JP2007294366A - Fuel cell system - Google Patents

Abstract

A fuel cell system capable of improving power generation performance over a long period of time is provided.
An electrolyte / electrode structure including an electrolyte layer, an electrode layer disposed on one side of the electrolyte layer, and an electrode layer disposed on the other side, and the electrolyte / electrode structure Current collector 5 disposed on one side of current collector 4, current collector 6 disposed on the other side, and flow paths 7, 8 through which fluid supplied to electrolyte / electrode structure 4 can flow. A fuel cell system in which a liquid is supplied to the flow paths 7 and 8 having a reduced pressure when the operation of the module is stopped.
[Selection] Figure 2

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system capable of improving power generation performance over a long period of time.

  A fuel cell includes a membrane electrode assembly (hereinafter referred to as “the electrolyte membrane”) and electrode layers (anode and cathode) respectively disposed on both sides of the electrolyte membrane. The electrical energy generated by the electrochemical reaction in MEA (Membrane Electrode Assembly) ”) is taken out to the outside through current collectors arranged on both sides of the MEA. Among fuel cells, polymer electrolyte fuel cells (hereinafter referred to as “PEFC (Polymer Electrolyte Fuel Cell)”) used in household cogeneration systems and automobiles, etc., operate at low temperatures. Is possible. In addition, PEFC has attracted attention as an optimal power source for electric vehicles and portable power sources because of its high energy conversion efficiency, short start-up time, and small and lightweight system.

  A single cell of PEFC includes an electrolyte membrane, a cathode and an anode including at least a catalyst layer, and a theoretical electromotive force thereof is 1.23V. In PEFC, a hydrogen-containing gas is supplied to the anode, and an oxygen-containing gas is supplied to the cathode. Hydrogen supplied to the anode is separated into protons and electrons on a catalyst (for example, Pt etc., the same applies hereinafter) contained in the catalyst layer of the anode (hereinafter referred to as “anode catalyst layer”), and from the hydrogen. The generated protons reach the cathode catalyst layer (hereinafter referred to as “cathode catalyst layer”) through the anode catalyst layer and the electrolyte membrane. On the other hand, electrons reach the cathode catalyst layer through an external circuit, and through such a process, electric energy can be extracted. The protons and electrons that have reached the cathode catalyst layer react with oxygen supplied to the cathode catalyst layer on the catalyst, thereby generating water.

  That is, in order to extract electric energy, it is necessary that protons can be conducted through the anode catalyst layer, the electrolyte membrane, and the cathode catalyst layer. From this point of view, the anode catalyst layer, the electrolyte membrane, and the cathode catalyst layer of PEFC are provided with an electrolyte resin having an ion exchange group that can be a passage for protons. The anode catalyst layer and the cathode catalyst layer are provided with metal particles (for example, Pt) that function as a catalyst for an electrochemical reaction, in addition to the electrolyte resin (hereinafter sometimes referred to as “ionomer”). It has been.

  On the other hand, it is becoming clear that hydrogen peroxide is by-produced in the catalyst layer during the operation of PEFC, and radicals generated from this hydrogen peroxide contribute to the degradation of ionomers and the like provided in the MEA. Such deterioration not only reduces the durability of PEFC but also contributes to a decrease in power generation performance. Therefore, it is hoped that reducing the hydrogen peroxide in the MEA will suppress the above deterioration and improve the durability and power generation performance. It is rare.

Several techniques have been disclosed so far with the main purpose of improving the power generation performance of PEFC. For example, Patent Document 1 includes a fuel cell main body including a single cell in which a polymer electrolyte membrane sandwiched between an anode diffusion electrode and a cathode diffusion electrode is further sandwiched between a pair of separators, When the electric power supply is stopped, dilute sulfuric acid is supplied to at least one of a fuel flow path formed on the anode side where fuel is supplied and discharged and an oxidant gas flow path formed on the cathode side where oxidant gas is supplied and discharged Techniques relating to fuel cell systems are disclosed. According to such a technique, dilute sulfuric acid is supplied to at least one of the anode side wetted by humidification of the fuel and the cathode side where water accompanying the cell reaction is present using the fuel flow path or the oxidizing gas flow path. This effectively prevents freezing. As a result, the possibility of stopping power generation during startup can be avoided, the power generation efficiency of the fuel cell can be improved, and the restart after being temporarily stopped can be performed well.
JP 2004-235209 A

  However, even if dilute sulfuric acid is supplied to at least one of the fuel flow path and the oxidizing gas flow path by the technique disclosed in Patent Document 1, if the pressure in the flow path to which dilute sulfuric acid is supplied is high, There is a problem that dilute sulfuric acid is supplied only to the vicinity of the inlet of the flow path, and it is difficult to obtain the effect of preventing freezing and improving the power generation performance.

  Then, this invention makes it a subject to provide the fuel cell system which can improve electric power generation performance over a long time.

In order to solve the above problems, the present invention takes the following means. That is,
The present invention described in claim 1 includes an electrolyte layer, an electrode layer disposed on one side of the electrolyte layer and an electrode layer disposed on the other side, and the electrolyte A current collector disposed on one side of the electrode structure, a current collector disposed on the other side, and a flow path through which a fluid supplied to the electrolyte / electrode structure can flow. The above-described problem is solved by a fuel cell system comprising a module having a single cell and supplying a liquid to a flow path where the pressure is reduced when the operation of the module is stopped.

Here, as a specific example of the “electrolyte layer”, a solid polymer membrane including a polymer having a proton exchange group (ion exchange group functioning as a proton conductor) can be mentioned. Specific examples of the polymer constituting the solid polymer film include a perfluorosulfonic acid polymer and a hydrocarbon polymer.
Further, the “electrode layer” means a layer comprising metal particles that function as a catalyst for electrochemical reaction and an ionomer having proton conductivity. Specific examples of the metal particles are selected from the group consisting of Pt, Co, Ru, Ir, Au, Ag, Cu, Ni, Fe, Cr, Mn, V, Ti, Mo, Pd, Rh, and W. Examples thereof include a Pt alloy having one or two or more metals and Pt. Specific examples of the ionomer include the above-described polymers that can form a solid polymer film.
In addition, as a specific example of the “current collector”, a member (for example, a separator) made of metal, carbon, or the like can be given.
Furthermore, as the “fluid supplied to the electrolyte / electrode structure”, in the case of PEFC, a hydrogen-containing gas and an oxygen-containing gas (for example, air) can be cited, and a direct methanol fuel cell (hereinafter referred to as “DMFC”). In the case of the above), an aqueous methanol solution and an oxygen-containing gas (for example, air) may be mentioned. Hereinafter, the fluid supplied to the electrolyte / electrode structure may be referred to as “reaction fluid”.
Furthermore, in the present invention, the current collector and the flow path are not particularly limited as long as the current collector and the flow path are provided in a form capable of operating the fuel cell system of the present invention for a long time. It is also possible to adopt a form in which the body is provided with a flow path. In the present invention, the “flow path” is a concept including a flow path provided in a single cell (for example, a flow path provided in a current collector) and a flow path provided outside the single cell.
In addition, “when the operation of the module is stopped” means that the reaction fluid for operating the module including the single cell is not supplied to the flow path. In addition, the “flow path with reduced pressure” means, for example, that the reaction fluid supplied to the anode passes through the electrolyte layer and reaches the anode side, and / or the reaction fluid supplied to the cathode passes through the electrolyte layer. A state in which the pressure of the flow path in the single cell that has been kept airtight by the seal member or the like is reduced by passing through and reaching the cathode side (for example, a state in which the pressure is reduced to a pressure below atmospheric pressure) Means.
Further, specific examples of the “liquid” supplied to the flow path when the operation of the module is stopped include a liquid containing ions having hydrogen peroxide decomposition performance and a liquid having a freezing suppression function, which will be described later. . Specific examples of the liquid containing ions having the ability to decompose hydrogen peroxide include an aqueous solution containing the ions. On the other hand, specific examples of the liquid having the freeze-inhibiting function include ethanol, methanol, a fluorine-based antifreeze liquid, and the like in addition to a liquid containing ethylene glycol.

  According to a second aspect of the present invention, in the fuel cell system according to the first aspect, the liquid includes ions having hydrogen peroxide decomposition performance.

Specific examples of the “ion having hydrogen peroxide decomposition performance” include transition metal ions, rare earth metal ions, and the like. Specifically, C ⁴⁺ , Si ⁴⁺ , Sc ³⁺ , Ti ⁴⁺ , Mn ²⁺ , Co ²⁺ , Cu ²⁺ , Se ²⁺ , Rb ⁺ , Y ³⁺ , Zr ⁴⁺ , Nb ⁵⁺ , Rh ²⁺ , Pd ⁺ , Ag ⁺ , Sn ²⁺ , La ³⁺ , Ce ⁴⁺ , Pr ³⁺ , Nd ^{3 +} , Sm3 ⁺ , Eu3 ⁺ , Gd3 ⁺ , Tb3 ⁺ , Dy3 ⁺ , Ho3 ⁺ , Er3 ⁺ , Tm3 ⁺ , Yb3 ⁺ , Lu3 ⁺ , Hf4 ⁺ , ^{Ta5 +} , Os4 ⁺ , Ir2 ⁺ , t2 ⁺ Illustrated.

  According to a third aspect of the present invention, in the fuel cell system according to the second aspect, the ions having hydrogen peroxide decomposition performance are Ce ions.

  According to the present invention, since the liquid is supplied to the flow path where the pressure is reduced, it is possible to supply the liquid uniformly not only to the vicinity of the inlet of the flow path but also to the entire flow path and the MEA. Therefore, for example, when the liquid is a liquid containing ions having hydrogen peroxide decomposition performance (hereinafter referred to as “decomposed ions”), the decomposed ions contained in the liquid are uniformly supplied to the MEA. Further, the durability of the MEA can be improved, and a fuel cell system that can improve the power generation performance can be provided. Further, when the liquid is a liquid having a freeze-inhibiting function (hereinafter sometimes referred to as “freezing-inhibiting agent”), the anti-freezing agent can be uniformly supplied to the flow path and the MEA. As a result, freezing of the liquid (for example, water) remaining in the flow path and the MEA is prevented, and the low temperature startability can be improved. As a result, a fuel cell system that can improve power generation performance can be provided. In addition, according to the present invention, the liquid can be supplied to the flow path where the pressure is reduced every time the operation of the module is stopped, so that the power generation performance can be improved over a long period of time. Can provide.

  During the operation of PEFC, water is generated from hydrogen and oxygen, and hydrogen peroxide is by-produced. The ionomer and the like in the MEA are deteriorated by OH radicals, OOH radicals and the like generated from the hydrogen peroxide, and the power generation performance and durability of the PEFC are lowered. Therefore, in order to improve the power generation performance and durability of PEFC, it is effective to decompose hydrogen peroxide produced as a by-product, and a substance having hydrogen peroxide decomposition performance (hereinafter, referred to as “decomposition substance”). )), Rare earth metal ions and the like are known. In the past, PEFCs with a form of a decomposition substance have been proposed for the purpose of decomposing hydrogen peroxide, etc., but since the decomposition substance elutes during the operation of PEFC, the hydrogen peroxide decomposition effect is prolonged. Hard to last over time. In view of this, a fuel cell system has been proposed that can supply a decomposition material to the MEA. However, the present inventor has found that when the pressure at the location (flow path, MEA, etc.) to which the decomposition substance is supplied is high, the decomposition substance is hardly supplied uniformly and it is difficult to improve the power generation performance and durability. In order to supply the decomposed material uniformly to the MEA, it is effective to supply the decomposed material to the flow path and the MEA where the pressure is reduced.

  The present invention has been made from such a viewpoint, and the gist of the present invention is to supply a liquid (a liquid containing a decomposition substance, a freeze inhibitor, etc.) to a flow path whose pressure has been reduced, thereby generating power over a long period of time. It is an object of the present invention to provide a fuel cell system capable of improving the fuel efficiency.

  Hereinafter, the fuel cell system of the present invention will be described more specifically with reference to the drawings. Unless otherwise specified, a case where the present invention is applied to a fuel cell system including a PEFC will be described. However, the present invention is not limited to a fuel cell including a solid polymer film as an electrolyte layer. (For example, it is applicable also to a fuel cell system provided with DMFC).

1. First Embodiment FIG. 1 is a schematic view showing a fuel cell system of the present invention according to a first embodiment. In FIG. 1, arrows indicate the flow direction of an oxygen-containing gas (hereinafter referred to as “air”) or a hydrogen-containing gas (hereinafter referred to as “hydrogen”).

  As shown in FIG. 1, the fuel cell system 100 according to the first embodiment of the present invention includes a liquid supply capable of supplying a liquid to a fuel cell module 10 and a single cell (see FIG. 2) provided in the fuel cell module 10. And means 20. The fuel cell module 10 (hereinafter referred to as “FC module 10”) includes a first intake line 41 and a first exhaust line 42 through which mainly air flows, a hydrogen supply line 43 and a hydrogen recovery line 44 through which hydrogen flows. And are connected. On the other hand, the liquid supply means 20 includes a liquid supply line 45 through which the liquid supplied to the single cell should flow, a liquid recovery line 46 through which the liquid recovered from the single cell should flow, and when supplying the liquid to the single cell. The second intake line 47 and the second exhaust line 48 used in the above are connected. Then, the liquid supply line 45 is connected to the first intake line 41 and the liquid recovery line 46 is connected to the first exhaust line 42, so that the liquid supply from the liquid supply means 20 to the single cell and the single cell The liquid supply means 20 is configured to be able to recover the liquid. Further, the first intake line 41, the first exhaust line 42, the hydrogen supply line 43, the hydrogen recovery line 44, the liquid supply line 45, the liquid recovery line 46, the second intake line 47, and the second exhaust line 48 include: Valves 31, 32, 33, 34, 35, 36, 37, and 38 that can adjust the flow rate of the gas or liquid flowing through these are provided.

  During operation of the FC module 10, air is supplied to the FC module 10 via the first intake line 41 and hydrogen is supplied to the FC module 10 via the hydrogen supply line 43. Then, the air passing through the FC module 10 is discharged out of the FC module 10 via the first exhaust line 42, and the hydrogen passing through the FC module 10 is recovered via the hydrogen recovery line 44. In this case, valves 31, 32, 33, and 34 are open, and valves 35, 36, 37, and 38 are closed. On the other hand, the liquid supply means 20 is provided with a liquid to be supplied to a single cell in the FC module 10 when the FC module 10 is stopped. When the inside of the FC module 10 is in a decompressed environment after the FC module 10 is stopped, the single cell of the FC module 10 is supplied from the liquid supply means 20 as necessary (for example, when the amount of decomposition substances provided in the single cell is reduced). Liquid is supplied to When the liquid is supplied from the liquid supply means 20 to the single cell, the valves 31, 32, 33, and 34 are closed and then the valves 35, 36, 37, and 38 are opened as will be described later. . Thus, when the valves 35, 36, 37, and 38 are opened, the liquid is supplied to the single cell provided in the FC module 10 through the liquid supply line 45 and the first intake line 41, for example, After the flow path and MEA in the single cell are filled with the liquid, the liquid is recovered to the liquid supply means 20 via the first exhaust line 42 and the liquid recovery line 46. When the recovery of the liquid from the single cell to the liquid supply means 20 is completed, the valves 35, 36, 37, and 38 are closed. Thereafter, when the operation of the FC module 10 is resumed, the valves 31, 32, 33 are used. , And 34 are opened.

  FIG. 2 is a cross-sectional view showing an example of a single cell provided in the FC module 10, and shows only a part of the single cell. As shown in FIG. 2, the single cell 9 includes an electrolyte membrane 1, an anode catalyst layer 2a disposed on one side of the electrolyte membrane 1, a cathode catalyst layer 3a disposed on the other side, and an anode catalyst. An anode diffusion layer 2b disposed on the layer 2a side, a cathode diffusion layer 3b disposed on the cathode catalyst layer 3a side, a separator 5 disposed on the anode diffusion layer 2b side, and a cathode diffusion layer 3b side And a separator 6 disposed. The anode 2 includes an anode catalyst layer 2a and an anode diffusion layer 2b, the cathode 3 includes a cathode catalyst layer 3a and a cathode diffusion layer 3b, and the MEA 4 includes an anode catalyst layer 2a, an electrolyte membrane 1, and a cathode catalyst layer. 3a. The electrolyte membrane 1 includes an ionomer such as a perfluorosulfonic acid polymer, and the anode catalyst layer 2a and the cathode catalyst layer 3a include the ionomer and a catalyst such as platinum supported on carbon. It is done. Further, the separator 5 is provided with flow paths 7, 7,..., And the separator 8 is provided with flow paths 8, 8,. Hereinafter, the fuel cell system 100 of the present invention will be described with reference to FIGS. 1 and 2.

When the FC module 10 is operated, hydrogen is supplied to the anode 2 via the hydrogen supply line 43 and the flow paths 7, 7,. The hydrogen that has reached the anode catalyst layer 2a of the anode 2 becomes protons and electrons on the catalyst provided in the anode catalyst layer 2a, and the protons thus generated are converted into the anode catalyst layer 2a, the electrolyte membrane 1, and the cathode catalyst layer. It reaches the catalyst provided in the cathode catalyst layer 3a through the ionomer provided in 3a. On the other hand, electrons reach the catalyst of the cathode catalyst layer 3a through an external circuit. On the other hand, when the FC module 10 is operated, air is supplied to the cathode 3 through the first intake line 41 and the flow paths 8, 8,. When oxygen contained in the air reaches the catalyst of the cathode catalyst layer 3a provided in the cathode 3, water is generated by reacting with protons and electrons that have moved from the anode catalyst layer 2a. As described above, while the FC module 10 is operated, water is generated, while hydrogen peroxide is generated by a side reaction of the water generation reaction, and OH radicals, OOH radicals, and the like are generated from the hydrogen peroxide. . These OH radicals, OOH radicals, and the like can degrade the ionomer, as well as the anode diffusion layer, the cathode diffusion layer, the separator, and the like. Therefore, in order to suppress deterioration of each member constituting the single cell, it is effective to decompose hydrogen peroxide which is a generation source of OH radicals and OOH radicals. From this point of view, in the fuel cell system 100, after the pressure of the flow paths 8, 8,... In the stopped FC module 10 decreases, for example, liquid (Ce) containing a decomposition substance is transferred from the liquid supply means 20 to the single cell 9. An aqueous solution containing ions). Hereinafter, a mode in which Ce ions (for example, Ce ⁴⁺ ) are supplied to the single cell 9 will be described.

  As described above, when the FC module 10 is operated, hydrogen is supplied to the anode 2 and air is supplied to the cathode 3, and water and oxygen are reacted to generate water. Here, after supplying hydrogen and air to the FC module 10, when the closed spaces are formed by closing the valves 31, 32, 33, and 34, the hydrogen and oxygen remaining in the single cell 9 cause the electrolyte membrane 1 to pass through. Permeates (crosses over) and reacts to produce water. When water is generated in this way, the amount of residual gas in the single cell 9 is reduced, so that the single cell 9, the first intake line 41, the first exhaust line 42, the hydrogen supply line 43, and hydrogen The recovery line 44 becomes a reduced pressure environment. After the reduced pressure environment is formed in this manner, when the valves 35, 36, 37, and 38 are opened and the liquid is supplied from the liquid supply means 20, the liquid supply line 45, the first intake line 41, and the flow path The liquid reaches the cathode diffusion layer 3b via 8, 8,... And the pressure of the MEA 4 in the single cell 9 is reduced, so that the liquid becomes the cathode catalyst layer 3a, the electrolyte membrane 1, and the anode. The catalyst layer 2a (hereinafter collectively referred to as “MEA4”) is supplied uniformly. When the liquid is supplied to the MEA 4 in this manner, protons of proton exchange groups provided in the ionomer in the MEA 4 and Ce ions provided in the liquid are ion-exchanged, and Ce ions are taken into the MEA 4.

  Note that when liquid is supplied to a single cell that is not in a reduced pressure environment as in the prior art, gas remains in the pores of the cathode diffusion layer and anode diffusion layer after the FC module is stopped. It is difficult to pass through the cathode diffusion layer and the anode diffusion layer. For this reason, it is difficult to uniformly supply the liquid to the MEA, and the liquid is likely to be supplied unevenly. If the liquid is supplied in a non-uniform manner in this way, the ion exchange is performed only at the site where the liquid is supplied, so that the ion exchange at the site proceeds excessively, and the proton conduction performance deteriorates and the power generation performance decreases. There is a problem of doing. According to the present invention, since the liquid is supplied to the MEA in a reduced pressure environment, such a problem can be solved.

  After the supply of the liquid to the single cell 9 is completed and the liquid is recovered to the liquid supply means 20, when the FC module 10 is operated again, hydrogen peroxide is by-produced in the single cell 9. However, according to the fuel cell system 100, when the FC module 10 is stopped, Ce ions having hydrogen peroxide decomposition performance are supplied to the MEA 4, so that the by-produced hydrogen peroxide can be decomposed. Thus, if hydrogen peroxide is decomposed, it becomes possible to prevent the generation of OH radicals, OOH radicals, etc. that degrade the ionomer and the like and reduce the power generation performance and durability. The fuel cell system 100 that can improve the power generation performance and durability can be provided.

  If the operation of the FC module 10 is continued, Ce ions are eluted with the passage of time, and the hydrogen peroxide decomposition performance is lowered, and the power generation performance of the FC module 10 may be lowered. However, according to the present invention, since the liquid can be supplied to the FC module 10 that has been in a reduced pressure environment after the stop, for example, the liquid can be supplied every time the operation of the FC module 10 is stopped. Therefore, according to the present invention, Ce ions can be repeatedly added, so that the fuel cell system 100 capable of improving the power generation performance and durability over a long period of time can be obtained.

  FIG. 3 is a schematic diagram showing an example of the form of the liquid supply means 20 provided in the fuel cell system 100, and arrows indicate the moving directions of the liquid flowing through the liquid supply means 20. In FIG. 3, the same reference numerals as those used in FIG. 1 are assigned to the same components as those shown in FIG. 1, and description thereof will be omitted as appropriate. Hereinafter, the fuel cell system 100 of the present invention will be described with reference to FIGS.

  As shown in FIG. 3, the liquid supply means 20 is recovered to the return liquid tank 21 into which the recovered liquid should flow, the liquid feed line 22 as a liquid flow path in the liquid supply means 20, and the return liquid tank 21. An ion detection means 23 capable of detecting the ion concentration of the liquid, a liquid feed pump 24, an electrodialysis cell 25 having an ion concentration detection function, a high concentration solution tank 26 having a high concentration Ce ion solution, and a Ce ion concentration. And an adjustment liquid tank 27 for storing the adjusted adjustment liquid, and an ion removal means 28 is provided at the inlet of the return liquid tank 21 (= the outlet of the liquid recovery line 46; the same applies hereinafter). The return liquid tank 21 is connected to the liquid recovery line 46 and the second exhaust line 48, and the adjustment liquid tank 27 is connected to the liquid supply line 45 and the second intake line 47. A replenishment port (not shown) used when replenishing liquid (for example, deionized water) to the return liquid tank 21 is provided.

  According to the liquid supply means 20 of such a form, it is added from the high concentration solution tank 26 via the electrodialysis cell 25 by adjusting the electroosmotic conditions based on the ion concentration detected by the ion detection means 23. The amount of high concentration solution can be adjusted. Therefore, the Ce ion concentration of the adjustment liquid stored in the adjustment liquid tank 27 can be easily controlled. When supplying the liquid (adjustment liquid) to the single cell 9, the adjustment liquid stored in the adjustment liquid tank 27 is supplied to the single cell 9 via the liquid supply line 45 to operate the FC module 10. Prior to restarting, the liquid is recovered via the liquid recovery line 46.

  As shown in FIG. 3, the liquid supply means 20 includes an ion removing means 28 at the inlet of the return liquid tank 21. Therefore, according to the liquid supply means 20, ions (for example, Fe ions, Cr ions, Ni ions, Al ions, etc., which are mixed in a small amount in the liquid recovered via the liquid recovery line 46 and deteriorate ionomers, etc.) , "Impurity ions"). If the impurity ions are removed in this way, it is possible to prevent the power generation performance and durability of the FC module 10 from being deteriorated by the impurity ions, so that the power generation performance and durability can be further improved.

  Here, for example, when the fuel cell system 100 is provided in an automobile, the power of the liquid feeding pump 24 and the electrodialysis cell 25 can be obtained from the FC module 10 and / or a secondary battery provided in the automobile. . In this case, it is preferable to obtain the power of the liquid feed pump 24 and the electrodialysis cell 25 during the operation of the FC module 10 and adjust the adjustment liquid during the operation of the FC module 10.

  In FIG. 3, the liquid supply is provided with a return liquid tank 21, a liquid feed line 22, an ion detection means 23, a liquid feed pump 24, an electrodialysis cell 25, a high concentration solution tank 26, and an ion removal means 28. Although the means 20 is illustrated, the liquid supply means according to the fuel cell system of the present invention may be in a form in which these are not provided. However, from the viewpoint of reducing the environmental load, the circulation path of the liquid is preferably a circulatory line. When the circulatory line is used, the return liquid tank, the liquid feed line, the ion detection means, Preferably, a liquid pump and a high concentration solution tank are provided. Further, from the viewpoint of further improving the power generation performance and durability, it is preferable that the ion removing means is provided. A specific example of the ion removing means 28 provided in the liquid supply means 20 includes an ion exchanger provided with a cation exchange resin.

  In addition, FIG. 3 exemplifies the liquid supply means 20 that is incorporated in the circulation system line and adjusts the liquid (conditioning liquid). However, the liquid supply means according to the fuel cell system of the present invention is not limited to this form. It is not limited to. As another form example that the liquid supply means can take, there can be mentioned a form in which the liquid supply means is provided with a container having a preliminarily adjusted liquid before the liquid supply means is operated. In the case of such a form, for example, after the adjustment liquid in the container is exhausted, the container is replaced with another container having an adjustment liquid whose Ce ion concentration is adjusted. The fuel cell system can improve the power generation performance and durability. In the case of the liquid supply means 20 according to the embodiment shown in FIG. 3, from the viewpoint of improving the handleability, it is preferable that the high concentration solution tank 26 is a cartridge type and can be replaced.

  Further, in FIG. 3, the liquid supply means 20 in the form in which the electrodialysis cell 25 is provided is illustrated, but the liquid supply means in the fuel cell system of the present invention may be in a form in which the electrodialysis cell 25 is not provided. good. In this case, the adjustment liquid can be adjusted by adopting a form in which the high concentration solution is periodically supplied from the high concentration solution tank 26 to the liquid feeding line 22. However, from the viewpoint of facilitating the control of the Ce ion concentration of the liquid supplied to the single cell 9, it is preferable to use the liquid supply means 20 in a form in which the electrodialysis cell 25 is provided.

  In addition, in the above description, deionized water is exemplified as the liquid to be supplied to the return liquid tank 21, but the present invention is not limited to such a form. However, it is preferable to use deionized water as the liquid to be replenished from the viewpoint of providing the fuel cell system 100 that easily improves the power generation performance and durability by replenishing the liquid that does not contain impurity ions.

  In the above embodiment in which Ce ions are supplied to the single cell, the amount of Ce ions supplied to the single cell is not particularly limited. However, from the standpoint of developing hydrogen peroxide decomposition performance, etc., the amount is such that 0.1% or more of protons of proton exchange groups provided in the MEA of a single cell supplied with liquid are ion-exchanged by Ce ions. It is preferable. Moreover, from the viewpoint of suppressing a decrease in proton conduction performance due to excessive ion exchange by Ce ions, the ratio of proton exchange group protons provided in the single cell MEA is 95% or less. It is preferable to do. A more preferable amount of liquid is an amount in which 0.3% to 10% of protons are ion-exchanged by Ce ions. In addition, also when decomposition ions other than Ce ions are supplied to the single cell, from the same viewpoint, the amount of the decomposition ions is 0.1% or more and 95% of protons of the proton exchange group provided in the MEA of the single cell. The following are preferably ion exchanged amounts.

  In the fuel cell system 100 of the present invention, the concentration overvoltage value of the FC module 10 can be exemplified as an index for determining whether or not to supply liquid. For example, when the concentration overvoltage of the FC module 10 is measured by AC impedance measurement and the value of the concentration overvoltage exceeds a threshold value, an amount of hydrogen peroxide that causes degradation of ionomer in the single cell is generated, or Recognizing that the amount of Ce ions in the single cell has decreased, it can be determined that it is time to supply Ce ions. When it is determined that the Ce ion should be supplied in this way, the liquid is supplied from the liquid supply means to the single cell when the FC module 10 is stopped for the first time and a reduced pressure environment is formed. It ’s fine. In addition, by investigating the power generation performance according to the operating environment and operating time of the FC module 10 in advance, it is possible to grasp the time when Ce ions should be supplied, and from the liquid supply means to the single cell each time the time comes. It is also possible to supply liquid to

FIG. 4 is a flowchart schematically showing an operation procedure of the fuel cell system 100. Hereinafter, the operation procedure of the fuel cell system 100 will be described with reference to FIGS.
In the fuel cell system 100 of the present invention, it is determined whether or not to supply liquid to the single cell 9 after the FC module 10 is stopped (step S1). When an affirmative determination is made in step S1, the valves 31, 32, 33, and 34 are closed to form a closed space (step S2). When the closed space is formed in this way, hydrogen and oxygen remaining in the closed space permeate through the electrolyte membrane 1 to react with each other, so that the pressure of the single cell 9 is lowered. Is determined (step S3). Here, as a method for determining whether or not the environment is a reduced pressure environment, in addition to a method for determining whether or not the measured value of the pressure gauge capable of measuring the fluid pressure in the single cell 9 is reduced to the atmospheric pressure or lower, it is set in advance. A method for determining whether or not the pressure has become lower than the predetermined pressure or whether or not a preset time has elapsed can be exemplified. If an affirmative determination is made in step S3, it can be determined that the closed space has been depressurized and an environment in which liquid can be supplied uniformly has been formed, so that the valve 37 is used to supply liquid from the liquid supply means 20 to the single cell 9. Then, the valve 35 is opened (step S4), the valve 38 and the valve 36 are opened (step S5), and the supply of liquid is started. Thereafter, when time elapses, the MEA 4 of the single cell 9 is filled with the liquid, and therefore it is determined whether or not the liquid supply should be terminated (step S6). If an affirmative determination is made in step S6, the MEA 4 is filled with the liquid, so that the valve 36 and the valve 38 are closed after the valve 37 and the valve 35 are closed (step S7). Thereafter, the MEA 4 is allowed to stand for a certain period of time while being filled with the liquid, whereby protons of proton exchange groups provided in the ionomer of the MEA 4 are ion-exchanged by Ce ions, and the Ce ions are taken into the ionomer of the MEA 4 (Step S8). ). When the Ce ions are taken into the MEA 4, the valves 38, 36, and 31 are opened to recover the liquid to the liquid supply means 20, and the liquid is recovered to the return liquid tank 21 of the liquid supply means 20 (step S9). . Thereafter, it is determined whether or not the liquid recovery has been completed (step S10). If an affirmative determination is made in step S10, the valves 31, 36 and 38 are closed (step S11), and the liquid supply means 20 The liquid supply / recovery process ends.

  On the other hand, if a negative determination is made in step S1, no liquid is supplied from the liquid supply means 20 to the single cell 9, so that the liquid supply / recovery process by the liquid supply means 20 is not performed. If a negative determination is made in step S3, since the formation of the reduced pressure environment has not been completed, it is maintained until the reduced pressure environment is formed. Further, when a negative determination is made in step S6, the MEA 4 is not yet filled with the liquid and the supply of the liquid needs to be continued, so that the valves 35, 36, 37, and 38 are kept open. Is done. In addition, when a negative determination is made in step S10, it is considered that the unrecovered liquid remains in the single cell 9, so that the valves 31, 36, and 38 are set to continue the liquid recovery process. The open state is maintained.

FIG. 5 is a flowchart schematically showing an operation procedure of the liquid supply means 20 provided in the fuel cell system 100. Hereinafter, the operation procedure of the liquid supply means 20 will be described with reference to FIGS.
In order to operate the liquid supply means 20, first, it is necessary to prepare a liquid that is first supplied from the liquid supply means 20 to the single cell 9. Here, the liquid is preferably deionized water from the viewpoint of making it difficult for the impurity ions that reduce power generation performance to be supplied to the FC module 10. Therefore, deionized water is supplied to the return liquid tank 21 of the liquid supply means 20 before the operation of the liquid supply means 20 (step S21). For example, during operation of the FC module 10, the liquid feed pump 24 is activated (step S22), and the electrodialysis cell 25 is activated (step S23). When the liquid feed pump 24 and the electrodialysis cell 25 are operated in this way, the high concentration Ce ions in the high concentration solution tank 26 are passed through the electrodialysis cell 25 to the deionized water flowing in the liquid feed line 22. By supplying the solution, the adjustment liquid is adjusted, and the adjustment liquid is stored in the adjustment liquid tank 27 (step S23). Then, after the adjustment liquid is stored, when the valves 35, 36, 37, and 38 are opened by the steps S4 and S5, the supply of the liquid is started (step S24). Thereafter, when an affirmative determination is made in step S6, the supply of the liquid to the single cell 9 is stopped (step S25), and there is no need to adjust the adjustment liquid supplied to the single cell 9. Therefore, the electrodialysis cell 25 is stopped (step S26), and the liquid feed pump 24 is further stopped (step S27). After the electrodialysis cell 25 and the liquid feed pump 24 are stopped in this way, when the ion exchange in step S8 is completed, the liquid that has filled the single cell 9 is collected into the return liquid tank 21 (step S28). When the recovery of the liquid ends (step S29), the liquid supply / recovery process by the liquid supply means 20 ends.

2. Second Embodiment FIG. 6 is a schematic view showing a fuel cell system of the present invention according to a second embodiment, and arrows indicate the flow direction of air or hydrogen. In FIG. 6, the same reference numerals as those used in FIG. 1 are assigned to the same components as those shown in FIG. 1, and description thereof will be omitted as appropriate. Hereinafter, the fuel cell system according to the second embodiment of the present invention will be described with reference to FIGS. 2 and 6.

  As shown in FIG. 6, the fuel cell system 200 of the present invention according to the second embodiment includes an FC module 10 and a liquid supply means 20 that can supply a liquid to the single cell 9 provided in the FC module 10. I have. The FC module 10 is connected to a first intake line 41 and a first exhaust line 42 through which mainly air flows, and a hydrogen supply line 43 and a hydrogen recovery line 44 through which hydrogen flows. On the other hand, the liquid supply means 20 supplies the liquid to the single cell 9 with the liquid supply line 45 through which the liquid supplied to the single cell 9 should flow, the liquid recovery line 46 through which the liquid recovered from the single cell 9 should flow. A second intake line 47 and a second exhaust line 48 used when supplying are connected. The liquid supply line 45 is connected to the first intake line 41, and the liquid recovery line 46 is connected to the first exhaust line 42, so that the liquid supply from the liquid supply means 20 to the single cell 9 and the single cell The liquid can be recovered from 9 to the liquid supply means 20. Further, the first intake line 41, the first exhaust line 42, the hydrogen supply line 43, the hydrogen recovery line 44, the liquid supply line 45, the liquid recovery line 46, the second intake line 47, and the second exhaust line 48 include: Valves 31, 32, 33, 34, 35, 36, 37, and 38 that can adjust the flow rate of the gas or liquid flowing through these are provided. In addition to the above configuration, a decompression pump 50 is further connected to the first exhaust line 42 of the fuel cell system 200 via a decompression line 52 and a valve 51. Specific examples of the decompression pump 50 provided in the fuel cell system 200 include a vacuum pump.

As described above, the fuel cell system 200 includes the decompression pump 50. Therefore, after the FC module 10 is stopped, the pressure in the reduced pressure environment formed by the reaction of hydrogen and oxygen remaining in the closed space can be more reliably reduced using the reduced pressure pump 50. Therefore, according to the fuel cell system 200 according to the second embodiment, the pressure of the flow paths 8, 8,...
It is possible to supply to the power source uniformly, and the power generation performance can be improved.

  FIG. 7 is a flowchart schematically showing an operation procedure of the fuel cell system 200. Hereinafter, an operation procedure of the fuel cell system 200 when a liquid containing Ce ions is supplied to the single cell 9 will be described with reference to FIGS. 2, 3, 6, and 7.

  In the fuel cell system 200 of the present invention, it is determined whether or not to supply liquid to the single cell 9 after the FC module 10 is stopped (step S31). If an affirmative determination is made in step S31, the valves 31, 32, 33, and 34 are closed to form a closed space (step S32). When the closed space is formed in this way, hydrogen and oxygen remaining in the closed space permeate through the electrolyte membrane 1 to react, thereby reducing the pressure of the single cell 9. Here, in the fuel cell system 200, the pressure reducing pump 50 is operated after step S32 in order to reduce the pressure in the closed space more reliably (step S33), and then the valve 51 is opened to thereby reduce the pressure reducing pump. 50 is used to further reduce the pressure in the closed space (step S34). Then, it is determined whether or not the decompression is completed (step S35). Here, as a method of determining whether or not the pressure reduction is completed, whether or not the measured value of the pressure gauge capable of measuring the pressure in the single cell 9 has decreased to a pressure of 0.1 [MPa (abs)] or less. In addition to the method of determining by the above, examples include a method of determining whether or not a preset time has elapsed since the start of the operation of the pressure reducing pump 50, or whether or not the pressure is lower than a preset pressure. The If an affirmative determination is made in step S35, it can be determined that the closed space has been sufficiently decompressed and an environment in which liquid can be supplied uniformly has been formed. Therefore, after the valve 51 is closed (step S36), the operation of the decompression pump 50 is stopped (step S37). Thereafter, in order to supply the liquid from the liquid supply means 20 to the single cell 9, the valve 37 and the valve 35 are opened (step S38), and further the valve 38 and the valve 36 are opened (step S39). Be started. When the supply of the liquid starts, the time elapses, and the MEA 4 of the single cell 9 is filled with the liquid. Therefore, it is determined whether or not the supply of the liquid should be terminated (step S40). If an affirmative determination is made in step S40, the MEA 4 is filled with the liquid, so that the valve 36 and the valve 38 are closed after the valve 37 and the valve 35 are closed (step S41). Thereafter, the MEA 4 is left for a certain period of time while being filled with the liquid, whereby protons of proton exchange groups provided in the ionomer of the MEA 4 are ion-exchanged by Ce ions, and the Ce ions are taken into the ionomer of the MEA 4 (Step S42). ). When the Ce ions are taken into the MEA 4, the valves 38, 36, and 31 are opened to recover the liquid to the liquid supply means 20, and the liquid is recovered to the return liquid tank 21 of the liquid supply means 20 (step S43). . Thereafter, it is determined whether or not the liquid recovery has been completed (step S44). If an affirmative determination is made in step S44, the valves 31, 36 and 38 are closed (step S45), and the liquid supply means 20 The liquid supply / recovery process ends.

  On the other hand, if a negative determination is made in step S31, no liquid is supplied from the liquid supply means 20 to the single cell 9, so that the liquid supply / recovery process by the liquid supply means 20 is not performed. Further, when a negative determination is made in step S35, the pressure in the closed space has not been sufficiently lowered, and thus the pressure is maintained as it is until sufficient pressure reduction is performed. Further, when a negative determination is made in step S40, the MEA 4 is not yet filled with the liquid and it is necessary to continue the supply of the liquid, so that the valves 35, 36, 37, and 38 are kept open. Is done. In addition, when a negative determination is made in step S44, it is considered that the unrecovered liquid remains in the single cell 9, so that the valves 31, 36, and 38 are set to continue the liquid recovery process. The open state is maintained.

In the above description, the form in which the liquid containing Ce ions is supplied to the single cell is exemplified, but in the present invention, when the liquid containing the decomposition ions is supplied to the single cell, the decomposition ions provided in the liquid are: It is not limited to Ce ions. As decomposition ions, C ⁴⁺ , Si ⁴⁺ , Sc ³⁺ , Ti ⁴⁺ , Mn ²⁺ , Co ²⁺ , Cu ²⁺ , Se ²⁺ , Rb ⁺ , Y ³⁺ , Zr ⁴⁺ , Nb ⁵⁺ , Rh ²⁺ , Pd ⁺ , Ag ⁺ , ^{sn 2+, La 3+, Ce 4+} , Pr 3+, Nd 3+, Pm 3+, Sm 3+, Eu 3+, Gd 3+, Tb 3+, Dy 3+, Ho 3+, Er 3+, Tm 3+, Yb 3+, Lu 3+, Hf 4+ , Ta ⁵⁺ , Os ⁴⁺ , Ir ²⁺ , Pt ²⁺ , Au ^{+ and the} like.

  In the above description, the liquid containing the decomposition ions is mainly supplied to the single cell. However, in the fuel cell system of the present invention, the liquid having the freeze suppression function may be supplied to the single cell. . Examples of the liquid having a freeze-inhibiting function include ethanol, methanol, a fluorine-based antifreeze liquid, and the like in addition to a liquid containing ethylene glycol. According to the present invention, the liquid is supplied to the single cell whose pressure has decreased after the FC module is stopped. Therefore, it is necessary to discharge the water remaining in the FC module after stopping in order to improve the low temperature startability, unlike the conventional technology that scavenges and discharges water by supplying air to a single cell whose pressure has dropped. There is no. Here, the anode, the electrolyte membrane, and the cathode included in the single cell of PEFC are made of a material having air permeability, and the air permeability is ensured by a large number of pores. The water in the single cell after stopping the FC module is thought to remain in these pores. However, it is difficult to discharge the water remaining in the pores outside the single cell with the conventional technology, and the effect of improving low temperature startability It was difficult to obtain. However, according to the present invention, since the freezing inhibitor can be supplied to the single cell without scavenging the single cell whose pressure has decreased, the freezing inhibitor can be diffused into the pores. Therefore, if the freezing inhibitor is supplied to the single cell whose pressure has decreased, it is possible to provide a fuel cell system that can improve the cold startability.

  In the present invention, when supplying the liquid after decompression, when the MEA is filled with the liquid, the pressure is applied to the flow path in the single cell and the MEA via the liquid supply line and the first intake line. Also good. In this way, since it becomes easier to diffuse the liquid into the MEA, the power generation performance and durability, or the low-temperature startability can be further improved. In the above description, the liquid supply line is connected to the first intake line and the liquid recovery line is connected to the first exhaust line. However, the present invention is not limited to this form. The liquid supply line may be connected to the hydrogen supply line, and the liquid recovery line may be connected to the hydrogen recovery line.

  In the above description, the fuel cell in which the anode and the cathode are provided with the diffusion layer is illustrated, but the fuel cell to which the present invention is applicable is not limited to the embodiment, and the anode and / or the cathode is provided with the diffusion layer. It is also possible to have no form. Moreover, in the said description, although the single cell of the form with which a flow path is provided in a separator was illustrated, the separator of the form with which a flow path is not provided may be provided. In this case, for example, hydrogen or air can be supplied to the diffusion layer made of foam metal, sintered metal, or the like, and when the anode and / or the cathode is not provided with the diffusion layer, the anode catalyst It is also possible to adopt a form in which hydrogen, air, or the like is supplied to the layer and / or the cathode catalyst layer.

  Furthermore, in the description of the present invention, a single cell having a form in which a separator is provided is illustrated, but the single cell provided in the fuel cell system of the present invention is not limited to this form. For example, a cylindrical electrolyte membrane, a cylindrical anode catalyst layer disposed on the inner peripheral surface side of the electrolyte membrane, and a cylindrical cathode catalyst layer disposed on the outer peripheral surface side of the electrolyte membrane, A cylindrical single cell having a cylindrical MEA provided and current collectors respectively disposed on the outer peripheral surface side and the inner peripheral surface side of the cylindrical MEA may be provided. Even if such a single cell is provided, the effect obtained in the case of the above-described embodiment having a separator is provided if a liquid containing decomposition ions or a freeze inhibitor is supplied after the pressure of the single cell is reduced. It is possible to achieve the same effect as.

  Although the present invention applied to PEFC has been described so far, the fuel cell to which the present invention can be applied is not limited to PEFC. The present invention can be applied to a fuel cell capable of reducing the pressure in the closed space by the reaction of the substance that has passed through the solid polymer membrane in the closed space formed after the FC module is stopped. it can. Examples of the fuel cell include DMFC in addition to the PEFC. Therefore, the present invention is also applicable to DMFC.

It is the schematic which shows the fuel cell system of this invention concerning 1st Embodiment. It is sectional drawing which shows the example of a partial form of a single cell roughly. It is the schematic which shows the example of a form of a liquid supply means. It is a flowchart which shows the operation | movement procedure of a fuel cell system. It is a flowchart which shows the operation | movement procedure of a liquid supply means roughly. It is the schematic which shows the fuel cell system of this invention concerning 2nd Embodiment. It is a flowchart which shows the operation | movement procedure of a fuel cell system.

Explanation of symbols

1 Electrolyte membrane (electrolyte layer)
2 Anode (electrode layer)
2a Anode catalyst layer 2b Anode diffusion layer 3 Cathode (electrode layer)
3a Cathode catalyst layer 3b Cathode diffusion layer 4 MEA (electrolyte / electrode structure)
5, 6 Separator (current collector)
7, 8 Flow path 9 Single cell 10 Fuel cell module 20 Liquid supply means 21 Return liquid tank 22 Adjustment liquid tank 23 Ion detection means 24 Liquid feed pump 25 Electrodialysis cell 26 High concentration solution tank 27 Liquid feed line 28 Ion removal means 31 , 32, 33, 34 Valve 35, 36, 37, 38 Valve 41 First intake line 42 First exhaust line 43 Hydrogen supply line 44 Hydrogen recovery line 45 Liquid supply line 46 Liquid recovery line 47 Second intake line 48 Second exhaust line 50 Pressure reducing pump 51 Valve 52 Pressure reducing line 100, 200 Fuel cell system

Claims (3)

Electrolyte / electrode structure comprising an electrolyte layer, an electrode layer disposed on one side of the electrolyte layer, and an electrode layer disposed on the other side, and disposed on one side of the electrolyte / electrode structure And a current collector disposed on the other side, and a flow path through which a fluid supplied to the electrolyte / electrode structure can flow, and a module having a single cell,
The fuel cell system, wherein the liquid is supplied to the flow path where the pressure is reduced when the operation of the module is stopped. The fuel cell system according to claim 1, wherein the liquid contains ions having hydrogen peroxide decomposition performance. 3. The fuel cell system according to claim 2, wherein the ions having hydrogen peroxide decomposition performance are Ce ions.

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