JP5449758B2 - CO reduction device and fuel cell system using the same - Google Patents

Description

  The present invention relates to a CO reduction device and a fuel cell system using the same.

  A fuel cell system supplies fuel such as hydrogen and an oxidant such as air to the fuel cell and causes them to react electrochemically, thereby directly converting the chemical energy of the fuel into electrical energy and taking it out. It is. This fuel cell system is highly efficient and environmentally friendly despite its relatively small size. Moreover, it can be applied as a cogeneration system by collecting the heat generated by power generation as hot water or steam. For this reason, it is expected to be used in a wide range of applications such as business use in factories and hospitals, general household use, and automobile use.

  Examples of the fuel cell used in such a fuel cell system include a polymer electrolyte fuel cell. In a polymer electrolyte fuel cell, a membrane electrode assembly in which a fuel electrode and an oxidant electrode are bonded to both sides of a polymer electrolyte membrane is sandwiched between separators each having a fuel gas channel and an oxidant gas channel formed on both sides. It has a structure. The catalyst layer constituting part of the fuel electrode and the oxidant electrode is formed of a composite of a carbon support carrying a metal catalyst such as platinum or a platinum alloy and a polymer electrolyte. In general, a fuel cell has a stack formed by laminating a large number of single cells having such a structure.

The hydrogen supplied to the fuel electrode is supplied by reforming, for example, a hydrocarbon gas such as city gas into a fuel gas containing hydrogen as a main component in a reformer in advance. In this case, the fuel gas supplied to the fuel electrode may contain CO. When the concentration of CO in the supplied fuel gas is high, the platinum catalyst in the fuel electrode is poisoned, and the characteristics of the fuel cell system may be greatly deteriorated. As a means for preventing such CO poisoning and deterioration of the characteristics of the fuel cell system, a small amount of air is additionally supplied to the fuel electrode to oxidize and remove the CO poisoned by the catalyst in the fuel electrode, and the CO coverage on the catalyst. There is a method of preventing deterioration of the characteristics of the fuel cell system by eliminating poison (for example, see Patent Document 1).
JP 2004-241239 A

  In the method of additionally supplying a small amount of air to the fuel electrode and oxidizing and removing CO poisoned by the catalyst in the fuel electrode, oxygen molecules are present in the fuel electrode. It is known that the electrode potential of the fuel electrode is close to the hydrogen electrode potential, and when oxygen molecules are reduced to water at this electrode potential, the amount of hydrogen peroxide produced as a by-product increases rapidly.

  Hydrogen peroxide and hydroxy radicals, which are decomposition products thereof, significantly accelerate the deterioration of the polymer electrolyte membrane of the fuel cell. Further, when the concentration of CO contained in the fuel gas is high, it is necessary to increase the flow rate of additional air supplied to the fuel electrode. As the air flow rate increases, the amount of hydrogen peroxide produced in the fuel electrode also increases, so the deterioration of the polymer electrolyte membrane is further accelerated.

  Therefore, an object of the present invention is to reduce the CO concentration and the amount of hydrogen peroxide generated in the fuel electrode.

In order to achieve the above object, the present invention provides a fuel cell system comprising a fuel cell having a fuel electrode and an oxidant electrode, a fuel gas supply source for supplying fuel gas to the fuel electrode, and the fuel gas supply. A first electrode containing a catalyst formed with a first gas flow path connected to a source; a second electrode containing a catalyst formed with a second gas flow path connected to the fuel electrode; A polymer electrolyte membrane sandwiched between one electrode and the second electrode; an intermediate channel forming body that forms a channel connecting the first gas channel and the second gas channel; and the first electrode And a power source for applying a voltage between the second electrode, a CO reduction device, a thermometer for measuring the temperature of the CO reduction device, and the power supply applied based on the temperature of the CO reduction device And a control device for controlling a voltage to be generated.

According to the present invention, in the CO reduction device, a first gas flow path to which fuel gas is supplied is formed, and the first electrode containing the catalyst and the second gas flow path connected to the fuel electrode of the fuel cell are provided. A second electrode formed and containing a catalyst, a polymer electrolyte membrane sandwiched between the first electrode and the second electrode, and a flow path connecting the first gas flow path and the second gas flow path An intermediate flow path forming body that forms a gas source, and a power source that applies a voltage between the first electrode and the second electrode, and reduces CO in the fuel gas supplied to the fuel electrode A CO reduction device main body and a thermometer for measuring the temperature of the CO reduction device main body are provided, and the voltage applied from the power source is controlled based on the temperature of the CO reduction device main body. And

Further, the present invention provides a CO reduction apparatus, wherein a first gas flow path to which fuel gas is supplied is formed and a catalyst is contained, and an upstream side is connected to a downstream side of the first gas flow path and is downstream. A second gas passage having a side connected to the fuel electrode of the fuel cell and containing a catalyst; a polymer electrolyte membrane sandwiched between the first electrode and the second electrode; and the first electrode A power source for applying a voltage between the electrode and the second electrode, and a CO reduction device body that reduces CO in the fuel gas supplied to the fuel electrode, and a temperature of the CO reduction device body And a thermometer for measuring the voltage, and the voltage applied from the power source is controlled based on the temperature of the CO reduction device main body.

  According to the present invention, the CO concentration and the amount of hydrogen peroxide generated in the fuel electrode can be reduced.

  Embodiments of a fuel cell system according to the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or similar structure, and the overlapping description is abbreviate | omitted.

[First Embodiment]
FIG. 2 is a block diagram of the fuel cell system according to the first embodiment of the present invention. FIG. 3 is a cross-sectional view of the unit cell in the present embodiment.

  The fuel cell system 71 includes a fuel cell 12, a fuel gas supply source 21, an oxidant gas supply source 31, a CO reduction device 40, and a control device 50. The fuel cell 12 includes a fuel electrode 82 and an oxidant electrode 92. For example, a plurality of unit cells 10 are stacked.

  A fuel gas supply pipe 22 connects the fuel gas supply source 21 and the fuel electrode 82 of the fuel cell 12. The oxidant gas supply source 31 and the oxidant electrode 92 of the fuel cell 12 are connected by an oxidant gas supply pipe 32. A fuel gas discharge pipe 23 is connected to the fuel electrode 82 of the fuel cell 12. An oxidant gas discharge pipe 33 is connected to the oxidant electrode 92 of the fuel cell 12.

  The fuel gas supply source 21 is a reformer that reforms a hydrocarbon-based gas such as city gas into a fuel gas containing hydrogen. The oxidant gas supply source 31 is, for example, a blower or a pump that supplies air in the atmosphere. An oxygen cylinder or an air cylinder can also be used as the oxidant gas supply source 31.

  The CO reduction device 40 is provided in the middle of the fuel gas supply pipe 22. The control device 50 is provided so that the CO reduction device 40 can be controlled.

  The unit cell 10 is formed by sandwiching the polymer electrolyte membrane 16 between the fuel electrode 82 and the oxidant electrode 92. The fuel electrode 82 is obtained by sequentially stacking a fuel electrode gas diffusion layer 84 and a fuel electrode gas flow path plate 85 on a fuel electrode catalyst layer 83 facing the polymer electrolyte membrane 16. A fuel gas passage 88 is formed in the fuel electrode gas passage plate 85 so as to face the fuel electrode gas diffusion layer 84. The fuel electrode gas diffusion layer 84 is formed of carbon paper, carbon cloth, or a carbon powder bound thereto. The fuel electrode catalyst layer 83 is formed of a carbon support, metal particles, and an electrolyte. The metal particles are, for example, an alloy of platinum and ruthenium, and are supported on the carbon support and held in the fuel electrode catalyst layer 83.

  The oxidant electrode 92 is formed by sequentially laminating an oxidant electrode gas diffusion layer 94 and an oxidant electrode gas channel plate 95 on an oxidant electrode catalyst layer 93 facing the polymer electrolyte membrane 16. The oxidant electrode gas flow path plate 95 forms an oxidant gas flow path 98 so as to face the oxidant electrode gas diffusion layer 94. The oxidant electrode gas diffusion layer 94 is formed of carbon paper, carbon cloth, or a carbon powder bound thereto. The oxidant electrode catalyst layer 93 is formed of a carbon support, metal fine particles supported on the carbon support, and an electrolyte. The metal fine particles are, for example, platinum or an alloy of platinum and cobalt.

  The polymer electrolyte membrane 16 is formed such that the outer peripheral portion protrudes from the fuel electrode catalyst layer 83 and the fuel electrode gas diffusion layer 84, and the oxidant electrode catalyst layer 93 and the oxidant electrode gas diffusion layer 94. A fuel electrode gasket 87 and an oxidant electrode gasket 97 are provided between the protruding polymer electrolyte membrane 16 and the fuel electrode gas flow channel plate 85 and the oxidant electrode gas flow channel plate 95, respectively. The fuel electrode gas flow path plate 85 may be formed integrally with the oxidant electrode gas flow path plate 95 of the adjacent unit cell 10.

  FIG. 1 is a block diagram of a CO reduction device in the present embodiment.

The CO reduction device 40 constitutes the CO reduction device main body of the present embodiment , and includes a first electrode 41, a second electrode 51, a polymer electrolyte membrane 17, an intermediate pipe 64, and a power supply 18. . The polymer electrolyte membrane 17 of the CO reduction device 40 is sandwiched between the first electrode 41 and the second electrode 51. A control device 50 is connected to the power source 18. A thermometer 19 that measures the temperature of the CO reduction device 40 is connected to the control device 50.

  The first electrode 41 is formed with a first gas flow path connected to the fuel gas supply source 21 and contains a catalyst. More specifically, the first electrode 41 includes a first catalyst layer 42 and a first gas diffusion layer 43. The first electrode 41 includes a first gas flow path plate 44 in which a first gas flow path is formed. The first catalyst layer 42 is joined to the polymer electrolyte membrane 17. The first gas diffusion layer 43 is joined to the first catalyst layer 42. The first gas flow path plate 44 is joined to the first gas diffusion layer 43.

  A first gas pipe 45 is connected to the upstream side of the first gas flow path formed by the first gas flow path plate 44. The first gas pipe 45 is connected to the fuel gas supply source 21 via the fuel gas supply pipe 22.

  The second electrode 51 is formed with a second gas passage whose downstream side is connected to the fuel electrode 82 and contains a catalyst. More specifically, the second electrode 51 has a second catalyst layer 52 and a second gas diffusion layer 53. The second electrode 51 includes a second gas flow path plate 54 in which a second gas flow path is formed. The second catalyst layer 52 is bonded to the polymer electrolyte membrane 17. The second gas diffusion layer 53 is joined to the second catalyst layer 52. The second gas flow path plate 54 is joined to the second gas diffusion layer 53.

  A second gas pipe 55 is connected to the downstream side of the second gas flow path formed by the second gas flow path plate 54. The second gas pipe 55 is connected to the fuel electrode 82 of the fuel cell 12 through the fuel gas supply pipe 22.

  The first catalyst layer 42 and the second catalyst layer 52 are formed of a carbon support on which metal fine particles are supported and a polymer electrolyte. The metal particles are ruthenium or an alloy of platinum and ruthenium, and are supported on a carbon carrier and fixed to the polymer electrolyte membrane 17.

  The first gas diffusion layer 43 and the second gas diffusion layer 53 are formed of carbon paper, carbon cloth, or those obtained by binding carbon powder thereto. The first gas flow path plate 44 and the second gas flow path plate 54 are formed of a material having electronic conductivity such as carbon or metal.

  The intermediate pipe 64 connects the downstream side of the first gas flow path formed in the first gas flow path plate 44 and the upstream side of the second gas flow path formed in the second gas flow path plate 54. Forming a road. The power source 18 applies a voltage between the first electrode 41 and the second electrode 51. The voltage applied between the first electrode 41 and the second electrode 51 by the power supply 18 is controlled by the control device 50. The control device 50 controls the voltage applied by the power source 18 based on the temperature of the CO reduction device 40 measured by the thermometer 19.

  By using such a fuel cell system 71, high purity hydrogen is supplied as a fuel gas to the fuel electrode 82 of the fuel cell 12, and an oxidant gas such as air is supplied to the oxidant electrode 92. Generate electricity. The fuel cell 12 that generates electricity in this way is used by taking out the current to the outside.

  The fuel gas supplied from the fuel gas supply source 21 is sent to the CO reduction device 40 through the fuel gas supply pipe 22. The CO reduction device 40 reduces the concentration of carbon monoxide (CO) contained in the supplied fuel gas. The fuel gas with the reduced CO concentration is supplied to the fuel gas flow path 88 of the fuel cell 12. The fuel gas discharged from the fuel gas flow path 88 is discharged through the fuel gas discharge pipe 23.

  The oxidant gas supplied from the oxidant gas supply source 31 is supplied to the oxidant electrode 92 of the fuel cell 12 through the oxidant gas supply pipe 32. The oxidant gas discharged from the oxidant electrode 92 is discharged through the oxidant gas discharge pipe 33.

  Next, operation | movement of the CO reduction apparatus 40 of this Embodiment is demonstrated.

  The fuel gas sent from the fuel gas supply pipe 22 flows through the first gas pipe 45 in the direction of the dotted arrow 46 and is supplied to the first gas flow path plate 44. The fuel gas supplied to the first gas flow path plate 44 flows in the first gas flow path formed by the first gas flow path plate 44. The fuel gas discharged from the first gas flow path plate 44 flows through the intermediate pipe 64 in the direction of the dotted arrow 65 and is supplied to the second gas flow path plate 54.

  The fuel gas supplied to the second gas flow path plate 54 flows in the second gas flow path formed by the second gas flow path plate 54. The fuel gas discharged from the second gas flow path plate 54 is supplied to the fuel electrode 82 of the fuel cell 12 through the second gas pipe 55.

  The fuel gas in the first gas flow path formed by the first gas flow path plate 44 diffuses in the first gas diffusion layer 43 and reaches the first catalyst layer 42. At this time, CO contained in the fuel gas is adsorbed on the platinum-ruthenium alloy catalyst in the first catalyst layer 42.

  When the potential of the first catalyst layer 42 is greater than or equal to a predetermined potential difference (CO oxidation start potential) with respect to the potential of the second catalyst layer 52, the CO adsorbed to the platinum-ruthenium alloy catalyst in the first catalyst layer 42 is It is oxidized electrochemically according to the following formula:

CO + H ₂ O → CO ₂ + 2H ⁺ + 2e ⁻ (Formula 1)
At this time, some hydrogen in the fuel gas is electrochemically oxidized according to the following formula.

H ₂ → 2H ⁺ + 2e ⁻ (Formula 2)
In this way, protons (H ⁺ ) generated in the first catalyst layer 42 move to the second catalyst layer 52 through the polymer electrolyte membrane 17 of the CO reduction device 40. The proton that has moved to the second catalyst layer 52 is reduced to hydrogen by the platinum-ruthenium alloy catalyst in the second catalyst layer 52 according to the following formula.

2H ⁺ + 2e ⁻ → H ₂ (Formula 3)
The hydrogen reduced in the second catalyst layer 52 diffuses through the second gas diffusion layer 53 and reaches the second flow path formed by the second gas flow path plate 54. The fuel gas sent from the first electrode 41 through the intermediate pipe 64 to the second electrode 51 merges with hydrogen generated by this proton reduction reaction, and flows through the second gas pipe 55 in the direction of the dotted arrow 56. It is supplied to the fuel electrode 82 of the fuel cell 12.

  FIG. 4 is a graph showing an electrode potential scan when CO is supplied to an electrode using a platinum-ruthenium alloy catalyst at 50.degree. FIG. 4 also shows electrode potential scanning when CO is not supplied to the electrodes for comparison. The horizontal axis in FIG. 4 represents the potential (V) between the electrodes, and the vertical axis represents the current value (mA).

When CO was supplied to the electrode, when the electrode potential was scanned, a current due to CO oxidation according to Equation 1 was detected at a potential exceeding 0.3 V. On the other hand, when CO was not supplied to the electrode, no significant change was observed in the current value even when the electrode potential was scanned. This result shows that in an electrode using a platinum-ruthenium alloy catalyst, CO is oxidized to CO ₂ at 50 V or higher at 0.3 V or higher. That is, in an electrode using a platinum-ruthenium alloy catalyst, the CO oxidation start potential is about 0.3 V at 50 ° C.

  FIG. 5 is a graph showing a change in temperature of the CO oxidation start potential at an electrode using a platinum-ruthenium catalyst. The temperature of the electrode was changed in the range of 50 ° C to 80 ° C.

FIG. 5 shows that the CO oxidation start electrode potential and the electrode temperature are in a linear relationship, and the CO oxidation start potential increases as the electrode temperature decreases. Therefore, it can be said that CO is oxidized to CO ₂ by setting the potential difference between the electrodes to a portion indicated by hatching in FIG. 5 according to the temperature of the electrodes.

  Therefore, the control device 50 according to the present embodiment controls the power source 18 according to the temperature of the first catalyst layer 42 measured by the thermometer 19 so that the potential difference between the first catalyst layer 42 and the second catalyst layer 52 is increased. The potential difference is indicated by the hatched portion in FIG. For example, when the temperature of the first catalyst layer 42 is 50 ° C., the potential of the first catalyst layer 42 is set to 0.3 V or more with respect to the potential of the second catalyst layer 52. As a result, CO adsorbed on the platinum-ruthenium alloy catalyst in the first catalyst layer 42 is electrochemically oxidized according to Equation 1. As a result, the CO concentration in the fuel gas supplied from the CO reduction device 40 to the fuel electrode 82 is reduced.

  Here, the control device 50 monitors the temperature of the first catalyst layer 42, but may be the temperature of the entire first electrode 41. Further, although the control device 50 controls the voltage difference between the first catalyst layer 42 and the second catalyst layer 52, the control device 50 may control the voltage difference between the first electrode 41 and the second electrode 51. The catalyst contained in the first catalyst layer 42 and the second catalyst layer 52 is an alloy of platinum and ruthenium, but any catalyst may be used as long as it causes the reactions of Formulas 1 and 3 respectively.

  Thus, the fuel gas supplied from the CO reduction device 40 to the fuel electrode 82 has a reduced CO concentration. For this reason, the characteristic degradation of the fuel cell 12 and the fuel cell system 71 due to CO poisoning in the catalyst in the fuel electrode 82 can be suppressed, and the characteristics of the fuel cell system 71 can be maintained.

  Further, in the method of mixing oxygen in the fuel gas in order to reduce the CO concentration, if oxygen remains in the fuel gas supplied to the fuel electrode 82, generation of hydrogen peroxide in the fuel electrode 82 becomes a problem. There is a case. However, in the CO reduction device 40 of the present embodiment, oxygen is not mixed in the fuel gas, so that the generation of hydrogen peroxide in the fuel electrode 82 is suppressed. Since the CO concentration in the fuel gas is reduced, a small amount of air that does not accelerate the deterioration of the polymer electrolyte membrane 16 of the fuel cell 12 is additionally supplied to the fuel electrode 82, so that the fuel electrode 82 It is also possible to reduce the CO concentration. Thereby, the characteristics of the fuel cell system 71 can be maintained without accelerating the deterioration of the polymer electrolyte membrane 16.

  In the present embodiment, the CO reduction device 40 has a single-stage configuration, but it may be connected in series to have multiple stages. In this case, the CO concentration in the fuel gas discharged from the CO reduction device 40 is further reduced.

  Further, a plurality of CO reduction devices 40 may be stacked, for example, and fuel gas sent from the reformer may be supplied in parallel to the CO reduction device 40. In this case, the CO reduction device 40 can process more fuel gas.

  In the present embodiment, the controller 50 monitors the temperature of the first electrode 41 and controls the potential difference between the first electrode 41 and the second electrode 51 based on the temperature. However, the potential difference may be fixed. . At that time, the potential difference is set according to the lowest temperature of the first electrode 41 assumed when the fuel cell system 71 is operated. When the minimum temperature is, for example, −20 ° C., the potential of the first electrode 41 with respect to the potential of the second electrode 51 is maintained at 0.5 V or higher from FIG.

  Further, part or all of the CO reduction device 40 may be provided so as to be removable from the fuel cell system 71. For example, a laminated body of the first electrode 41, the second electrode 51, and the polymer electrolyte membrane 17 is provided so as to be removable from the fuel cell system 71. In this case, even if the performance of the CO reduction device 40 is reduced due to deterioration of the catalyst of the first electrode 41 or the second electrode 51, the life of the entire system can be extended by replacing them.

[Second Embodiment]
FIG. 6 is a block diagram of the fuel cell system according to the second embodiment of the present invention.

  The fuel cell system 72 of the present embodiment is obtained by adding an oxidant gas additional supply means to the fuel cell system 71 (see FIG. 2) of the first embodiment. The oxidant gas additional supply means includes an oxidant gas additional supply device 61, a first oxidant gas additional supply pipe 62, and a second oxidant gas additional supply pipe 63. The first oxidant gas additional supply pipe 62 is branched from the middle of the oxidant gas supply pipe 32. The second oxidant gas additional supply pipe 63 is connected to the fuel gas supply pipe 22. The oxidant gas additional supply device 61 is connected to the first oxidant gas additional supply pipe 62 and the second oxidant gas additional supply pipe 63.

The first oxidant gas additional supply pipe 62 sends a part of the air flowing through the oxidant gas supply pipe 32 to the oxidant gas additional supply apparatus 61. The oxidant gas additional supply device 61 adjusts the flow rate of the air and supplies it to the fuel gas supply line 22 via the second oxidant gas additional supply line 63. The flow rate of the air additionally supplied to the fuel gas supply pipe 22 by the oxidant gas additional supply device 61 is controlled by the control device 50. The additionally supplied air flow rate includes oxygen that is (1/2) times the molar ratio of the CO amount contained in the fuel gas before being supplied to the CO reduction device 40, and the air flow rate is reduced by CO. It is made to become less than 25% with respect to the amount of H ₂ contained in the fuel gas before being supplied to the device 40.

In the present embodiment, fuel gas and air are supplied to the first electrode 41 (see FIG. 1) in the CO reduction device 40. CO in the fuel gas reacts with oxygen on the platinum-ruthenium catalyst contained in the first catalyst layer 42 (see FIG. 1) according to Equation 4 to become CO ₂ .

2CO + O ₂ → CO ₂ (Formula 4)
Here, the additionally supplied air flow rate is controlled so as to contain oxygen that is (1/2) times the molar ratio with respect to the CO amount contained in the fuel gas before being supplied to the CO reduction device 40. Therefore, basically, all the CO contained in the fuel gas before being supplied to the CO reduction device 40 becomes CO ₂ . However, CO that does not become CO _{2 in} the reaction of Formula 4 also remains depending on the difference in oxygen amount or the diffusion of CO.

  In the present embodiment, CO that has not caused the reaction of Formula 4 is also electrochemically oxidized according to Formula 1 as in the first embodiment. For this reason, the CO concentration in the fuel gas discharged from the first electrode 41 further decreases.

The CO and the unreacted oxygen that have not reacted in Formula 1 or Formula 4 are reduced according to the following 4-electron reaction represented by Formula 5 or 2-electron reaction represented by Formula 6. Here, it is known that hydrogen peroxide (H ₂ O ₂ ) generated by Equation 6 accelerates polymer film degradation.

O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O (Formula 5)
O ₂ + 2H ⁺ 2e ⁻ → H ₂ O ₂ (Formula 6)
FIG. 7 is a graph showing the ratio of 4-electron reaction and 2-electron reaction to the electrode potential. FIG. 7 shows the case of an electrode using a platinum catalyst for the first catalyst layer 42 and the case of an electrode using a platinum-ruthenium alloy catalyst. The horizontal axis represents the electrode potential relative to the reference electrode (RHE: Reversible Hydrogen Electrode), and the vertical axis represents the ratio of the two-electron reaction shown in Equation 6.

  The higher the two-electron reaction ratio, the more hydrogen peroxide as the product increases, and the deterioration of the polymer electrolyte membrane becomes more remarkable.

  FIG. 7 shows that the two-electron reaction ratio is higher in the low potential region in both the case of the platinum catalyst and the case of the platinum-ruthenium alloy catalyst. In particular, the two-electron reaction rate increases rapidly at 0.1 V or less with respect to the RHE standard. Usually, the electrode potential of the fuel electrode 82 of the fuel cell 12 is 0.1 V or less, that is, when additional air is directly supplied to the fuel electrode 82, the two-electron reaction rate increases and the deterioration of the polymer electrolyte membrane is accelerated.

  On the other hand, the electrode potential of the first electrode 41 of the CO reduction device 40 is maintained at a relatively high potential by the control device 50. For example, when the temperature of the first electrode 41 is 50 ° C., the control device 50 holds the electrode potential of the first electrode 41 at 0.3 V or more with respect to the potential of the second electrode 51. For this reason, the oxygen additionally supplied to the fuel gas undergoes a reduction reaction at 0.3 V in the CO reduction device 40, and therefore the two-electron reaction ratio is smaller than when the oxygen reduction reaction occurs at the fuel electrode 82. Become. Therefore, the deterioration of the polymer electrolyte membrane can be greatly suppressed when the air is additionally supplied to the CO reduction device 40 rather than the additional supply of air to the fuel electrode 82 of the fuel cell 12.

  Thus, the fuel gas supplied from the CO reduction device 40 to the fuel electrode 82 has a reduced CO concentration. For this reason, the characteristic degradation of the fuel cell 12 and the fuel cell system 72 due to CO poisoning in the catalyst in the fuel electrode 82 can be suppressed, and the characteristics of the fuel cell system 72 can be maintained.

  In the present embodiment, since air is not directly supplied to the fuel electrode 82, deterioration of the polymer electrolyte membrane 16 (see FIG. 3) of the fuel cell 21 can be suppressed. In addition, since the electrode potential of the first electrode 41 of the CO reduction device 40 is set to a relatively high potential, the ratio of two-electron reaction occurring on the catalyst in the first catalyst layer 42 is reduced, and the polymer electrolyte of the CO reduction device 40 is reduced. Deterioration of the film 17 is also suppressed. Even if the polymer electrolyte membrane 17 of the CO reduction device 40 is deteriorated, by making the entire CO reduction device 40 or a laminate of the polymer electrolyte membrane 17 and the electrode of the CO reduction device 40 replaceable, The life of the entire system can be extended.

[Other embodiments]
The above-described embodiments are merely examples, and the present invention is not limited to these. Moreover, you may implement combining the characteristic of each embodiment.

1 is a block diagram of a CO reduction device in a first embodiment of a fuel cell system according to the present invention. 1 is a block diagram of a fuel cell system according to a first embodiment of the present invention. It is sectional drawing of the cell in 1st Embodiment of the fuel cell system which concerns on this invention. It is a graph which shows the electrode potential scan at the time of supplying CO to the electrode using a platinum-ruthenium alloy catalyst at 50 degreeC. It is a graph which shows the temperature change of CO oxidation start potential in the electrode using a platinum-ruthenium catalyst. It is a block diagram in 2nd Embodiment of the fuel cell system which concerns on this invention. It is a graph which shows the ratio of 4 electron reaction and 2 electron reaction with respect to electrode potential.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Single cell, 12 ... Fuel cell, 16 ... Polymer electrolyte membrane, 17 ... Polymer electrolyte membrane, 18 ... Power supply, 19 ... Thermometer, 21 ... Fuel gas supply source, 22 ... Fuel gas supply piping, 23 ... Fuel Gas exhaust pipe, 31 ... Oxidant gas supply source, 32 ... Oxidant gas supply pipe, 33 ... Oxidant gas exhaust pipe, 40 ... CO reduction device, 41 ... First electrode, 42 ... First catalyst layer, 43 ... First 1 gas diffusion layer, 44 ... first gas flow path plate, 45 ... first gas pipe, 50 ... control device, 51 ... second electrode, 52 ... second catalyst layer, 53 ... second gas diffusion layer, 54 ... first 2 gas flow path plates, 55 ... second gas pipe, 61 ... oxidant gas additional supply device, 62 ... first oxidant gas additional supply pipe, 63 ... second oxidant gas additional supply pipe, 64 ... intermediate pipe, 71 ... Fuel cell system, 72 ... Fuel cell system, 82 ... Fuel electrode, 83 ... Fuel electrode Medium layer, 84 ... fuel electrode gas diffusion layer, 85 ... fuel electrode gas flow path plate, 87 ... fuel electrode gasket, 88 ... fuel gas flow path, 92 ... oxidant electrode, 93 ... oxidant electrode catalyst layer, 94 ... oxidation Agent electrode gas diffusion layer, 95 ... oxidant electrode gas channel plate, 97 ... oxidant electrode gasket, 98 ... oxidant gas channel

Claims (5)

A fuel cell having a fuel electrode and an oxidant electrode;
A fuel gas supply source for supplying fuel gas to the fuel electrode;
A first gas flow path connected to the fuel gas supply source is formed to contain a catalyst, and a second electrode flow path connected to the fuel electrode is formed to contain a catalyst. A polymer electrolyte membrane sandwiched between the first electrode and the second electrode, an intermediate flow path forming body that forms a flow path connecting the first gas flow path and the second gas flow path, A CO reduction device comprising: a power source for applying a voltage between the first electrode and the second electrode;
A thermometer for measuring the temperature of the CO reduction device;
A control device for controlling the voltage applied by the power source based on the temperature of the CO reduction device;
A fuel cell system comprising: The fuel cell system according to claim 1, further comprising an oxidant gas additional supply device for supplying an oxidant gas to the first gas flow path . The oxidant gas supplying additional devices, fuel cell according to claim 2, characterized in der Rukoto supplies a portion of the oxidant gas supplied to the oxidant electrode to the first gas channel system. A first electrode formed with a first gas flow path to which fuel gas is supplied and containing a catalyst;
A second electrode formed with a second gas flow path connected to the fuel electrode of the fuel cell and containing a catalyst;
A polymer electrolyte membrane sandwiched between the first electrode and the second electrode;
An intermediate flow path forming body that forms a flow path connecting the first gas flow path and the second gas flow path;
A power supply for applying a voltage between the first electrode and the second electrode;
A CO reduction device main body for reducing CO in the fuel gas supplied to the fuel electrode;
A thermometer for measuring the temperature of the CO reduction device main body,
A CO reduction apparatus configured to control a voltage applied from the power source based on a temperature of the CO reduction apparatus main body. A first electrode formed with a first gas flow path to which fuel gas is supplied and containing a catalyst;
A second electrode containing a catalyst in which a second gas flow path is formed in which an upstream side is connected to a downstream side of the first gas flow path and a downstream side is connected to a fuel electrode of a fuel cell ;
A polymer electrolyte membrane sandwiched between the first electrode and the second electrode;
A power supply for applying a voltage between the first electrode and the second electrode;
A CO reduction device main body for reducing CO in the fuel gas supplied to the fuel electrode;
A thermometer for measuring the temperature of the CO reduction device main body,
A CO reduction apparatus configured to control a voltage applied from the power source based on a temperature of the CO reduction apparatus main body.

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