JP2008282611A - Fuel cell system and fuel cell system operating method - Google Patents

Abstract

The present invention provides a fuel cell system and a fuel cell system operation method that suppress deterioration of a catalyst layer and fuel cell fuel consumption.
A fuel cell having an anode electrode and a cathode electrode, temperature detection means for detecting the temperature of the fuel cell, and when the temperature of the fuel cell detected by the temperature detection means is higher than a threshold temperature, Control means for controlling the potential of the cathode so that the potential of the cathode of the fuel cell is lower than the open circuit potential.
[Selection] Figure 3

Description

  The present invention relates to a fuel cell system and a technique for operating the fuel cell system.

  Generally, a fuel cell has a membrane-electrode assembly including a pair of electrodes (anode electrode and cathode electrode) sandwiching both sides of an electrolyte membrane, and a pair of fuel cell separators sandwiching both sides of the membrane-electrode assembly. . The anode electrode has an anode electrode catalyst layer and a diffusion layer, and the cathode electrode has a cathode electrode catalyst layer and a diffusion layer. At the time of power generation of the fuel cell, when the anode gas supplied to the anode electrode is hydrogen gas and the cathode gas supplied to the cathode electrode is oxygen gas, a reaction is performed on the anode electrode side to make hydrogen ions and electrons. The electrons reach the cathode electrode through an external circuit through the electrolyte membrane to the cathode electrode side. On the other hand, on the cathode side, hydrogen ions, electrons, and oxygen gas react to generate moisture, and energy is released.

  When a fuel cell is used as a power source for automobiles, load fluctuations such as acceleration and deceleration of the vehicle are frequently executed. Thereby, the potential of the cathode electrode of the fuel cell rises to an open circuit potential (or a potential close thereto), and the cathode electrode catalyst layer may be deteriorated. Further, even when the fuel cell stops generating power, the potential of the cathode electrode rises to an open circuit potential or a potential close thereto, and the cathode electrode catalyst layer may deteriorate.

  The deterioration of the cathode electrode catalyst layer includes elution of the catalyst metal used in the catalyst layer, reduction of the reaction area of the catalyst metal due to sintering, and the like.

  For example, a fuel cell system that prevents the cathode electrode potential from rising to an open circuit potential due to load fluctuations such as acceleration / deceleration of a vehicle and prevents deterioration of the cathode electrode catalyst layer has been proposed (for example, Patent Documents). 1 and 2).

  In addition, for example, a fuel cell system has been proposed in which the cathode electrode potential is prevented from rising to an open circuit potential when power generation of the fuel cell is stopped, and deterioration of the cathode electrode catalyst layer is prevented (for example, Patent Documents 3 and 4). reference).

  The deterioration of the cathode electrode catalyst layer is easily affected by temperature. That is, when the temperature of the fuel cell increases due to the power generation of the fuel cell and the potential of the cathode electrode rises to the open circuit potential, the cathode electrode catalyst layer deteriorates. However, when the temperature of the fuel cell is low, the cathode catalyst layer is unlikely to deteriorate even if the potential of the cathode electrode rises to the open circuit potential. Further, in order to avoid the cathode electrode potential from rising to the open circuit potential, it is necessary to generate power from the fuel cell. Therefore, the cathode electrode potential of the fuel cell is opened at low temperatures when the cathode catalyst layer is unlikely to deteriorate. If it is attempted to avoid the rise to the circuit potential, the fuel consumption of the fuel cell may deteriorate.

JP 2007-18781 A JP 2006-179242 A JP 2005-302304 A JP 2004-172105 A

  The present invention relates to a fuel cell system and a fuel cell system operation method that suppress deterioration of a catalyst layer and fuel cell fuel consumption.

  The present invention provides a fuel cell having an anode electrode and a cathode electrode, temperature detection means for detecting the temperature of the fuel cell, and when the temperature of the fuel cell detected by the temperature detection means is higher than a threshold temperature, Control means for controlling the cathode electrode potential so that the cathode potential of the fuel cell is lower than the open circuit potential.

  The present invention also provides a temperature detection step for detecting the temperature of a fuel cell having an anode electrode and a cathode electrode, and when the temperature of the fuel cell detected by the temperature detection step is higher than a threshold temperature, And a control step of controlling the cathode electrode potential so that the cathode electrode potential is lower than the open circuit potential.

  In the fuel cell system according to the present invention, a fuel cell having an anode electrode and a cathode electrode, a temperature detection unit for detecting the temperature of the fuel cell, and a temperature of the fuel cell detected by the temperature detection unit are higher than a threshold temperature. By providing the control means for controlling the cathode electrode potential so that the cathode potential of the fuel cell is lower than the open circuit potential, deterioration of the catalyst layer and fuel cell fuel consumption can be suppressed.

  In the operating method of the fuel cell system according to the present invention, the temperature detection step for detecting the temperature of the fuel cell having the anode electrode and the cathode electrode, and the temperature of the fuel cell detected by the temperature detection step is higher than the threshold temperature Further, by including a control step of controlling the cathode electrode potential so that the cathode potential of the fuel cell becomes lower than the open circuit potential, it is possible to suppress the deterioration of the catalyst layer and the fuel cell fuel consumption.

  Embodiments of the present invention will be described below.

  FIG. 1 is a schematic diagram showing an example of the configuration of a fuel cell system according to an embodiment of the present invention. As shown in FIG. 1, the fuel cell system 1 includes a fuel cell 10, a temperature sensor 12, a control device 14, a load device 16, an internal load 18, a distributor 19, an anode gas supply system, and a cathode gas supply system. It is what has.

  FIG. 2 is a schematic cross-sectional view showing an example of the configuration of the fuel cell used in the present invention. As shown in FIG. 2, the fuel cell 10 includes a membrane-electrode assembly 26 in which both sides of an electrolyte membrane 20 are sandwiched between an anode electrode 22 and a cathode electrode 24, and a fuel cell separator that sandwiches both outer sides of the membrane-electrode assembly 26. 28. Further, the fuel cell according to the present embodiment may be formed by stacking a plurality of fuel cells 10 as unit cells. The anode electrode 22 has an anode electrode catalyst layer 30 a and a diffusion layer 32, and the cathode electrode 24 has a cathode electrode catalyst layer 30 b and a diffusion layer 32.

  The anode electrode catalyst layer 30a and the cathode electrode catalyst layer 30b are formed on the diffusion layer 32 or the electrolyte membrane 20 by mixing, for example, carbon carrying a metal catalyst such as platinum or ruthenium and a perfluorosulfonic acid electrolyte. It is formed by filming. The diffusion layer 32 is made of a porous material such as carbon cloth. The electrolyte membrane 20 is a membrane having proton conductivity, and for example, a perfluorosulfonic acid resin membrane or the like is used. The fuel cell separator 28 supplies a reaction gas to the anode electrode 22 or the cathode electrode 24 through the reaction gas channel 34, and a metal plate, a carbon plate, or the like is used.

  The anode gas supply system includes an anode gas cylinder 36, a valve 38, and an anode gas supply pipe 40 as shown in FIG. The anode gas supply pipe 40 connects the anode gas cylinder 36 and the fuel cell 10. The anode gas is hydrogen gas or the like. The cathode gas supply system includes a compressor 42, a valve 44, and a cathode gas supply pipe 46 as shown in FIG. The cathode gas supply pipe 46 connects the compressor 42 and the fuel cell 10. The cathode gas is air or the like.

  The load device 16 uses the fuel cell 10 as a power source, and is electrically connected to the fuel cell 10 via a distributor 19. Examples of the load device 16 include an electric motor. The internal load 18 consumes surplus power of the fuel cell 10 and is electrically connected to the fuel cell 10 via the distributor 19. An example of the internal load 18 is a secondary battery.

  The temperature sensor 12 detects the temperature of the fuel cell 10 and sends temperature data to the control device 14, and is electrically connected to the control device 14. The temperature of the fuel cell 10 may be the temperature of the fuel cell 10 itself, or the cooling water supplied to the fuel cell 10 (formed on the side opposite to the reaction gas flow path 34 of the fuel cell separator 28 shown in FIG. 2). Or the temperature of a cooling water flow path (not shown).

  The control device 14 is a microcomputer or the like that stores a predetermined threshold temperature in a memory. Although details of the operation of the control device 14 will be described later, when the temperature of the fuel cell 10 is higher than the threshold temperature by comparing the temperature of the fuel cell 10 detected by the temperature sensor 12 with a preset threshold temperature, the fuel The cathode electrode potential is controlled so that the cathode electrode potential of the battery 10 is lower than the open circuit potential (high potential avoiding process), and when the temperature is equal to or lower than the threshold temperature, the cathode electrode potential is not controlled. When the temperature is equal to or lower than the threshold temperature recorded in the control device 14, even if the cathode electrode potential reaches the open circuit potential, the cathode electrode catalyst layer 30b hardly deteriorates. The threshold temperature is appropriately set depending on the size of the electrode, the specification of the electrode, the material used for the electrode, and the like. For example, the threshold temperature is preferably set to 80 ° C. The control device 14 controls the distributor 19 to determine the amount of power distribution (supply) to the load device 16 and the internal load 18.

  The open circuit potential of the cathode electrode 24 is theoretically 1.23 V (vs. SHE). Near V (vs. SHE). In addition, the open circuit potential may rise from 1.23 V due to the stoppage of power generation of the fuel cell. That is, the open circuit potential in the present embodiment is in the range of about 1.0 V or more. When the temperature of the fuel cell 10 is higher than the threshold temperature, the cathode electrode catalyst layer 30b is likely to deteriorate when the cathode electrode potential reaches the open circuit potential due to power generation stop of the fuel cell 10, load fluctuation, etc. When the temperature of 10 is lower than the threshold temperature, even if the open circuit potential is reached, the cathode catalyst layer 30b is unlikely to deteriorate. Therefore, in this embodiment, when the temperature of the fuel cell 10 is higher than the threshold temperature, the control device 14 controls the cathode electrode potential to be lower than the open circuit potential, and the temperature of the fuel cell 10 is equal to or lower than the threshold temperature. In this case, the cathode potential is not controlled.

  A method for operating the fuel cell system will be described.

  In the power generation of the fuel cell 10 shown in FIG. 1, the anode gas is supplied from the anode gas cylinder 36 by opening the valve 38 of the anode gas supply pipe 40 on the anode electrode side. Then, the anode gas is supplied to the fuel cell 10 through the anode gas supply pipe 40 and used for power generation. The anode gas not used for power generation is discharged out of the fuel cell 10 from the anode gas discharge pipe 48 as an anode off gas. On the other hand, on the cathode electrode side, the valve 44 of the cathode gas supply pipe 46 is opened, and the cathode gas is supplied from the compressor 42. The cathode gas is supplied to the fuel cell 10 through the cathode gas supply pipe 46 and used for power generation. The cathode gas not used for power generation is discharged out of the fuel cell 10 from the cathode gas discharge pipe 50 as a cathode off gas. The electric power generated by the power generation of the fuel cell 10 is consumed by the load device 16 via the distributor 19.

FIG. 3 is a flowchart showing an example of an operation method of the fuel cell system when the fuel cell is stopped. When power generation of the fuel cell is stopped, as shown in FIG. 3, first, in step S10, the temperature (T ₁ ) of the fuel cell 10 is detected by the temperature sensor 12. The control device 14 compares the threshold temperature (T ₀ ) with the temperature (T ₁ ) of the fuel cell 10 detected by the temperature sensor 12, and when the temperature of the fuel cell 10 detected by the temperature sensor 12 is higher than the threshold temperature. In step S12, high potential avoidance processing for the cathode electrode 24 is performed, and in step S14, power generation of the fuel cell 10 is stopped. On the other hand, when the detected temperature of the fuel cell 10 is equal to or lower than the threshold temperature, the high potential avoidance process of the cathode electrode 24 is not performed, and the power generation of the fuel cell 10 is stopped (step S14).

  The high potential avoidance process of the cathode electrode when the fuel cell is stopped is a process of controlling the cathode electrode potential so that the cathode electrode potential becomes lower than the open circuit potential as described above. Specifically, according to an instruction from the control device 14, the valve 44 of the cathode gas supply pipe 46 is closed, and the supply of the cathode gas to the fuel cell 10 is stopped. At this time, the supply of the anode gas to the fuel cell 10 is continued without being stopped. As a result, the cathode gas remaining in the fuel cell 10 is generated by the power generation of the fuel cell 10 and the voltage of the fuel cell 10 is lowered. Therefore, it is possible to avoid the cathode electrode 24 from rising to the open circuit potential. Further, the electric power of the fuel cell 10 generated by the reaction of the remaining cathode gas and anode gas is consumed by the internal load 18 via the distributor 19.

  Thereafter, the valve 38 of the anode gas supply pipe 40 is closed by an instruction from the control device 14, and the supply of the anode gas to the fuel cell 10 is stopped. The anode gas supply time may be set in advance in the memory of the control device 14, or a voltage sensor is provided in the control device 14 so that the voltage of the fuel cell 10 becomes a predetermined level or less. The supply of anode gas may be stopped.

  As described above, in the present embodiment, when the temperature of the fuel cell detected by the temperature sensor is higher than the threshold temperature set by the control unit, the high potential avoidance process is performed. Deterioration can be suppressed. In addition, when the temperature of the fuel cell detected by the temperature sensor is lower than the threshold temperature set by the control unit, the fuel cell is stopped without performing the high potential avoidance process, so that the consumption of anode gas is suppressed. Can improve fuel efficiency. When the temperature is lower than the threshold temperature, the cathode electrode catalyst layer is unlikely to deteriorate even if the high potential avoidance process is not performed.

  FIG. 4 is a flowchart showing an example of a method of operating the fuel cell system when the load fluctuates. When load fluctuation occurs, surplus power is generated in the fuel cell, so that the voltage of the fuel cell rises and the cathode potential rises. Also in such a case, as shown in FIG. 4, the temperature of the fuel cell 10 is detected by the temperature sensor 12 in step S20. The control device 14 compares the threshold temperature with the temperature of the fuel cell 10 detected by the temperature sensor 12. If the temperature of the fuel cell 10 detected by the temperature sensor 12 is higher than the threshold temperature, in step S22, the cathode electrode In step S24, the power generation of the fuel cell 10 is continued. On the other hand, when the detected temperature is equal to or lower than the threshold temperature, the high potential avoidance process for the cathode electrode 24 is not performed, and the power generation of the fuel cell 10 is continued (step S24).

  In the high potential avoidance process due to potential fluctuation during power generation, the control device 14 controls the distributor 19 to distribute the electric power during normal power generation of the fuel cell 10 to the internal load 18 to be consumed (charged). Then, after the internal load 18 reaches full charge, power generation of the fuel cell 10 is stopped. As a result, the voltage of the fuel cell 10 decreases, and the cathode potential can be prevented from rising to the open circuit potential.

  Similarly to the above, in this embodiment, when the temperature of the fuel cell detected by the temperature sensor is higher than the threshold temperature set by the control unit, the high potential avoidance process is performed. Deterioration can be suppressed. Further, when the temperature is lower than the threshold temperature, power generation can be continued without performing high potential avoidance processing, and excessive gas consumption and excessive auxiliary machine loss can be suppressed, so that fuel efficiency of the fuel cell can be improved. .

  The fuel cell system according to the present embodiment can be used as, for example, an automobile power source, a household power source, or the like.

It is a schematic diagram which shows an example of a structure of the fuel cell system which concerns on embodiment of this invention. It is a schematic cross section which shows an example of a structure of the fuel cell used for this invention. It is a flowchart which shows an example of the operating method of a fuel cell system at the time of a stop of a fuel cell. It is a flowchart which shows an example of the operating method of the fuel cell system at the time of load fluctuation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell system, 10 Fuel cell, 12 Temperature sensor, 14 Control apparatus, 16 Load apparatus, 18 Internal load, 19 Distributor, 20 Electrolyte membrane, 22 Anode electrode, 24 Cathode electrode, 26 Membrane-electrode assembly, 28 Fuel cell Separator, 30a anode electrode catalyst layer, 30b cathode electrode catalyst layer, 32 diffusion layer, 34 reaction gas flow path, 36 anode gas cylinder, 38 valve, 40 anode gas supply pipe, 42 compressor,
44 valve, 46 cathode gas supply pipe, 48 anode gas discharge pipe, 50 cathode gas discharge pipe.

Claims (2)

A fuel cell having an anode and a cathode;
Temperature detecting means for detecting the temperature of the fuel cell;
A control device for controlling the potential of the cathode electrode so that the potential of the cathode electrode of the fuel cell is lower than an open circuit potential when the temperature of the fuel cell detected by the temperature detection means is higher than a threshold temperature;
A fuel cell system comprising: A temperature detecting step for detecting the temperature of a fuel cell having an anode and a cathode; and
A control step of controlling the cathode electrode potential so that the cathode potential of the fuel cell is lower than an open circuit potential when the temperature of the fuel cell detected by the temperature detection step is higher than a threshold temperature;
A method for operating a fuel cell system, comprising:

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