel are connected.

  Similarly, the second cell block cooling medium internal flow path 52C of the second cell block 52 and the first cell block cooling medium internal flow path 51C of the first cell block 51 are connected in series. Without being limited thereto, a form in which the second cell block cooling medium internal flow path 52C and the first cell block cooling medium internal flow path 51C are connected in parallel may be employed. From the viewpoint of easily increasing the temperature of the cooling medium discharged from the fuel cell 101, the second cell block cooling medium internal flow path 52C and the first cell block cooling medium internal flow path 51C are connected in series. It is preferable to adopt.

[Configuration of fuel cell]
Next, the configuration of the second cell block 52 of the fuel cell 101 will be described with reference to FIG. FIG. 3 is a perspective view schematically showing a schematic configuration of the second cell block 52 of the fuel cell 101 shown in FIG. Since the basic configuration of the first cell block 51 is the same as that of the second cell block 52, detailed description thereof is omitted.

  As shown in FIG. 3, a cell laminate 70 in which the second cells 22 having a plate-like overall shape are laminated in the thickness direction thereof, end plates 61 and 62 disposed at both ends of the cell laminate 70, An end plate 61, a cell stack 70, and a fastener (not shown) that fastens the end plate 62 in the stacking direction of the second cells 22. A current collecting plate and an insulating plate are disposed between the end plate 61 and the cell stack 70 and between the end plate 62 and the cell stack 70, respectively, but are not shown.

  The cell stack 70 includes a fuel gas supply manifold 32, a fuel gas discharge manifold 34, an oxidant gas supply manifold 33, and an oxidant gas discharge manifold so as to penetrate in the stacking direction of the second cells 22 of the cell stack 70. 35, a cooling medium supply manifold 38, and a cooling medium discharge manifold 39 are provided. Note that the flow direction of the oxidant gas and the cooling medium in the stacking direction of the second cells 22 is preferably the same from the viewpoint of making the in-plane humidity distribution as small as possible.

  The fuel gas supply manifold 32, the fuel gas flow path 8 provided in the second cell 22 described later, and the fuel gas discharge manifold 34 constitute the second cell block internal fuel gas flow path 52A, and the oxidant gas supply manifold. 33, the oxidant gas flow path 9 provided in the second cell 22 and the oxidant gas discharge manifold 35 constitute a second cell block internal oxidant gas flow path 52B. In addition, the cooling medium supply manifold 38, the cooling medium flow path 10 provided in the second cell 22, and the cooling medium discharge manifold 39 constitute a second cell block cooling medium internal flow path 52C.

[Cell structure]
Next, the configuration of the first cell 21 constituting the first cell block 51 and the second cell 22 constituting the second cell block 52 will be described in detail with reference to FIG. Since the basic configuration of the first cell 21 and the second cell 22 is the same, only the difference between the first cell 21 and the second cell 22 will be described.

  4 is a cross-sectional view schematically showing a schematic configuration of the second cell 22 of the second cell block 52 shown in FIG. In FIG. 4, a part is omitted.

  As shown in FIG. 4, the second cell 22 includes an MEA (Membrane-Electrode-Assembly: membrane-electrode assembly) 5, a gasket 7, an anode separator 6A, and a cathode separator 6B.

  First, the MEA 5 will be described.

  The MEA 5 includes a polymer electrolyte membrane (electrolyte layer) 1 that selectively transports hydrogen ions, an anode electrode 4A, and a cathode electrode 4B. The polymer electrolyte membrane 1 has a substantially quadrangular (here, rectangular) shape, and an anode electrode 4A and a cathode are positioned on both sides of the polymer electrolyte membrane 1 so as to be located inward from the peripheral edge thereof. Electrodes 4B are provided respectively. Note that manifold holes (not shown) such as an oxidant gas discharge manifold hole are provided in the periphery of the polymer electrolyte membrane 1 so as to penetrate in the thickness direction.

  The anode electrode 4A is provided on one main surface of the polymer electrolyte membrane 1, and includes an electrode catalyst, a second carbon powder supporting the electrode catalyst, and a second catalyst support including a polymer electrolyte. The catalyst layer 2A and the anode gas diffusion layer 3A provided on the anode catalyst layer 2A and having both gas permeability and conductivity are provided. Similarly, the cathode electrode 4B is provided on the other main surface of the polymer electrolyte membrane 1, and includes an electrode catalyst, a second carbon powder supporting the electrode catalyst, and a second catalyst support including a polymer electrolyte, A cathode catalyst layer 2B, and a cathode gas diffusion layer 3B provided on the cathode catalyst layer 2B and having both gas permeability and conductivity.

The anode catalyst layer 2A and the cathode catalyst layer 2B may further include a water repellent material such as polytetrafluoroethylene, for example. The configurations of the anode catalyst layer 2A and the cathode catalyst layer 2B may be the same or different. The carbon powder used as the catalyst carrier preferably has a D-band peak half-value width in the range of 5 to 200 cm ⁻¹ by Raman spectroscopic measurement. The catalyst carrier has a water content of 0.01 to 10 g-H ₂ O / g-C measured using a moisture adsorption / desorption measuring device under conditions of 80 ° C. and 90% RH saturated steam. Is preferred. Here, the moisture content (g-H ₂ O / g-C) of the catalyst carrier is determined by measuring the catalyst carrier including the electrode catalyst and the carbon powder using a moisture adsorption / desorption measuring device, and the amount of moisture per carbon element. As converted.

  Moreover, metal particles can be used as the electrode catalyst. The metal particles are not particularly limited, and various metals can be used. From the viewpoint of electrode reaction activity, platinum, gold, silver, ruthenium, rhodium, palladium, osmium, iridium, chromium, iron, titanium, It is preferably at least one metal selected from the metal group consisting of manganese, cobalt, nickel, molybdenum, tungsten, aluminum, silicon, zinc and tin. Among these, platinum or an alloy of platinum and at least one metal selected from the above metal group is preferable, and an alloy of platinum and ruthenium is particularly preferable because the activity of the catalyst is stabilized in the anode catalyst layer 2A.

  By the way, the catalyst layer of the fuel cell 101 (refers to both the anode catalyst layer 2A and the cathode catalyst layer 2B) has a moisture content in order to exhibit high power generation efficiency even when the operating conditions are low humidification conditions. Larger is preferable. In general, carbon powder with high crystallinity often has a low water content, and conversely, carbon powder with low crystallinity often has a high water content. On the other hand, from the viewpoint of suppressing deterioration of the catalyst layer when the fuel cell system 100 is stopped, it is preferable to use carbon powder having high crystallinity.

  Therefore, in the present invention, as will be described later, the deterioration of the catalyst layer is suppressed by preventing the second cell block 52 from being exposed to a high potential when the fuel cell system 100 is stopped. The second carbon powder contained in the second catalyst carrier constituting the cathode catalyst layer 2B of the second cell 22 has a crystallinity of the first cell 21 so as to exhibit high power generation performance even under low humidification conditions. The cathode catalyst layer 2B is made of a material having a lower crystallinity than the first carbon powder contained in the first catalyst carrier. On the other hand, since the first cell block 51 may be exposed to a high potential when the operation of the fuel cell system 100 is stopped, the first cell block 51 is included in the first catalyst carrier constituting the cathode catalyst layer 2B of the first cell 21. Carbon powder with high crystallinity is used.

Specifically, from the viewpoint of enhancing the crystallinity of the first carbon powder, the first catalyst support preferably has a smaller D-band peak half-value width by Raman spectroscopic measurement, preferably 60 cm ⁻¹ or less. More preferably, it is 52 cm ⁻¹ or less. On the other hand, the second catalyst carrier preferably has a half-width of D-band peak by Raman spectroscopic measurement larger than 60 cm ⁻¹ from the viewpoint of exhibiting high power generation performance even under low humidification conditions. From the same viewpoint, the second catalyst carrier preferably has a higher moisture content than the first catalyst carrier, and preferably has a moisture content greater than 0.31 g-H ₂ O / g-C. Moreover, it is preferable that the water content of the first catalyst carrier is 0.31 g-H ₂ O / g-C or less.

  Next, other elements of the second cell 22 will be described.

  Around the anode electrode 4A and the cathode electrode 4B (more precisely, the anode gas diffusion layer 3A and the cathode gas diffusion layer 3B) of the MEA 5, a pair of fluorine rubber doughnut-shaped gaskets 7 with the polymer electrolyte membrane 1 interposed therebetween Is arranged. This prevents fuel gas and oxidant gas from leaking out of the battery, and prevents these gases from being mixed with each other in the second cell block 52. Note that a manifold hole (not shown) such as an oxidant gas discharge manifold hole made of a through hole in the thickness direction is provided at the peripheral edge of the gasket 7.

  In addition, a conductive anode separator 6A and a cathode separator 6B are disposed so as to sandwich the MEA 5 and the gasket 7. Thereby, MEA 5 is mechanically fixed, and when a plurality of second cells 22 are stacked in the thickness direction, MEA 5 is electrically connected. In addition, these separators 6A and 6B can use the metal excellent in heat conductivity and electroconductivity, graphite, or what mixed graphite and resin, for example, carbon powder and a binder (solvent). A mixture prepared by injection molding or a plate of titanium or stainless steel plated with gold can be used.

  On one main surface (hereinafter referred to as an inner surface) of the anode separator 6A that is in contact with the anode electrode 4A, a groove-like fuel gas flow path 8 is provided for allowing the fuel gas to flow therethrough. A groove-like cooling medium flow path 10 through which the cooling medium flows is provided on the surface (hereinafter referred to as an outer surface). Similarly, a groove-like oxidant gas flow path 9 through which an oxidant gas flows is provided on one main surface (hereinafter referred to as an inner surface) of the cathode separator 6B that is in contact with the cathode electrode 4B. The other main surface (hereinafter referred to as an outer surface) is provided with a groove-like cooling medium flow path 10 through which the cooling medium flows.

  The fuel gas flow path 8 and the oxidant gas flow path 9 may be provided so as to be a so-called counter flow, or may be provided so as to be a so-called parallel flow. Here, the counter flow has a part in which the oxidant gas and the fuel gas flow in parallel to each other when viewed from the thickness direction of the first cell 21 (or the second cell 22). It means that the directions of the overall flow from the upstream side to the downstream side of the oxidant gas and the fuel gas are opposite to each other (as a whole). In addition, the parallel flow has a part that flows so that the oxidant gas and the fuel gas are opposite to each other when viewed from the thickness direction of the first cell 21 (or the second cell 22). It means that the directions of the overall flow from the upstream side to the downstream side of the oxidant gas and the fuel gas coincide with each other.

  Thereby, fuel gas and oxidant gas are supplied to the anode electrode 4A and the cathode electrode 4B, respectively, and these gases react to generate electricity and heat. Further, the generated heat is recovered by passing a cooling medium such as cooling water through the cooling medium flow path 10.

[Operation of fuel cell system]
Next, the operation of the fuel cell system 100 according to Embodiment 1 will be described with reference to FIGS. FIG. 5 is a flowchart schematically showing a stop operation of the fuel cell system 100 according to the first embodiment.

  Here, the stop operation of the fuel cell system 100 will be described, and the operation operation (power generation operation) of the fuel cell system 100 according to Embodiment 1 is performed in the same manner as the operation operation of a general fuel cell system. Therefore, the following will be noted. During the power generation operation of the fuel cell system 100, the controller 110 uses the oxidant gas flowing through the second cell block internal oxidant gas flow path 52 </ b> B of the second cell block 52 in the first cell block 51. The fuel gas supply device 102, the oxidant gas supply device 103, and the cooling medium supply device 105 are controlled so that the relative humidity is lower than that of the oxidant gas flowing through the cell block internal oxidant gas flow path 51B. ing.

  Specifically, the flow rates of the fuel gas, the oxidant gas, and the cooling medium supplied from the fuel gas supply unit 102, the oxidant gas supply unit 103, and the cooling medium supply unit 105, and the humidification amounts of the fuel gas and the oxidant gas The oxidant gas flowing through the second cell block internal oxidant gas flow path 52B of the second cell block 52 is controlled by controlling the oxidant gas flow path inside the first cell block of the first cell block 51. The relative humidity can be made lower than that of the oxidant gas flowing through 51B.

  First, when the preset operation stop time of the fuel cell system 100 is reached or when the user operates the remote controller to instruct the operation stop of the fuel cell system 100, the controller 110 controls the fuel cell system 100. An operation stop command is output to each of the devices (step S101).

  Next, the controller 110 outputs an oxidant gas supply cutoff command to the second cell block 52 to the oxidant gas supply cutoff mechanism 104 (step S102). Thereby, the oxidant gas supply switching unit 104A of the oxidant gas supply cutoff mechanism 104 switches the supply destination of the oxidant gas from the second cell block 52 to the oxidant gas bypass path 104B. The fuel cell system 100 performs deterioration-suppressing power generation.

  Here, the deterioration-suppressing power generation refers to performing a power generation operation in a state where the supply of the oxidant gas to the second cell block 52 is shut off. During the deterioration-suppressing power generation, the first cell block 51 generates power. On the other hand, the oxidant gas is not supplied to the second cell block 52. Therefore, in the second cell block 52, the oxidant gas in the second cell block internal oxidant gas flow path 52B is consumed by the electrochemical reaction using the electric power generated in the first cell block 51. .

  Next, the controller 110 acquires the voltage detected by the voltage detector 106 (step S103). Next, the controller 110 determines whether or not the voltage acquired in step S103 is inverted (step S104). As described above, in the second cell block 52, the oxidant gas in the second cell block internal oxidant gas flow path 52B is consumed. When the oxidant gas remaining in the second cell block internal oxidant gas flow path 52B is sufficiently reduced (the oxidant gas in the second cell block 52 is almost completely consumed), the cathode electrode 4B. Then, since the hydrogen generation reaction occurs, the voltage of the second cell block 52 is inverted.

  That is, in the first embodiment, the state in which the potential of the cathode electrode 4B of the second cell block 52 is lower than the potential of the anode electrode 4A is detected by detecting the voltage of the second cell block 52. I have to. The inversion of the voltage of the second cell block 52 is such that the voltage detected by the voltage detector 106 is positive when the positive electrode of the voltage detector 106 is connected to the cathode electrode 4B of the second cell block 52. A negative value from the value indicates that the voltage has been reversed. Further, when the positive electrode of the voltage detector 106 is connected to the anode electrode 4A of the second cell block 52, it can be determined that the voltage is inverted when a positive value is shown from a negative value.

  If the voltage is not inverted (No in step S104), the controller 110 returns to step S103 and repeats step S103 and step S104 until the voltage is inverted. On the other hand, when the voltage is inverted (Yes in step S104), the controller 110 proceeds to step S105.

  In step S105, the controller 110 causes the power regulator 107 to stop supplying power to the external power load. Next, the controller 110 causes the fuel gas supply unit 102 and the oxidant gas supply unit 103 to stop supplying the fuel gas and the oxidant gas to the fuel cell 101 (step S106).

[Function and effect of fuel cell system]
In the fuel cell system 100 according to Embodiment 1 configured as described above, when the fuel cell system 100 is stopped, the supply of the oxidant gas to the second cell block 52 is shut off, and the first cell block 51 is also stopped. The oxidant gas remaining in the second cell block 52 can be more sufficiently reduced by continuing the supply of the oxidant gas. As described above, in the second cell block 52 using the second carbon powder having low crystallinity, the deterioration of the catalyst layer is sufficiently suppressed by sufficiently reducing the remaining oxidant gas. Can do. On the other hand, because the first carbon block 51 uses the first carbon powder with high crystallinity, even if the catalyst layer is exposed to a high potential when the fuel cell system 100 is stopped, the catalyst layer is deteriorated. Can be suppressed.

  Furthermore, in the fuel cell system 100 according to the first embodiment, by using the second carbon powder having low crystallinity for the second cell block 52, high power generation performance can be exhibited during power generation operation. When the reaction gas supplied to the fuel cell 101 is in a low humidification condition, high power generation performance can be exhibited.

  In the first embodiment, the controller 110 causes the dew point of the fuel gas and / or oxidant gas flowing through the fuel cell 101 to be lower than the temperature of the cooling medium flowing through the fuel cell 101. In other words, the coolant supply unit 105, the fuel gas supply unit 102, and / or the oxidant gas supply unit 103 may be controlled so that the fuel gas and / or the oxidant gas are in a low humidification condition.

  In the first embodiment, the oxidant gas supply cutoff mechanism 104 includes the oxidant gas supply switching unit 104A with a three-way valve. However, the present invention is not limited to this, and the oxidant gas supply path 133 is not limited to this. The oxidant gas supply switching unit 104A may be configured by an on-off valve provided in each of the part downstream of the part to which the bypass path 104B is connected and the oxidant gas bypass path 104B. Further, in order to more reliably shut off the supply of the oxidant gas to the second cell block 52, an opening / closing provided upstream of the portion of the oxidant gas connection path 135 to which the oxidant gas bypass path 104B is connected. The oxidant gas supply shut-off mechanism 104 may be configured by the valve, the oxidant gas supply switching unit 104A, and the oxidant gas bypass path 104B.

  Further, in the first embodiment, a mode is determined in which whether or not the potential of the cathode electrode 4B of the second cell block 52 is lower than the potential of the anode electrode 4A by the voltage detected by the voltage detector 106. However, the present invention is not limited to this. For example, after the supply of the oxidant gas to the second cell block 52 is shut off in advance by an experiment or the like, the potential of the cathode electrode 4B of the second cell block 52 becomes the anode electrode 4A. A time T that is lower than the potential is obtained, and when the time T passes, the power supply to the external power load is stopped and the fuel gas supply device 102 and the oxidant gas supply device 103 are stopped. May be.

[Modification 1]
Next, a modification of the fuel cell system 100 according to Embodiment 1 will be described.

  FIG. 6 is a schematic diagram showing a schematic configuration of a fuel cell system of Modification 1 of the fuel cell system according to Embodiment 1. In FIG. FIG. 6 shows the flow of the reaction gas and the cooling medium during the deterioration suppressing power generation operation of the fuel cell system.

  As shown in FIG. 6, the fuel cell system 100 according to the first modification has the same basic configuration as the fuel cell system 100 according to the first embodiment, but the first cell block 51 is more than the second cell block 52. Also differs in that it is arranged upstream. Therefore, the fuel gas supply device 102 is connected to the inlet of the first cell block internal fuel gas flow path 51 </ b> A via the fuel gas supply path 132. The inlet of the first cell block internal oxidant gas flow path 51 </ b> B is connected to the oxidant gas supply unit 103 via the oxidant gas supply path 133. An inlet of the first cell block cooling medium internal flow path 51 </ b> C is connected to the cooling medium supply unit 105 via a cooling medium supply path 138.

  The fuel gas connection path 134 connects the outlet of the first cell block internal fuel gas flow path 51A and the inlet of the second cell block internal fuel gas flow path 52A. The oxidant gas connection path 135 connects the outlet of the first cell block internal oxidant gas flow path 51B and the inlet of the second cell block internal oxidant gas flow path 52B. The cooling medium connection flow path 139 connects the outlet of the first cell block cooling medium internal flow path 51C and the inlet of the second cell block cooling medium internal flow path 52C.

  Further, a fuel gas discharge path 136 is connected to the outlet of the second cell block internal fuel gas flow path 52A. An oxidant gas discharge path 137 is connected to the outlet of the second cell block internal oxidant gas flow path 52B. A cooling medium discharge path 140 is connected to the outlet of the second cell block cooling medium internal flow path 52C.

  The oxidant gas supply blocking mechanism 104 is disposed so as to straddle the oxidant gas connection path 135 and the oxidant gas discharge path 137. Specifically, the oxidant gas supply switch 104A is provided in the middle of the oxidant gas connection path 135, and the oxidant gas bypass path 104B is connected at its upstream end to the oxidant gas supply switch 104A. In addition, the downstream end is connected to the middle of the oxidant gas discharge path 137.

  Even the fuel cell system 100 of the first modification configured as described above has the same effects as the fuel cell system 100 according to the first embodiment.

[Modification 2]
FIG. 7 is a schematic diagram showing a schematic configuration of a fuel cell system of Modification 2 of the fuel cell system according to Embodiment 1. In FIG. FIG. 7 shows the flow of the reaction gas and the cooling medium during the deterioration suppressing power generation operation of the fuel cell system.

  As shown in FIG. 7, the fuel cell system 100 of Modification 2 has the same basic configuration as the fuel cell system 100 according to Embodiment 1, but each flow path provided in the first cell block 51. And the respective flow paths provided in the second cell block 52 are connected in parallel.

  Specifically, the upstream end of the fuel gas connection path 134 is connected in the middle of the fuel gas supply path 132, and the fuel gas flow path 132 and the fuel gas connection path 134 allow the fuel gas flow path inside the second cell block to be connected. An inlet of 52A and an inlet of the first cell block internal fuel gas flow path 51A are connected in parallel. A fuel gas discharge path 136 is connected to the outlet of the second cell block internal fuel gas flow path 52A. As a result, part of the fuel gas supplied from the fuel gas supply device 102 to the fuel gas supply path 132 is diverted to the fuel gas connection path 134. In this way, the fuel gas is supplied to each of the first cell block internal fuel gas flow path 51A and the second cell block internal fuel gas flow path 52A. The fuel gas supplied to the first cell block internal fuel gas flow path 51A and the second cell block internal fuel gas flow path 52A is discharged from the fuel gas discharge path 136, respectively.

  The upstream end of the oxidant gas connection path 135 is connected in the middle of the oxidant gas supply path 133, and the second cell block internal oxidant gas is formed by the oxidant gas supply path 133 and the oxidant gas connection path 135. The inlet of the flow path 52B and the inlet of the first cell block internal oxidant gas flow path 51B are connected in parallel. An oxidant gas discharge path 137 is connected to the outlet of the second cell block internal oxidant gas flow path 52B. As a result, part of the oxidant gas supplied from the oxidant gas supply unit 103 to the oxidant gas supply path 133 is diverted to the oxidant gas connection path 135. In this way, the oxidant gas is supplied to each of the first cell block internal oxidant gas flow path 51B and the second cell block internal oxidant gas flow path 52B. The oxidant gas supplied to the first cell block internal oxidant gas flow path 51B and the second cell block internal oxidant gas flow path 52B is discharged from the oxidant gas discharge path 137, respectively.

  Further, the upstream end of the cooling medium connection flow path 139 is connected in the middle of the cooling medium supply path 138, and the second cell block cooling medium internal flow path is formed by the cooling medium supply path 138 and the cooling medium connection flow path 139. The inlet of 52C and the inlet of the first cell block cooling medium internal flow path 51C are connected in parallel. A cooling medium discharge path 140 is connected to the outlet of the first cell block cooling medium internal flow path 51C. Thereby, a part of the cooling medium supplied from the cooling medium supply unit 105 to the cooling medium supply path 138 is diverted to the cooling medium connection channel 139. In this way, the cooling medium is supplied to the first cell block cooling medium internal flow path 51C and the second cell block cooling medium internal flow path 52C. The cooling medium supplied to the first cell block cooling medium internal flow path 51C and the second cell block cooling medium internal flow path 52C is discharged from the cooling medium discharge path 140, respectively.

  In the fuel cell system 100 of the second modification, the oxidant gas supply blocking mechanism 104 is configured by an on-off valve and is disposed in the middle of the oxidant gas supply path 133. The oxidant gas bypass path 104B also serves as the oxidant gas connection path 135. For this reason, in the operation stop operation of the fuel cell system 100, the on-off valve, which is the oxidant gas supply shut-off mechanism 104, closes the valve body so that the oxidant into the second cell block internal oxidant gas flow path 52B. Shut off gas supply.

  Even the fuel cell system 100 according to the second modification configured as described above has the same operational effects as the fuel cell system 100 according to the first embodiment.

  In the fuel cell system 100 of the second modification, the first cell block cooling medium internal flow path 51C and the second cell block cooling medium internal flow path 52C are connected in parallel. However, the present invention is not limited to this. Similarly to the first embodiment, the first cell block cooling medium internal flow path 51C and the second cell block cooling medium internal flow path 52C may be connected in series. Moreover, although the form which connects 51 A of 1st cell block internal fuel gas flow paths and 52 A of 2nd cell block internal fuel gas flow paths in parallel was employ | adopted, it is not limited to this, Like Embodiment 1, 1st A mode in which the cell block internal fuel gas flow path 51A and the second cell block internal fuel gas flow path 52A are connected in series may be employed.

[Modification 3]
FIG. 8 is a schematic diagram showing a schematic configuration of a fuel cell system of Modification 3 of the fuel cell system according to Embodiment 1. In FIG. FIG. 8 shows the flow of the reaction gas and the cooling medium during the deterioration suppressing power generation operation of the fuel cell system.

  As shown in FIG. 8, the basic configuration of the fuel cell system 100 of Modification 3 is the same as that of the fuel cell system 100 according to Embodiment 1, but there are a plurality of first cell blocks 51 (two in this case). ) Different points are provided. Specifically, the first cell block 51 is further arranged on the downstream side of the first cell block 51 as viewed from the flow direction of the reaction gas, and these first cell blocks 51 are connected in series. .

  In the following description, the first cell block 51 disposed on the upstream side when viewed from the flow direction of the reaction gas is referred to as the upstream first cell block 51, and the first cell disposed on the downstream side. The block 51 is referred to as a downstream first cell block 51.

  More specifically, the upstream first cell block 51 and the downstream first cell block 51 are connected in series by a fuel gas connection path 134, an oxidant gas connection path 135, and a cooling medium connection flow path 139. In addition, a fuel gas discharge path 136, an oxidant gas discharge path 137, and a cooling medium discharge path 140 are connected to the downstream first cell block 51, respectively. In the third modification, the second cell block 52, the upstream first cell block 51, and the downstream first cell block 51 are connected in series. However, the present invention is not limited to this, and the second cell block 52 and the upstream The side first cell block 51 and the downstream side first cell block 51 may be connected in parallel, and either the upstream side first cell block 51 or the downstream side first cell block 51 The second cell block 52 may be connected in series, and the other first cell block 512 may be connected in parallel with the second cell block 52.

  Even the fuel cell system 100 of the third modification configured as described above has the same effects as the fuel cell system 100 according to the first embodiment.

  In addition, in the fuel cell system 100 of the third modification, a form including a plurality of first cell blocks 51, that is, a first cell block group is adopted, but is not limited thereto, and a plurality of second cell blocks 52, That is, you may employ | adopt the form provided with a 2nd cell block group. In this case, a form including the second cell block group and one first cell block 51 may be adopted, and a form including one second cell block 52 and the first cell block group as in the present modification. You may employ | adopt and the form provided with a 2nd cell block group and a 1st cell block group may be employ | adopted. The first cell block 51 and the second cell block 52 may be connected in series or may be connected in parallel. Further, when the first cell block (group) and the second cell block (group) are connected in series, the order in which the first cell block (group) and the second cell block (group) are arranged is not limited as viewed from the flow direction of the reaction gas.

(Embodiment 2)
The fuel cell system according to Embodiment 2 of the present invention exemplifies an aspect including a pressure detector that detects the pressure in the second cell block internal oxidant gas flow path.

[Configuration of fuel cell system]
FIG. 9 is a schematic diagram showing a schematic configuration of a fuel cell system according to Embodiment 2 of the present invention. FIG. 9 shows the flow of the reaction gas and the cooling medium during the deterioration suppressing power generation operation of the fuel cell system.

  As shown in FIG. 9, the basic configuration of the fuel cell system 100 according to Embodiment 2 of the present invention is the same as that of the fuel cell system 100 according to Embodiment 1, but instead of the voltage detector 106, The difference is that a pressure detector 108 for detecting the pressure in the second cell block internal oxidant gas flow path 52B of the second cell block 52 is provided. The pressure detector 108 may take any form as long as it can detect the pressure in the second cell block internal oxidant gas flow path 52 </ b> B and output the detected pressure to the controller 110.

[Operation of fuel cell system]
Next, the operation of the fuel cell system 100 according to Embodiment 2 will be described with reference to FIGS. 9 and 10. FIG. 10 is a flowchart schematically showing a stop operation of the fuel cell system 100 according to the second embodiment.

  As shown in FIG. 10, the stop operation of the fuel cell system 100 according to the second embodiment is basically the same as the stop operation of the fuel cell system 100 according to the first embodiment. The difference is that step S103A and step S104A are performed instead of S104. Specifically, the controller 110 outputs an oxidant gas supply cut-off command to the second cell block 52 to the oxidant gas supply cut-off mechanism 104 (step S102), and causes the deterioration-suppressing power generation to be performed. The pressure detected by the pressure detector 108 is acquired (step S103A).

  Next, the controller 110 determines whether or not the pressure acquired in step S103A has changed from a downward trend to an upward trend (step S104A). As described above, in the second cell block 52, the oxidant gas in the second cell block internal oxidant gas flow path 52B is consumed. When the oxidant gas remaining in the second cell block internal oxidant gas flow path 52B is sufficiently reduced (the oxidant gas in the second cell block 52 is almost completely consumed), the cathode electrode 4B. Then, a hydrogen generation reaction occurs. For this reason, the pressure in the second cell block internal oxidant gas flow path 52B of the second cell block 52 increases after decreasing.

  That is, in the second embodiment, the potential of the cathode electrode 4B of the second cell block 52 is lower than the potential of the anode electrode 4A by detecting the pressure in the second cell block internal oxidant gas flow path 52B. It is trying to detect the state that became.

  Then, when the pressure has not changed from the downward trend to the upward trend (when the pressure has not increased) (No in step S104A), the controller 110 returns to step S103A and continues to step S103A until the pressure increases. Step S104A is repeated. On the other hand, when the pressure increases (Yes in step S104A), the controller 110 proceeds to step S105 to stop the voltage detector 106 from supplying power to the external power load, and the fuel gas supplier 102 and The oxidant gas supply unit 103 is stopped (step S106).

  Even the fuel cell system 100 according to the second embodiment configured as described above has the same effects as the fuel cell system 100 according to the first embodiment.

  Next, experimental examples will be described.

[Experimental example]
First, a fuel cell (single cell) 101 was produced as follows.

  As a catalyst carrier used for the cathode catalyst layer 2B, a catalyst carrier A, a catalyst carrier B, and a catalyst carrier C in which platinum cobalt alloy particles (electrocatalysts) are supported on different types of carbon powders were prepared. In addition, the crystallinity (G-band peak half width and water content) of the catalyst carriers A to C will be described later. Then, each catalyst carrier and a polymer electrolyte solution having hydrogen ion conductivity (Flemion manufactured by Asahi Glass Co., Ltd.) are dispersed in a mixed dispersion medium (mass ratio 1: 1) of ethanol and water to form a cathode catalyst layer. A forming ink was prepared. At this time, the mass of the polymer electrolyte solution was adjusted so that the ratio (WP / WCat-C) of the mass WP of the polymer electrolyte to the mass WCat-C of the carbon powder was 0.8.

Next, using the obtained cathode catalyst layer forming ink, it was applied to one surface of the polymer electrolyte membrane 1 (GSII manufactured by Japan Gore-Tex Co., Ltd.) by a spray method, and the platinum loading amount was 0.3 mg. A cathode catalyst layer 2B having a size of 140 mm × 140 mm at / cm ² was formed.

On the other hand, as the catalyst carrier used for the anode catalyst layer 2A, a catalyst carrier (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) obtained by supporting platinum ruthenium alloy particles (electrode catalyst) on carbon powder having a specific surface area of 800 m ² / g. TEC61E54) was used. The catalyst carrier and polymer electrolyte solution (Flemion manufactured by Asahi Glass Co., Ltd.) were dispersed in a mixed dispersion medium (mass ratio 1: 1) of ethanol and water to prepare an anode catalyst layer forming ink. At this time, as in the case of the cathode catalyst layer 2B, the ratio of the mass WP of the polymer electrolyte to the mass WCat-C of the carbon powder (WP / WCat-C) is 0.8 so that the polymer electrolyte solution The mass was adjusted.

Next, the obtained anode catalyst layer forming ink is sprayed onto the surface of the polymer electrolyte membrane 1 opposite to the surface on which the cathode catalyst layer 2B is formed (the other surface of the polymer electrolyte membrane 1). The anode catalyst layer 2A having a platinum loading of 0.1 mg / cm ² and dimensions of 140 mm × 140 mm was formed to prepare a membrane-catalyst layer assembly.

  Using the membrane-catalyst layer assembly produced as described above, a membrane electrode assembly was produced as follows.

  In order to form a gas diffusion layer, a carbon cloth having a thickness of 270 μm (SK-1 manufactured by Mitsubishi Chemical Corporation) was impregnated into an aqueous dispersion containing fluororesin (ND-1 manufactured by Daikin Industries, Ltd.). Then, the carbon cloth was given water repellency by drying (water repellency treatment).

  Subsequently, a water repellent carbon layer was formed on one surface (entire surface) of the carbon cloth after the water repellent treatment. Specifically, a conductive carbon powder (Denka Black manufactured by Denki Kagaku Kogyo Co., Ltd.) and an aqueous solution (D-1 manufactured by Daikin Kogyo Co., Ltd.) in which fine powder of polytetrafluoroethylene (PTFE) is dispersed are used. By mixing, an ink for forming a water-repellent carbon layer was prepared. This water repellent carbon layer forming ink was applied to one surface of the carbon cloth after the water repellent treatment by a doctor blade method to form a water repellent carbon layer. At this time, a part of the water repellent carbon layer was embedded in the carbon cloth.

Next, the carbon cloth after the water repellent treatment and the formation of the water repellent carbon layer was baked for 30 minutes at 350 ° C., which is a temperature equal to or higher than the melting point of PTFE, to obtain a gas diffusion layer. The membrane-catalyst layer assembly is sandwiched between the two gas diffusion layers so that the central portion of the water-repellent carbon layer in the obtained gas diffusion layer is in contact with the anode catalyst layer 2A (or the cathode catalyst layer 2B). MEA5 was obtained by thermocompression bonding (120 ° C., 30 minutes, 10 kgf / cm ² ) with a hot press machine.

  The gasket 7 is arranged around the polymer electrolyte membrane 1 of the MEA 5 thus obtained, the MEA 5 and the gasket 7 are sandwiched between the anode separator 6A and the cathode separator 6B, and fastened with a fastener. Was made.

(Evaluation Test 1)
In the evaluation test 1, the power generation performance of the fuel cell 101 under low humidification conditions, the G-band peak half width and the moisture content of the catalyst carriers A to C were measured.

  Specifically, a cooling medium (here, water) is passed through the cooling medium flow path 10 so that the temperature of the fuel cell 101 becomes 90 ° C., and a mixed gas of 75% hydrogen + 25% carbon dioxide is used as the fuel gas. Was supplied to the fuel gas channel 8 and air was supplied to the oxidant gas channel 9 as an oxidant gas. At this time, the fuel gas and the dew point of the air were both humidified so as to be 65 ° C. and then supplied.

The current density was set to 0.16 mA / cm ² , the hydrogen gas utilization rate was set to 75%, the air utilization rate was set to 55%, and the output voltage of the fuel cell 101 after 12 hours was measured. Further, the G-band peak half-value widths of the catalyst carriers A to C were measured with a Raman spectrometer. Furthermore, the moisture content of the catalyst supports A to C under 80 ° C. and 90% RG saturated steam conditions was measured using a moisture adsorption / desorption measuring device. These results are shown in FIG.

  FIG. 11 shows the results of evaluation test 1 (the voltage (relative value) of the fuel cell (single cell) using the catalyst carriers A to C and the G-band peak half-value width of the catalyst carriers A to C, 80 ° C., 90 ° C. It is the table | surface which showed the water content in% RH saturated water vapor | steam. As shown in FIG. 11, it can be seen that the catalyst carrier A having a high water content has a large D-band peak half width and low crystallinity. It can also be seen that the fuel cell 101 using the catalyst carrier A has high cell performance. On the other hand, the catalyst carrier B and the catalyst carrier C having a low water content have high crystallinity, but the fuel cell 101 using these catalyst carriers has low cell performance.

(Evaluation test 2)
In the evaluation test 2, a catalyst deterioration test accompanying repeated starting (power generation) / stopping of the three types of fuel cells 101 produced as described above was performed by measuring the voltage of the fuel cell 101.

  Specifically, the cooling medium (here, water) is passed through the cooling medium internal flow path from the cooling medium supply unit 105 through the cooling medium supply path 138 so that the temperature of the fuel cell 101 becomes 65 ° C. I let you. Further, a mixed gas of 75% hydrogen + 25% carbon dioxide was supplied from the fuel gas supply device 102 to the fuel gas internal flow path via the fuel gas supply path 132 as the fuel gas. Air as oxidant gas was supplied from the oxidant gas supply device 103 to the oxidant gas internal flow path via the oxidant gas supply path 133. At this time, the fuel gas and the dew point of the air were both humidified so as to be 65 ° C. and then supplied.

Then, an open circuit state was maintained for 2 minutes with fuel gas and air being supplied (activation of the fuel cell 101). Next, power was generated at a current density of 0.16 mA / cm ² , a hydrogen gas utilization rate of 75% and an air utilization rate of 55% (power generation of the fuel cell 101), and the output voltage of the fuel cell 101 was measured. And 28 minutes after the start of power generation, the circuit was returned to the open circuit state again, and the supply of fuel gas and air was stopped. At that time, the inlets of the fuel gas internal channel and the oxidant gas internal channel were sealed by valves provided in the middle of the fuel gas supply channel 132 and the oxidant gas supply channel 133, respectively. Further, the outlets of the fuel gas internal flow path and the oxidant gas internal flow path were sealed by immersing the downstream ends of the fuel gas discharge path 136 and the oxidant gas discharge path 137 connected to the respective outlets in water. This state was continued for 30 minutes (stop of the fuel cell 101). Thereafter, the fuel cell 101 was started again, and a series of operations such as power generation and stop were repeated. The result is shown in FIG.

  FIG. 12 is a graph showing the results of evaluation test 2. As shown in FIG. 12, in the fuel cell 101 using the catalyst carrier B and the catalyst carrier C, the voltage obtained by comparing the voltage before the start / stop repetition test and the voltage after 4000 start / stop repetitions. The deterioration rate was 5% or less. On the other hand, in the fuel cell 101 using the catalyst carrier A, the voltage deterioration rate comparing the voltage before the start / stop repetition test and the voltage after 1600 start / stop repetitions decreased by 8% or more. Accordingly, the fuel cell 101 using the catalyst carrier B and the catalyst carrier C has durability that can withstand practical use even if a normal stop process is performed. However, the fuel cell 101 using the catalyst carrier A has a special durability. It was suggested that sufficient durability could not be ensured without proper stopping treatment.

  From these evaluation tests, it was found that the fuel cell 101 of the catalyst carrier A using the carbon powder having low crystallinity can sufficiently exhibit the cell performance, but is easily deteriorated by the normal stop treatment. . Further, it has been found that the fuel cell 101 of the catalyst carrier B and the catalyst carrier C using carbon powder having high crystallinity has low battery performance but has sufficient durability even in a normal stop treatment.

  Thus, the present inventors have found that the use of carbon powders having different crystallinity in different cells (cell stacks) can achieve both improvement in battery performance and improvement in durability, and have conceived the present invention. . That is, when the fuel cell system is stopped, by using the first cell (first cell stack (group)) using carbon powder having high crystallinity, the durability is maintained even if normal stop processing is performed. In addition, by using the second cell (second cell stack (group)) using carbon powder having low crystallinity, the battery performance is improved, and when the fuel cell system is stopped, the oxidant to the second cell It has been found that by stopping the supply of gas, the oxidant gas in the second cell is sufficiently reduced and catalyst deterioration is suppressed, thereby improving durability.

  From the foregoing description, many modifications and other embodiments of the present invention are obvious to one skilled in the art. Accordingly, the foregoing description should be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The details of the structure and / or function may be substantially changed without departing from the scope of the invention. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment.

  In the fuel cell system and the operation method of the fuel cell system of the present invention, high durability can be realized by suppressing carbon deterioration of the catalyst layer when the fuel cell system is stopped. Useful in the field.

DESCRIPTION OF SYMBOLS 1 Polymer electrolyte membrane 2A Anode catalyst layer 2B Cathode catalyst layer 3A Anode gas diffusion layer 3B Cathode gas diffusion layer 4A Anode electrode 4B Cathode electrode 5 MEA (Membrane-Electrode-Assembly: membrane-electrode assembly)
6A Anode separator 6B Cathode separator 7 Gasket 8 Fuel gas flow path 9 Oxidant gas flow path 10 Cooling medium flow path 21 First cell 22 Second cell 32 Fuel gas supply manifold 33 Oxidant gas supply manifold 34 Fuel gas discharge manifold 35 Oxidation Agent gas discharge manifold 38 Cooling medium supply manifold 39 Cooling medium discharge manifold 51 First cell block 51A First cell block internal fuel gas flow path 51B First cell block internal oxidant gas flow path 51C First cell block cooling medium internal flow path 52 2nd cell block 52A 2nd cell block internal fuel gas flow path 52B 2nd cell block internal oxidant gas flow path 52C 2nd cell block cooling medium internal flow path 61 End plate 62 End plate 70 Cell laminated body 100 Fuel cell system 101 burning Battery 102 Fuel gas supply device 103 Oxidant gas supply device 104 Oxidant gas supply shut-off mechanism 104A Oxidant gas supply switch 104B Oxidant gas bypass path 105 Cooling medium supply device 106 Voltage detector 107 Power regulator 108 Pressure detector 110 Controller 132 Fuel gas supply path 133 Oxidant gas supply path 134 Fuel gas connection path 135 Oxidant gas connection path 136 Fuel gas discharge path 137 Oxidant gas discharge path 138 Cooling medium supply path 139 Cooling medium connection path 140 Cooling medium discharge Route 161 Electrical wiring

Claims (10)

First cell block group and anode having one or more first cell blocks formed by laminating a cell having an anode, a cathode, and an anode and an electrolyte layer sandwiched between the cathode, a cathode, the anode, A fuel cell having a second cell block group having one or more second cell blocks formed by laminating cells having an electrolyte layer held between the cathodes;
A fuel gas supplier for supplying fuel gas to the first cell block group and the second cell block group of the fuel cell via a fuel gas supply path;
An oxidant gas supplier for supplying an oxidant gas to the first cell block group and the second cell block group of the fuel cell via an oxidant gas supply path;
An oxidant gas supply shut-off mechanism configured to shut off the supply of the oxidant gas to the second cell block group of the fuel cell;
A controller, and
The first cell block group and the second cell block group are electrically connected in series,
The cathode of the first cell block group includes a first cathode catalyst layer having a first catalyst support including an electrode catalyst and a first carbon powder supporting the electrode catalyst,
The cathode of the second cell block group has a second cathode catalyst layer having an electrode catalyst and a second catalyst support including a first carbon powder supporting the electrode catalyst,
The crystallinity of the second carbon powder is lower than the crystallinity of the first carbon powder,
The controller operates the fuel gas supply unit and the oxidant gas supply unit, and shuts off the supply of the oxidant gas to the second cell block group by the oxidant gas supply cutoff mechanism. Deterioration suppression power generation,
Then, the fuel cell system which stops the fuel gas supply unit and the oxidant gas supply unit. 2. The fuel cell according to claim 1, wherein the first catalyst carrier has a G-band peak half-width of 60 cm ⁻¹ or less, and the second catalyst carrier has a G-band peak half-width of 60 cm ^{−1 or} more. system.   2. The fuel cell system according to claim 1, wherein a moisture content of the second catalyst carrier is higher than a moisture content of the first catalyst carrier. Under the conditions of 80 ° C. and 90% RH saturated steam, the water content of the first catalyst carrier is 0.31 g-H ₂ O / g-C or less, and the water content of the second catalyst carrier is 0.31 g. -H larger ₂ O / g-C, the fuel cell system according to claim 3.   In the controller, the relative humidity of the oxidant gas flowing through the second cell block group of the fuel cell is lower than the relative humidity of the oxidant gas flowing through the first cell block group. The fuel cell system according to claim 1, wherein the fuel cell system is configured to control power generation of the fuel cell.   2. The fuel cell system according to claim 1, wherein the controller stops the fuel gas supply unit and the oxidant gas supply unit when a cathode potential of the second cell block group becomes lower than an anode potential. 3. A voltage detector for detecting a voltage of the second cell block group;
The fuel cell system according to claim 6, wherein the controller stops the fuel gas supply device and the oxidant gas supply device when the voltage detected by the voltage detector is inverted. The second cell block group is provided with a second cell block internal oxidant gas flow channel that passes through each cell block and flows the oxidant gas so as to divert each cell of each cell block,
The fuel cell system further includes a pressure detector that detects a pressure of the oxidant gas flow path inside the second cell block,
The fuel cell system according to claim 6, wherein the controller stops the fuel gas supply device and the oxidant gas supply device when the pressure detected by the pressure detector changes from a decreasing tendency to an increasing tendency. The first cell block is provided with a first cell block internal cooling medium flow path that passes through the first cell block and flows the cooling medium so as to divert each cell of each cell block,
The second cell block is provided with a second cell block internal cooling medium flow path that passes through the second cell block and flows the cooling medium so as to divert each cell of each cell block.
2. The fuel cell system according to claim 1, wherein the first cell block internal cooling medium flow path and the second cell block internal cooling medium flow path are connected in series by a cooling medium connection path. A method for operating a fuel cell system, comprising:
The fuel cell system includes:
A fuel cell having a first cell block group and a second cell block group in which cells having an anode, a cathode, and an electrolyte layer sandwiched between the anode and the cathode are stacked;
A fuel gas supplier for supplying fuel gas to the first cell block group and the second cell block group of the fuel cell via a fuel gas supply path;
An oxidant gas supplier for supplying an oxidant gas to the first cell block group and the second cell block group of the fuel cell via an oxidant gas supply path;
An oxidant gas supply shut-off mechanism configured to shut off the supply of the oxidant gas to the second cell block of the fuel cell,
The first cell block group and the second cell block group are electrically connected in series,
The cathode of the first cell block has a first cathode catalyst layer having a first catalyst support including an electrode catalyst and a first carbon powder supporting the electrode catalyst;
The cathode of the second cell block has a second cathode catalyst layer having a second catalyst carrier including an electrode catalyst and a first carbon powder supporting the electrode catalyst;
The crystallinity of the second carbon powder is lower than the crystallinity of the first carbon powder,
The oxidant gas supply shut-off mechanism shuts off the supply of the oxidant gas to the second cell block group and performs deterioration suppressing power generation,
Thereafter, the fuel gas supply device and the oxidant gas supply device are stopped.

Images