JP2008027700A - Catalyst recovery method from fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simply recovery a catalyst from a fuel cell without having to use special equipment. <P>SOLUTION: A method for recovering the catalyst, constituting an electrode from the fuel cell, contains a first process (step S110 and step S120) for supplying a catalyst-dissolving solution, capable of dissolving the catalyst to a gas passage formed in the fuel cell for supplying a reactant gas to the electrode, and a second process (step S130) for recovering the catalyst dissolving solution passed through the gas passage. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for recovering a catalyst from a fuel cell.

  In general, a fuel cell includes a catalyst layer containing a metal such as a noble metal on both sides of an electrolyte layer, and hydrogen is supplied to the anode side and oxygen is supplied to the cathode side to advance an electrochemical reaction. To obtain an electromotive force. Such a fuel cell is a highly efficient power generation device that directly converts chemical energy of fuel into electric energy, and is expected to spread as a power generation device that does not discharge environmental pollutants. Here, in order to spread the fuel cell, it is considered important to attempt to reuse the components of the fuel cell such as a catalyst. As a method of recovering the catalyst from the fuel cell for reuse, it is a waste material obtained by disassembling the fuel cell, and the noble metal contained in the electrode waste material from the electrode waste material including the electrode portion is used using aqua regia etc. There is known an acid extraction method in which the acid is dissolved (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 63-210246 JP 2005-209624 A JP-A-8-171922

  However, when precious metals are dissolved from electrode waste materials using aqua regia etc., special equipment such as a solution tank for immersing electrode waste materials obtained by disassembling the fuel cell in aqua regia is required. . In addition, when the operation of disassembling the fuel cell and taking out the electrode waste material or the like is manual, it may be difficult to efficiently recover the catalyst because of the limited amount of disassembly work.

  The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to easily recover a catalyst from a fuel cell without using special equipment.

To achieve the above object, the present invention provides a method for recovering a catalyst constituting an electrode from a fuel cell,
A first step of supplying a catalyst solution capable of dissolving the catalyst to a gas flow path formed in the fuel cell to supply a reaction gas to the electrode;
And a second step of recovering the catalyst solution that has passed through the gas flow path.

  According to the catalyst recovery method from the fuel cell of the present invention configured as described above, the catalyst solution in the electrode is brought into the catalyst solution by supplying the catalyst solution to the gas flow path formed in the fuel cell. It can be dissolved and recovered. Therefore, it is not necessary to prepare special equipment for immersing the members constituting the fuel cell, and the equipment for collecting the catalyst can be simplified and the catalyst can be recovered by a simple operation. Further, when recovering the catalyst in this way, an operation of disassembling the fuel cell is not necessary, and the catalyst recovery process can be further simplified.

In the method for recovering the catalyst from the fuel cell of the present invention,
The fuel cell is composed of a stack in which a plurality of single cells are stacked,
The gas flow path includes a gas flow path in a single cell that is a gas flow path formed in each single cell, and a gas that supplies and discharges the reaction gas to and from each gas flow path in the single cell. A supply and exhaust gas flow path that is a flow path,
The first step may be a step of supplying the catalyst solution to the supply / exhaust gas flow path.

  With such a configuration, in the first step, the catalyst solution may be supplied to the supply / exhaust gas flow path for supplying and discharging the reaction gas to each of the stacked single cells. The catalyst recovery from the plurality of stacked single cells can be efficiently performed using the existing gas flow path. Moreover, the effect which can simplify the installation for catalyst collection | recovery by utilizing the existing gas flow path can be acquired more notably. In addition, the catalyst can be recovered without disassembling the fuel cell, so that the effect of simplifying the catalyst recovery operation can be obtained more remarkably.

In the method for recovering the catalyst from the fuel cell of the present invention,
The first step is a step of circulating the catalyst solution after supplying a predetermined amount of the catalyst solution to the gas flow path;
The second step may be a step of collecting the catalyst solution circulated through the gas flow path.

  With such a configuration, a larger amount of catalyst can be recovered from the fuel cell using a certain amount of catalyst solution.

In the method for recovering the catalyst from the fuel cell of the present invention,
The catalyst solution may be a solution that substantially dissolves only the catalyst among the members disposed around the gas flow path in the fuel cell.

  With such a configuration, the catalyst can be dissolved and recovered in the catalyst solution with fewer components other than the catalyst.

  In the catalyst recovery method from the fuel cell of the present invention, the catalyst may contain a noble metal. By making it possible to recover rare noble metals by a simple method, it is possible to promote the spread of fuel cells using noble metals as catalysts.

In such a catalyst recovery method from the fuel cell of the present invention,
The fuel cell is further disposed between a gas separator made of carbon constituting a wall surface of the flow path of the reaction gas in a single cell constituting the fuel cell, the electrode and the gas separator, A gas flow path forming member made of carbon that forms the flow path of the reaction gas in a single cell, and a solid polymer electrolyte membrane as an electrolyte layer,
The catalyst solution may be an acid solution.

  With such a configuration, since the acid solution does not dissolve the solid polymer electrolyte membrane and carbon, the catalyst containing the noble metal can be efficiently recovered.

In the method for recovering a catalyst from the fuel cell of the present invention,
A third step of separating and purifying the catalyst from the recovered catalyst solution may be provided.

  With such a configuration, the catalyst separated from the fuel cell can be easily reused.

  The present invention can be realized in various forms other than those described above. For example, the present invention can be realized in a form such as a method of reusing components of a fuel cell.

Next, embodiments of the present invention will be described in the following order based on examples.
A. Fuel cell configuration:
B. Operation of catalyst recovery:
C. Variation:

A. Fuel cell configuration:
First, the configuration of a fuel cell to which the catalyst recovery method from the fuel cell as an embodiment is applied will be described. FIG. 1 is a schematic cross-sectional view showing an outline of a configuration of a polymer electrolyte fuel cell that is a target of catalyst recovery, and FIG. 2 is an exploded perspective view. This fuel cell has a stack structure in which a plurality of single cells are stacked. FIG. 1 and FIG. 2 show the configuration of the fuel cell with a single cell 10 as a stack unit as a center. In FIG. 2, the position of the cross section shown in FIG. 1 is shown as a 1-1 cross section.

  The single cell 10 constituting the fuel cell includes an electrolyte membrane 20, a cathode 21 and an anode 22, gas diffusion layers 23 and 24, and gas separators 25 and 26. Here, the cathode 21 and the anode 22, which are electrodes, are formed on the electrolyte membrane 20, and the electrolyte membrane 20 with the electrodes formed on the surface is sandwiched between gas diffusion layers 23 and 24. This sandwich structure is further sandwiched by gas separators 25 and 26 from both sides (however, the gas diffusion layer 23 is not shown in FIG. 2 because it is disposed on the back surface of the electrolyte membrane 20).

  The electrolyte membrane 20 is a proton conductive ion exchange membrane formed of a solid polymer material, for example, a fluorine-based resin, and exhibits good electrical conductivity in a wet state.

  The cathode 21 and the anode 22 include, for example, platinum or a platinum alloy as a catalyst, and are formed by supporting these catalysts on a conductive carrier. More specifically, the cathode 21 and the anode 22 include, for example, carbon particles supporting the catalyst and an electrolyte similar to the polymer electrolyte that constitutes the electrolyte membrane 20. In order to produce such a catalyst, for example, an electrode paste containing the catalyst-supporting carbon and the polymer electrolyte is produced, and this electrode paste is applied onto the electrolyte membrane 20 or the gas diffusion layers 23 and 24. What is necessary is just to dry and fix. The electrode may have a different configuration, such as not including the above-described polymer electrolyte.

  The gas diffusion layers 23 and 24 can be formed of a conductive member having gas permeability, such as carbon paper or carbon cloth. The gas diffusion layers 23 and 24 of the present embodiment are both flat plate members as a whole. Such a gas diffusion layer 24 serves as a flow path for a gas used for an electrochemical reaction and collects current.

  The gas separators 25 and 26 are made of a gas-impermeable conductive member, for example, dense carbon that has been made to be gas-impermeable by compressing carbon, or baked carbon. The gas separators 25 and 26 are members that are formed in the single cell 10 and form a wall surface of a gas flow path through which a reaction gas (a fuel gas containing hydrogen or an oxidizing gas containing oxygen) flows. A concavo-convex shape for forming a gas flow path in the single cell 10 is formed. In the single cell 10, an in-single cell oxidizing gas channel 27, which is a channel for oxidizing gas, is formed between the gas separator 25 having a groove 62 formed on the surface and the cathode 21 (see FIG. 1). . Further, between the gas separator 26 having the groove 63 formed on the surface and the anode 22, an in-single cell fuel gas channel 28 which is a fuel gas channel is formed (see FIG. 1). In the gas separator 26, a groove 62 for forming the in-single cell oxidizing gas flow path 27 is formed on the back surface of the surface on which the groove 63 for forming the in-single cell fuel gas flow path 28 is formed. The single cell 10 is formed on both sides.

  The fuel cell further includes a gas separator 29 in addition to the gas separators 25 and 26. In the gas separator 29, a groove 87 for forming an inter-cell refrigerant flow path is formed on the surface in contact with the gas separator 25. Thus, in the fuel cell, every time a predetermined number of cells are stacked, an inter-cell refrigerant flow path through which the refrigerant flows is formed between adjacent single cells. The inter-cell refrigerant flow path may be provided in all adjacent single cells. In the gas separator 29, a groove 63 for forming the in-single cell oxidizing gas flow path 28 is formed on the back surface of the surface on which the groove 87 for forming the refrigerant flow path is formed.

  The gas separators 25, 26, 29 are provided with a plurality of holes at positions corresponding to each other near the outer periphery thereof. When the fuel cell is assembled by laminating the gas separators 25, 26, 29 together with the electrolyte membrane 20 and the gas diffusion layers 23, 24, the holes provided at the corresponding positions of the separators overlap each other, A flow path penetrating the inside of the fuel cell is formed in the stacking direction. That is, the holes 83 to 86 form a gas manifold that is a supply / exhaust gas flow path for supplying and discharging reaction gas to / from the single cell gas flow path, and the holes 81 and 82 form a refrigerant manifold.

  Specifically, the hole 83 and the hole 84 that communicate with the groove 62 include a fuel gas supply manifold that distributes the oxidant gas to the oxidant gas flow paths 27 in each single cell, and the oxidant gas flow paths in each single cell. An oxidizing gas discharge manifold is formed in which the cathode exhaust gas discharged from 27 collects. Similarly, the hole 85 and the hole 86 communicating with the groove 63 form a fuel gas supply manifold and a fuel gas discharge manifold, respectively. Also, the hole 81 and the hole 82 communicating with the groove 87 are respectively a refrigerant supply manifold that distributes the refrigerant to the inter-cell refrigerant flow path, and a refrigerant discharge that collects the refrigerant discharged from the inter-cell refrigerant flow path. Form a manifold.

  FIG. 3 is a perspective view schematically showing the appearance of a fuel cell formed by a stack 15 formed by stacking the above-described members. When assembling a fuel cell including the above-described members, the members are stacked in the order shown in FIG. 2 and a predetermined number of unit cells 10 are stacked, and then current collecting plates 30 and 31, insulating plates 34, 35 and end plates 36 and 37 are sequentially arranged to complete the stack 15. When the single cells 10 are stacked, a sealing material (for example, fluororesin, butyl rubber, chlorosulfonated polyethylene (pipalon), ethylene propylene rubber (EPR) is provided between the gas separator and the periphery of the electrolyte membrane 20. ) Etc. are disposed, and the sealing performance in the gas flow path in the single cell is ensured.

  The current collecting plates 30 and 31 are formed of a gas impermeable conductive member such as dense carbon, the insulating plates 34 and 35 are formed of an insulating member such as rubber or resin, and the end plates 36 and 37 have rigidity. It is made of metal such as steel. The current collecting plates 30 and 31 are provided with output terminals 32 and 33, respectively, so that an electromotive force generated in the fuel cell can be output.

  Here, each of the current collector plate 30, the insulating plate 34, and the end plate 36 disposed on one end side of the stack 15 is provided with six holes. That is, a hole is provided at a position corresponding to each of the holes 81 to 86 provided in each gas separator. And in the end plate 36, the flow path connection parts 41-46 which are the structures for connecting a flow path are continuously provided in each of the said six hole parts (refer FIG. 3).

  When power generation by the fuel cell is performed, a flow path connection portion 45 provided continuously in the hole 85 and a fuel gas supply device (not shown) are connected, and hydrogen-rich fuel gas is supplied into the fuel cell. Similarly, a flow path connecting portion 43 provided continuously in the hole 83 is connected to an oxidizing gas supply device (not shown), and oxidizing gas (air) containing oxygen is supplied into the fuel cell. Here, the fuel gas supply device and the oxidizing gas supply device are devices that supply a fuel cell with a predetermined amount of humidification and / or pressurization for each gas. When power generation is performed by the fuel cell, the flow path connecting portion 46 provided continuously in the hole 86 and a fuel gas discharge device (not shown) are connected, and the flow path provided continuously in the hole 84. The connection portion 44 is connected to an oxidizing gas discharge device (not shown). In addition, the flow path connection portion 41 provided continuously with the hole 81 and a refrigerant supply device (not shown) are connected, and the flow path connection portion 42 provided continuously with the hole 82 and not shown. A refrigerant discharge device is connected.

  The stack 15 is held in a state where a predetermined pressing force is applied in the stacking direction. In FIG. 3, the illustration of the configuration for applying the pressing force to the stack 15 is omitted.

B. Operation of catalyst recovery:
When the fuel cell described above is disposed of, the catalyst is recovered from the fuel cell. FIG. 4 is an explanatory diagram showing a catalyst recovery process from the fuel cell. When recovering the catalyst from the fuel cell, first, a stack 15 to be recovered is prepared (step S100). The stack 15 prepared in step S100 is obtained by removing the above-described oxidizing gas supply device, oxidizing gas discharge device, fuel gas supply device, fuel gas discharge device, refrigerant supply device, and refrigerant discharge device. A predetermined pressing force is applied in the stacking direction, and the sealing performance in the internal flow path is maintained.

  After preparing the stack 15, the catalyst solution supply part 50 and the gas flow path of the fuel cell are connected (step S110). Then, the catalyst solution is circulated in the gas flow path (step S120).

  Here, the catalyst solution is capable of dissolving the catalyst included in the electrode and substantially dissolves at least a material that forms other components other than the catalyst arranged around the gas flow path in the fuel cell. Not a solution. That is, a metal such as a noble metal constituting the catalyst is dissolved, but the solid polymer electrolyte constituting the electrolyte membrane 20 and the carbon constituting the gas diffusion layers 23 and 24 or the gas separators 25 and 26 are not dissolved. As such a catalyst solution, for example, an acid solution such as aqua regia or mixed acid can be used. The composition of the catalyst solution to be used may be appropriately selected depending on the type of metal constituting the catalyst to be dissolved, but when the electrode catalyst contains platinum as in this embodiment, aqua regia is used. Is desirable. The catalyst solution supply unit 50 of this embodiment is a device that can supply a predetermined amount of the catalyst solution as described above to the fuel cell and circulate the supplied catalyst solution in the fuel cell. . Such a catalyst solution supply unit 50 may include, for example, a predetermined pressurizing unit, and the pressurizing unit may circulate the catalyst solution and allow the catalyst solution to be supplied under pressure. As the pressurizing means, for example, a pump coated with a resin such as polytetrafluoroethylene can be used.

  FIG. 5 is an explanatory view schematically showing a state in which the catalyst solution supply section 50 and the oxidizing gas flow path in the stack 15 are connected. The catalyst solution supply unit 50 includes a catalyst solution storage tank 56, a catalyst solution discharge pipe 52, and a catalyst solution recovery pipe 54. When connecting the catalyst solution supply part 50 and the gas supply path of the fuel cell in step S110, the flow path connection part 43 provided on the end plate 36 of the stack 15 and the discharge pipe 52 are connected, The flow path connecting portion 44 provided on the end plate 36 and the recovery pipe 54 are connected.

  Similarly, in step S110, the catalyst solution supply part 50 is also connected to the fuel gas flow path in the stack 15. That is, the other discharge piping (not shown) provided in the catalyst solution supply unit 50 and the flow path connection unit 45 provided in the end plate 36 are connected, and the other recovery (not shown) provided in the catalyst solution supply unit 50 is connected. The piping for use and the flow path connecting portion 46 provided on the end plate 36 are connected.

  In the stack S110, a predetermined amount of the catalyst solution is supplied from the catalyst solution storage tank 56 to the stack 15 via the discharge pipe, and the flow path in the catalyst solution supply unit 50 and the stack 15 are supplied. This catalyst solution is circulated between the gas flow paths. At this time, in the stack 15, the catalyst solution flows to the oxidizing gas discharge manifold via the oxidizing gas supply manifold and the single cell oxidizing gas flow path 27. Similarly, the catalyst solution flows to the fuel gas discharge manifold via the fuel gas supply manifold and the fuel gas flow path 28 in the single cell.

  In this way, by flowing the catalyst solution in the gas flow path in the stack 15, the catalyst is gradually dissolved into the catalyst solution. That is, the catalyst supported on the carbon particles constituting the cathode 21 is dissolved in the catalyst solution flowing in the single-cell oxidizing gas flow path 27, and the catalyst supported on the carbon particles constituting the anode 22 is simply Dissolved in the catalyst solution flowing through the in-cell fuel gas channel 28. Thus, when flowing the catalyst solution through the gas flow path in the single cell, it is easy to spread the catalyst solution to the inside of the electrode constituted by the catalyst-supported carbon particles by pressurizing the catalyst solution. Thus, the efficiency of dissolving the catalyst can be improved.

  After the catalyst solution is circulated in the gas flow path of the fuel cell, for example, for a predetermined time, the circulated catalyst solution is recovered (step S130). Specifically, the circulating catalyst solution may be discharged from the circulation channel at a predetermined location in the channel through which the catalyst solution circulates. FIG. 6 is an explanatory view schematically showing a state in which the catalyst solution circulated in the stack 15 is recovered. The connection between the recovery pipe 54 and the catalyst solution supply unit 50 is removed, and the recovery pipe is removed. A state in which the catalyst solution is recovered from 54 is shown. Thereby, recovery of the catalyst from the fuel cell can be completed in a state where the catalyst is dissolved in the catalyst solution.

  According to the method of recovering the catalyst from the fuel cell of the present embodiment configured as described above, the catalyst solution is circulated through the gas flow path formed in the fuel cell, that is, the existing flow path in the fuel cell. Because the catalyst in the electrode is dissolved and recovered in the catalyst solution, it is not necessary to prepare special equipment for immersing the members that constitute the fuel cell, and the equipment for recovering the catalyst is simplified. In addition, the catalyst can be recovered by a simple operation. Further, when recovering the catalyst in this way, an operation of disassembling the fuel cell is unnecessary, and the process of recovering the catalyst can be simplified.

  When a fuel cell is configured by a stack in which a plurality of single cells are stacked as in this embodiment, a flow path for supplying / discharging reaction gas to / from each single cell (communication with a gas flow path in a single cell) By supplying the catalyst solution to the gas manifold, the catalyst can be easily recovered from each of the stacked single cells. Therefore, the effect of simplifying the equipment for catalyst recovery and the operation of catalyst recovery can be obtained particularly remarkably. However, a fuel cell composed of a single cell may be used, and similar to this embodiment, a similar effect can be obtained by supplying a catalyst solution to an existing gas flow path and recovering the catalyst. it can.

  Further, according to this example, since the polymer electrolyte membrane is not substantially dissolved in the catalyst solution, it is not necessary to perform firing (thermal decomposition step) in order to separate the catalyst and the polymer electrolyte. . Calcination is a process in which other materials other than the catalyst can be removed from the catalyst by thermally decomposing the mixture of the catalyst and other materials, and widely used for separating the catalyst. This is the method that is performed. However, in the case where a fluorine resin such as the electrolyte membrane 20 of this embodiment is mixed with the catalyst, harmful gas is generated along with the thermal decomposition of the fluorine resin when firing is performed, and the treatment of this gas is not possible. Necessary. In this embodiment, since the catalyst and the polymer electrolyte are separated by dissolving the catalyst in the catalyst solution, there is no problem of gas treatment that occurs during firing.

  Further, according to the present embodiment, since the catalyst is not calcined to separate the catalyst and the solid polymer electrolyte, the electrolyte membrane 20 remains in the stack 15 even after the catalyst is recovered from the fuel cell. The electrolyte membrane 20 can be reused separately.

  Further, in this embodiment, when the catalyst is recovered from the fuel cell, the catalyst solution is circulated in the gas flow path in the stack 15, so that a larger amount of catalyst can be obtained using a certain amount of the catalyst solution. It can be taken out. Here, for example, when platinum is used as a catalyst and aqua regia is used as a catalyst solution, platinum is dissolved in aqua regia, thereby producing orange chloroplatinic acid. The amount of catalyst dissolved in the catalyst solution, that is, the amount of catalyst dissolved in the catalyst solution by measuring the absorbance of the catalyst solution circulated in the stack 15 using the color change when the catalyst is dissolved in the catalyst solution. The recovered amount may be calculated. In this way, when the catalyst solution is circulated in the stack 15 and the catalyst is recovered, in order to recover more catalyst, the catalyst solution is supplied and circulated in the stack 15 as described above, and thereafter The operation of collecting the catalyst solution in which the catalyst is dissolved may be repeated a plurality of times.

  Note that when the catalyst is recovered from the fuel cell by dissolving in the catalyst solution, the catalyst solution may not be circulated. In other words, the catalyst solution may be supplied to the gas flow path in the stack 15, and the catalyst solution discharged from the stack 15 after dissolving the catalyst may be recovered as it is. When the catalyst solution is not circulated, for example, the flow channel connection portions 44 and 46 that are the outlet portions of the gas flow channel may be closed prior to the supply of the catalyst solution to the stack 15. In this case, the catalyst solution is supplied into the stack 15 after the flow path connecting portions 44 and 46 are closed, and after a predetermined time has passed with the catalyst solution held in the gas flow path in the stack 15, What is necessary is just to collect | recover the catalyst solution which melt | dissolved the catalyst. Alternatively, the supply of the catalyst solution to the gas flow path in the stack 15 is started to release the internal air from the gas flow path, and then the flow path connecting portions 44 and 46 are closed, and then the gas flow The catalyst may be dissolved in a catalyst solution that stays in the channel.

  Even if the catalyst solution does not dissolve carbon other than metal or solid polymer electrolyte, for example, when the catalyst dissolves and disappears, the binding force of the carbon particles on the electrode weakens and the carbon particles peel off. It may fall and mix in the catalyst solution. Thus, even when other materials are mixed into the catalyst solution, the other materials can be easily removed from the recovered catalyst solution by, for example, filtration or centrifugation.

  After the catalyst is recovered in a state of being dissolved in the catalyst solution, the catalyst solution in which the catalyst is dissolved may be concentrated by, for example, vacuum distillation in which distillation is performed under low temperature and low pressure conditions. Then, the catalyst solution in which the catalyst is dissolved may be recovered as an insoluble salt and used for a known noble metal separation / purification step.

C. Variation:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

C1. Modification 1:
When flowing the catalyst solution in the gas flow path in the stack 15 and dissolving the catalyst in the catalyst solution, hot water may be flowed in the refrigerant flow path in the stack 15. Specifically, a hot water circulation device may be connected to the flow path connection portions 41 and 42, and hot water may flow between the refrigerant supply manifold, the inter-cell refrigerant flow path, and the refrigerant discharge manifold in the fuel cell. Thereby, the internal temperature of the stack 15 can be raised. Thus, by raising the temperature, dissolution of the catalyst in the catalyst solution can be promoted. In order to raise the temperature of the catalyst solution, the catalyst solution may be heated in advance prior to the supply of the catalyst solution to the stack 15, but instead of heating the catalyst solution or heating the catalyst solution. In addition, it is possible to easily promote the dissolution of the catalyst in the catalyst solution by flowing warm water through the refrigerant flow path.

C2. Modification 2:
The fuel cell that is the target of catalyst recovery may have a shape different from that of the embodiment. For example, instead of making the shape of the gas separator into a shape in which irregularities for forming a space to be a gas flow path in the single cell are formed on the surface, the surface forming the wall surface of the gas flow path in the single cell is a flat surface It is good also as a shape which is. In this case, instead of the gas diffusion layers 23 and 24, or in addition to the gas diffusion layers 23 and 24, between the electrode of the fuel cell and the gas separator, a flow path forming portion which is a carbon porous body And the gas flow path in the single cell may be formed by the pores formed in the flow path forming portion. In this way, the members other than the electrolyte membrane and the catalyst disposed around the reaction gas flow path in the fuel cell are formed of a material that is not substantially dissolved by the catalyst solution, such as carbon, and the catalyst solution is, for example, a king. If an acid solution such as water is used, the same effect as in the example can be obtained.

C3. Modification 3:
In the embodiment, the catalyst is recovered from the fuel cell including the electrolyte membrane 20 made of a fluorine-based solid polymer electrolyte membrane. However, the present invention may be applied to recovering the catalyst from different types of fuel cells. For example, a catalyst recovery method from a fuel cell including a hydrocarbon-based solid polymer electrolyte membrane can be used. Alternatively, the present invention can be applied even to a phosphoric acid fuel cell. It is only necessary that a catalyst solution that does not substantially dissolve other components other than the catalyst disposed around the gas flow channel is caused to flow in the gas flow channel so that the metal catalyst can be dissolved in the catalyst solution. As a result, the catalyst can be easily separated and recovered from the fuel cell without disassembling the fuel cell, and the recovery is particularly significant when the catalyst contains a noble metal.

It is a cross-sectional schematic diagram showing the outline | summary of a structure of the fuel cell used as the object of catalyst recovery. It is a disassembled perspective view showing schematic structure of a fuel cell. It is a perspective view showing the outline of the appearance of a fuel cell. It is explanatory drawing showing the catalyst collection process from a fuel cell. It is explanatory drawing showing the mode of a connection of a catalyst solution supply part and an oxidizing gas flow path. It is explanatory drawing which represents typically a mode that a catalyst solution is collect | recovered from a stack.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Single cell 15 ... Stack 20 ... Electrolyte membrane 21 ... Cathode 22 ... Anode 23, 24 ... Gas diffusion layer 25, 26, 29 ... Gas separator 27 ... Oxidation gas flow path in single cell 28 ... Oxidation gas flow path in single cell 28 ... Fuel gas flow path in a single cell 30, 31 ... Current collector plate 32, 33 ... Output terminal 34, 35 ... Insulating plate 36, 37 ... End plate 41-46 ... Flow path connection part 50 ... Catalyst solution supply part 52 ... Discharge piping 54 ... Recovery piping 56 ... Catalyst solution storage tank 62, 63 ... Groove 81-86 ... Hole 87 ... Groove

Claims (7)

A method of recovering a catalyst constituting an electrode from a fuel cell,
A first step of supplying a catalyst solution capable of dissolving the catalyst to a gas flow path formed in the fuel cell to supply a reaction gas to the electrode;
A catalyst recovery method comprising: a second step of recovering the catalyst solution that has passed through the gas flow path. The catalyst recovery method according to claim 1,
The fuel cell is composed of a stack in which a plurality of single cells are stacked,
The gas flow path includes a gas flow path in a single cell that is a gas flow path formed in each single cell, and a gas that supplies and discharges the reaction gas to and from each gas flow path in the single cell. A supply and exhaust gas flow path that is a flow path,
The first step is a step of supplying the catalyst solution to the supply / exhaust gas flow path. The catalyst recovery method according to claim 1 or 2,
The first step is a step of circulating the catalyst solution after supplying a predetermined amount of the catalyst solution to the gas flow path;
The second step is a step of recovering the catalyst solution circulated through the gas flow path. A catalyst recovery method according to any one of claims 1 to 3,
The catalyst solution is a solution that substantially dissolves only the catalyst among members arranged around the gas flow path in the fuel cell. A catalyst recovery method according to any one of claims 1 to 4,
The catalyst contains a noble metal. The catalyst recovery method according to claim 5, wherein
The fuel cell is further disposed between a gas separator made of carbon constituting a wall surface of the flow path of the reaction gas in a single cell constituting the fuel cell, the electrode and the gas separator, A gas flow path forming member made of carbon that forms the flow path of the reaction gas in a single cell, and a solid polymer electrolyte membrane as an electrolyte layer,
The catalyst solution is an acid solution. The catalyst recovery method according to any one of claims 1 to 6, further comprising:
A catalyst recovery method comprising a third step of separating and purifying the catalyst from the recovered catalyst solution.

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