JP7211129B2 - FUEL CELL SYSTEM AND METHOD OF OPERATION OF FUEL CELL - Google Patents

Description

The present disclosure relates to fuel cell systems and methods of operating fuel cells.

Patent Literature 1 discloses a fuel cell system including an electrode catalyst layer comprising an electrode catalyst in which catalyst particles such as platinum are supported on a carbon particle carrier. In such an electrode catalyst, a deterioration phenomenon in which platinum particles are eluted or coarsened by load fluctuations is accelerated, and under high humidity, the elution or coarsening of platinum particles is further promoted by load fluctuations. On the other hand, under low humidification, power generation characteristics are reduced, but elution or coarsening of platinum particles due to load fluctuations is suppressed. Therefore, only when the voltage is temporarily high when starting and stopping or when the load changes immediately after idling of the fuel cell, the low humidification state is set to suppress the elution or coarsening of platinum particles due to high voltage and load changes. After the temperature is stabilized, a highly humidified state is set to improve power generation characteristics, and both deterioration of the electrodes and improvement of power generation characteristics are achieved.

Further, Patent Document 1 discloses a fuel cell system in which the cathode is changed from one in which catalyst particles such as platinum are supported on a carbon particle carrier to one in which catalyst particles such as platinum are supported on a tin oxide-based ceramic particle carrier. is disclosed.

JP 2017-117599 A

By the way, in the case of a cathode in which catalyst particles are supported on a ceramic particle carrier, if the inside of the fuel cell is kept at a low humidity in order to suppress the deterioration of the catalyst particles, the cell resistance increases and the output performance of the fuel cell is suppressed. The output performance of the fuel cell cannot be quickly recovered only by highly humidifying the inside of the.

In view of the circumstances described above, at least one embodiment of the present invention provides a fuel cell system and a fuel cell operation method capable of quickly recovering the output performance of a fuel cell whose output performance has been suppressed due to the suppression of deterioration of catalyst particles. intended to provide

(1) A fuel cell system according to at least one embodiment of the present invention includes a fuel cell using an electrode in which catalyst particles are supported on a ceramic particle carrier as at least the cathode of an anode and a cathode, and hydrogen is supplied to the anode. an air supply means capable of supplying air to the cathode and capable of adjusting the flow rate and pressure of the air supplied to the cathode; and a load connected to the fuel cell. a load adjusting means whose size is adjustable; a normal operation control means for controlling the hydrogen supply source and the air supply means so as to supply hydrogen and air while the inside of the fuel cell is humidified; The air is adjusted so that the humidity inside the battery is lower than the state controlled by the normal operation control means and the oxygen partial pressure of the air supplied to the cathode is higher than the state controlled by the normal operation control means. a deterioration suppressing operation control means for controlling the supply means; and a micro load applied to the fuel cell, and thereafter controlling the load adjustment means so that the cell voltage of the fuel cell becomes constant. an output performance recovery operation control means for controlling the air supply means so that the air supplied to the engine has a pressure equivalent to that controlled by the normal operation control means.

According to the above configuration (1), the deterioration suppression operation control means reduces the humidity inside the fuel cell below the state controlled by the normal operation control means, and the oxygen partial pressure of the air supplied to the cathode is reduced to normal operation. The air supply means is controlled to be higher than the state controlled by the control means. As a result, an electron depletion layer is formed on the surface of the ceramic particle carrier, thereby suppressing the output performance of the fuel cell and suppressing deterioration of the catalyst particles supported on the ceramic particle carrier. Further, the output performance recovery operation control means applies a minute load to the fuel cell, and thereafter controls the load adjustment means so that the cell voltage of the fuel cell becomes constant. The air supply means is controlled so that the pressure is the same as the conditions the means controls. As a result, the disappearance of the electron depletion layer formed on the surface of the ceramic particle carrier can be accelerated, so that the output performance of the fuel cell whose output performance has been suppressed due to the suppression of deterioration of the catalyst particles can be quickly recovered.

(2) In some embodiments, in the configuration of (1) above, the output performance recovery operation control means terminates control when the cell resistance value of the fuel cell converges within a predetermined range.

According to the configuration (2) above, the output performance recovery operation control means ends control when the value of the cell resistance of the fuel cell converges within a predetermined range, so that the fuel cell system can start normal operation. .

(3) In some embodiments, in the configuration (1) or (2) above, the deterioration suppression operation control means controls the load so that the load becomes smaller than the state controlled by the normal operation control means. Control the load adjustment means.

According to the above configuration (3), the deterioration suppressing operation control means controls the load adjustment means so that the load becomes smaller than the state controlled by the normal operation control means in a state in which the internal humidity is low and an electron depletion layer is formed. is controlled, it is possible to suppress the elution deterioration acceleration reaction of the oxidized platinum particles.

(4) A method of operating a fuel cell according to an embodiment of the present invention is a method of operating a fuel cell using an electrode in which catalyst particles are supported on a ceramic particle carrier as at least the cathode of the anode and the cathode, a normal operation step of supplying air and hydrogen while the interior of the fuel cell is humidified; A deterioration suppressing operation step in which an electron depletion layer is formed on the surface of the ceramic particle support by increasing the number of steps compared to the normal operation step, and a micro load is applied to the fuel cell so that the cell voltage of the fuel cell is constant. and an output performance recovery operation step of increasing the load to eliminate the electron depletion layer.

According to the above method (4), the output performance recovery operation step applies a minute load to the fuel cell and increases the load so that the cell voltage of the fuel cell becomes constant, thereby eliminating the electron depletion layer. , the output performance of the fuel cell, whose output performance has been suppressed due to the suppression of deterioration of the catalyst particles, can be quickly recovered.

(5) In some embodiments, in the method of (4) above, the output performance recovery operation step ends when the cell resistance value of the fuel cell converges within a predetermined range.

According to method (5) above, the output performance recovery operation control step ends when the cell resistance value of the fuel cell converges within the predetermined range, so the fuel cell can start normal operation.

According to at least one embodiment of the present invention, it is possible to quickly restore the output performance of a fuel cell whose output performance has been suppressed due to suppression of deterioration of catalyst particles.

1 is a block diagram schematically showing the configuration of a fuel cell vehicle equipped with a fuel cell system according to an embodiment of the present invention; FIG. 2 is a diagram schematically showing the configuration of the fuel cell shown in FIG. 1; FIG. 2 is a block diagram schematically showing the configuration of a control device shown in FIG. 1; FIG. FIG. 4 is a diagram for explaining the deterioration mechanism of an electrode in which catalyst particles are supported on a ceramic particle carrier; 2 is a timing chart showing operation timings of the fuel cell system shown in FIG. 1; FIG. 2 is a diagram schematically showing the configuration of an electrode in which catalyst particles are carried on a ceramic particle carrier; 3 is a flow chart schematically showing a method of operating a fuel cell according to an embodiment of the invention;

An embodiment of the present invention will be described below with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention, and are merely illustrative examples. Absent.

FIG. 1 is a block diagram schematically showing the configuration of a fuel cell vehicle 100 equipped with a fuel cell system 1 according to an embodiment of the invention. FIG. 2 is a diagram schematically showing the configuration of the fuel cell 2 shown in FIG. 1. As shown in FIG. FIG. 3 is a block diagram schematically showing the configuration of control device 10 shown in FIG.

As shown in FIG. 1, a fuel cell vehicle (FCV (Fuel Cell Vehicle)) 100 equipped with a fuel cell system 1 according to an embodiment of the present invention is a range extender type electric vehicle that uses a driving battery. When power is supplied from the (secondary battery) 6 to the motor 7 to charge the driving battery 6, or when the power supplied from the driving battery 6 to the motor 7 is insufficient (when the output of the motor 7 is insufficient) The fuel cell system 1 is operated.

A fuel cell vehicle 100 equipped with a fuel cell system 1 according to one embodiment of the present invention includes a fuel cell system 1, a DC/DC converter 8, a drive battery 6, an inverter 9, a motor 7, and a control device (FCV-ECU). ) 10.

The fuel cell system 1 includes a fuel cell (FC (Fuel Cell)) 2, a hydrogen supply source 3 and air supply means 4, and is controlled by a controller 10 together with a DC/DC converter 8, a drive battery 6, an inverter 9 and a motor 7. controlled. In this sense, the control device 10 forms part of the fuel cell system 1 .

The fuel cell 2 can generate electric power through an electrochemical reaction between a fuel gas (hydrogen) and an oxidizing gas (oxygen). The fuel cell 2 is configured by stacking a plurality of single cells (not shown).

As shown in FIG. 2, in the fuel cell 2 according to one embodiment of the present invention, of an anode (negative electrode) 21 and a cathode (positive electrode) 22, at least the cathode 22 carries catalyst particles 222 on a ceramic particle carrier 221. Use electrodes. The ceramics are, for example, tin oxide ceramics. The catalyst particles 222 are, for example, noble metal catalyst particles 222, for example, platinum nanoparticles.

A fuel gas (hydrogen gas) can be supplied to the anode 21 , and an oxidizing gas (air) can be supplied to the cathode 22 . As a result, at the anode 21, the fuel gas is decomposed into protons (hydrogen ions H ⁺ ) and electrons by the reaction H ₂ →2H ⁺ +2e ⁻ , the protons move through the electrolyte membrane 23 to the cathode 22, and the electrons through the interior to the cathode 22 . On the other hand, at the cathode 22, protons and electrons react with oxygen contained in the oxidizing gas, and the reaction of 4H ⁺ +O ₂ +4e ⁻ →2H ₂ O produces water (hereinafter referred to as “reaction water”). Thereby, the inside of the fuel cell 2 is humidified.

As shown in FIG. 1, the fuel cell 2 is provided with a thermometer (temperature sensor) 24 . The temperature sensor 24 is connected to the control device 10 and the operating temperature of the fuel cell 2 is managed by the control device 10 .

The fuel cell 2 is also provided with a fuel cell resistance meter 25 . The fuel cell resistance meter 25 is connected to the control device 10 and the cell resistance of the fuel cell 2 is managed by the control device 10 .

The hydrogen supply source 3 is a supply source capable of supplying hydrogen (fuel gas) to the anode 21 and includes, for example, a hydrogen tank ₍ H2 tank) 31 , a main valve 32 and a pressure reducing valve 33 . Therefore, the hydrogen supply source 3 can arbitrarily select supply/stop of hydrogen to be supplied to the anode 21 and can arbitrarily adjust the pressure of hydrogen to be supplied to the anode 21 .

The air supply means 4 is a supply means capable of supplying air (oxidizing gas) to the cathode 22 . The air supplied to the cathode 22 by the air supply means 4 is, for example, non-humidified air introduced from the atmosphere. As a result, the inside of the fuel cell 2 can be kept at low humidity immediately after the power generation of the fuel cell 2 is started. deterioration of the catalyst particles 222 supported on the particle carrier 221 can be suppressed.

The air supply means 4 is composed of, for example, a naturally aspirated air by running the fuel cell vehicle 100 and an air compressor 41 . Therefore, air can be supplied to the cathode 22 by running the fuel cell vehicle 100 , and air can be supplied to the cathode 22 by operating the air compressor 41 .

The air supply means 4 can adjust the flow rate of air supplied to the cathode 22 . The flow rate of the air supplied to the cathode 22 can be adjusted by the running speed of the fuel cell vehicle 100, for example. Moreover, the flow rate of the air supplied to the cathode 22 can also be adjusted by operating the air compressor 41, for example.

The air supply means 4 is provided with a flow meter (flow sensor) 42 . The flow rate sensor 42 is connected to the control device 10 so that the flow rate of the air supplied to the cathode 22 can be managed by the control device 10 .

The fuel cell system 1 according to one embodiment of the invention further comprises hydrogen recirculation means 5 . The hydrogen recirculation means 5 is means for recirculating the hydrogen discharged from the fuel cell 2 to the anode 21 and includes, for example, a hydrogen recirculation pump 51 .

FIG. 4 is a diagram for explaining the deterioration suppression mechanism of an electrode in which a catalyst 222 is supported on a ceramic carrier 221. FIG. Here, the deterioration suppression mechanism of an electrode in which platinum (Pt) is supported on a ceramic carrier will be described as an example.

The electrochemical oxidation reaction of Pt (Pt→Pt ²⁺ +2e ⁻ ) is a reaction accompanied by electron transfer. In the case of the ceramic carrier 221 (for example, tin oxide), electrons on the surface of the carrier are taken away by adsorbing oxygen on the ceramic carrier 221 . As a result, as shown in FIG. 4A, the electron concentration on the surface of the ceramic carrier 221 (SnO ₂ ) is reduced, and an electron depletion layer 223 is formed on the surface of the ceramic carrier 221 in which electrons are less likely to move. (By this, the electron depletion layer 223 can be called a deterioration suppression layer). Since the electron depletion layer 223 makes it difficult for electrons to move in the Pt deterioration acceleration reaction, the deterioration of Pt is suppressed. As a result, the output of the fuel cell 2 is suppressed.

Therefore, in order to restore the output of the fuel cell 2, it is necessary to eliminate the electron depletion layer 223 formed on the surface of the ceramic carrier 221 (SnO ₂ ). When the electron depletion layer 223 formed on the surface of the ceramic carrier 221 (SnO ₂ ) disappears, the movement of electrons becomes easier and the output of the fuel cell 2 recovers.

In the fuel cell system 1 according to one embodiment of the present invention, deterioration of the fuel cell 2 is suppressed and high output operation of the fuel cell 2 is suppressed by executing normal operation, deterioration suppression operation, and output performance recovery operation in this order. to enable.

The fuel cell system 1 according to one embodiment of the present invention further includes a load adjustment means 11, a normal operation control means 12, and a deterioration suppression operation to enable the above-described normal operation, deterioration suppression operation, and output performance recovery operation. A control means 13 and an output performance recovery operation control means 14 are provided.

The load adjusting means 11 can adjust the magnitude of the load connected to the fuel cell 2 . The load is, for example, the DC/DC converter 8, the inverter 9, the drive battery 6, or the motor 7, and the load adjustment means 11 can arbitrarily adjust the magnitude of these loads. The load adjustment means 11 is provided, for example, in a controller 10 that controls the DC/DC converter 8, the inverter 9, and the motor 7 (see FIG. 3).

The normal operation control means 12 controls the hydrogen supply source 3 and the air supply means 4 so as to supply hydrogen and air while the inside of the fuel cell 2 is humidified. As a result, hydrogen and air are supplied while the interior of the fuel cell 2 is humidified (normal operation). In normal operation, as shown in FIG. 6A, electrons flow from the catalyst 222 to the ceramic carrier 221, enabling the fuel cell 2 to operate at high output.

The normal operation control means 12 is provided, for example, in the control device 10 that controls the hydrogen supply source 3 (main valve 32, pressure reducing valve 33) and the air supply means 4 (air compressor 41) (see FIG. 3).

The deterioration suppression operation control means 13 controls the oxygen partial pressure of the air supplied to the cathode 22 when the humidity inside the fuel cell 2 is lower than the state controlled by the normal operation control means 12. The air supply means 4 is controlled so as to be higher than the state. As a result, as shown in FIG. 5, the humidity inside the fuel cell 2 (the degree of humidification of the air electrode 22) decreases, and the oxygen partial pressure of the air supplied to the cathode 22 increases (deterioration suppression operation). In the deterioration suppression operation, the oxygen partial pressure of the air supplied to the cathode 22 increases, so the electron concentration on the surface of the ceramic carrier 221 (SnO ₂ ) decreases, and as shown in FIG. An electron depletion layer 223 is formed on the surface of the carrier 221 . This makes it difficult for electrons to flow from the catalyst 222 to the ceramic carrier 221 , thereby suppressing deterioration of the fuel cell 2 . In order to increase the oxygen partial pressure, the air compressor 41 may be operated, or the air exhaust port of the fuel cell 2 may be closed (dead-end system).

The deterioration suppression operation control means 13 is provided, for example, in the control device 10 that controls the air supply means 4 (air compressor 41) (see FIG. 3).

Further, the deterioration suppressing operation control means 13 controls the load adjustment means 11 so that the load of the fuel cell 2 becomes smaller than the state controlled by the normal operation control means 12 in a state in which the internal humidity is low and an electron depletion layer is formed. control (eg control to no load). As a result, the fuel cell 2 becomes unloaded, and the elution deterioration acceleration reaction of the oxidized catalyst particles 222 (for example, platinum particles) can be suppressed.

The output performance recovery operation control means 14 applies a minute load to the fuel cell 2 and then controls the load adjustment means 11 so that the cell voltage of the fuel cell 2 becomes constant. The air supply means 4 is controlled so that the pressure is the same as the state controlled by the normal operation control means 12 . As a result, as shown in FIG. 5, when a minute load is applied to the fuel cell 2, the cell voltage of the fuel cell 2 drops once. When the load adjustment means 11 is controlled so that the cell voltage of the fuel cell 2 is constant, the load connected to the fuel cell 2 is adjusted to gradually increase, and the humidity inside the fuel cell 2 (the air electrode 22 humidification) gradually increases. In addition, the air supplied to the cathode 22 has a pressure equivalent to the state controlled by the normal operation control means 12 (output performance recovery operation).

In the output performance recovery operation, the cell voltage of the fuel cell 2 drops once and the load connected to the fuel cell 2 gradually increases, so that the thickness of the electron depletion layer 223 gradually decreases as shown in FIG. 6(c). , the electron depletion layer 223 eventually disappears.

Further, the output performance recovery operation control means 14 ends the control when the cell resistance value of the fuel cell 2 converges within a predetermined range. The predetermined range is, for example, XΩ to YΩ, and the control is terminated when converging within a range recognized as constant. As a result, the fuel cell system 1 can start (restart) normal operation (see FIG. 6(d)).

According to the fuel cell system 1 according to the embodiment of the present invention described above, the deterioration suppressing operation control means 13 causes the humidity inside the fuel cell 2 to fall below the state controlled by the normal operation control means 12, and the cathode 22 The air supply means 4 is controlled so that the oxygen partial pressure of the air supplied to is higher than the state controlled by the normal operation control means 12 . As a result, an electron depletion layer 223 is formed on the surface of the ceramic particle carrier 221, so that the output performance of the fuel cell 2 is suppressed, and the elution deterioration acceleration reaction of the oxidized catalyst particles 222 (platinum particles) is suppressed. can be done. Further, the output performance recovery operation control means 14 applies a minute load to the fuel cell 2, and thereafter controls the load adjustment means 11 so that the cell voltage of the fuel cell 2 becomes constant, and supplies the voltage to the cathode 22. The air supply means 4 is controlled so that the air has the same pressure as the state controlled by the normal operation control means 12 . As a result, the disappearance of the electron depletion layer 223 formed on the surface of the ceramic particle support 221 can be accelerated. can recover to

FIG. 7 is a flow chart schematically showing a method of operating the fuel cell 2 according to one embodiment of the invention.

The method of operating the fuel cell 2 according to one embodiment of the present invention is a method of operating the fuel cell 2 in which, of the anode 21 and the cathode 22, at least the cathode 22 uses an electrode in which catalyst particles 222 are supported on a ceramic particle carrier 221. be.

The method of operating a fuel cell according to this embodiment includes a normal operation step (step S1), a deterioration suppression operation step (step S3), and an output performance recovery operation step (step S5).

The normal operation step (step S1) is a step of supplying air and hydrogen while the inside of the fuel cell 2 is humidified. When the normal operation process ends (step S2: Yes), the process proceeds to the deterioration suppression operation process (step S3).

In the deterioration suppression operation step (step S3), the humidity inside the fuel cell 2 is reduced to a level lower than that in the normal operation step (step S1), and the oxygen partial pressure of the air supplied to the fuel cell 2 is reduced to that of the normal operation step (step S1). , to form an electron depletion layer 223 on the surface of the ceramic particle carrier 221 . When the deterioration suppression operation process ends (step S4: Yes), the process proceeds to the output performance recovery operation process (step S5).

The output performance recovery operation step (step S5) is a step in which a minute load is applied to the fuel cell 2, and then the load is increased so that the cell voltage of the fuel cell 2 becomes constant, and the electron depletion layer 223 disappears. .

Moreover, the output performance recovery step (step S5) ends when the value of the cell resistance of the fuel cell 2 converges within a predetermined range (step S6: Yes). The predetermined range is, for example, XΩ to YΩ, and ends when it converges within a range recognized as constant. As a result, the fuel cell can resume the normal operation process (step S1).

According to the method of operating the fuel cell 2 according to the embodiment of the present invention described above, the output performance recovery operation step (step S3) applies a minute load to the fuel cell 2 and keeps the cell voltage of the fuel cell 2 constant. Since the load can be increased to accelerate the disappearance of the electron depletion layer 223, the output performance of the fuel cell whose output performance has been suppressed due to the suppression of deterioration of the catalyst particles can be quickly restored.

The present invention is not limited to the above-described embodiments, and includes modifications of the above-described embodiments and modes in which these modes are combined as appropriate.

1 fuel cell system 2 fuel cell 21 anode 22 cathode (air electrode)
221 Particle Carriers (Carriers)
222 catalyst particles (catalyst)
223 electron depletion layer 23 electrolyte membrane 24 thermometer (temperature sensor)
25 fuel cell resistance meter 3 hydrogen supply source 31 hydrogen tank 32 main valve 33 pressure reducing valve 4 air supply means 41 air compressor 42 flow meter (flow sensor)
5 Hydrogen Recirculation Means 51 Hydrogen Recirculation Pump 6 Driving Battery 7 Motor 8 DC/DC Converter 9 Inverter 10 Control Device (FCV, ECU)
REFERENCE SIGNS LIST 11 load adjustment means 12 normal operation control means 13 deterioration suppression operation control means 14 output performance recovery operation control means 100 fuel cell vehicle

Claims (5)

A fuel cell using an electrode in which catalyst particles are supported on a ceramic particle carrier, at least for the cathode of the anode and the cathode;
a hydrogen supply source capable of supplying hydrogen to the anode;
air supply means capable of supplying air to the cathode and capable of adjusting the flow rate and pressure of the air supplied to the cathode;
load adjusting means capable of adjusting the magnitude of the load connected to the fuel cell;
normal operation control means for controlling the hydrogen supply source and the air supply means so as to supply hydrogen and air while the inside of the fuel cell is humidified;
so that the humidity inside the fuel cell is lower than the state controlled by the normal operation control means, and the oxygen partial pressure of the air supplied to the cathode is higher than the state controlled by the normal operation control means; deterioration suppression operation control means for controlling the air supply means;
A state in which a minute load is applied to the fuel cell, and then the load adjustment means is controlled so that the cell voltage of the fuel cell becomes constant, and the air supplied to the cathode is controlled by the normal operation control means. and an output performance recovery operation control means for controlling the air supply means so that the pressure becomes equal to the pressure of the fuel cell system. 2. The fuel cell system according to claim 1, wherein said output performance recovery operation control means terminates control when a value of cell resistance of said fuel cell converges within a predetermined range. 3. The fuel cell system according to claim 1, wherein the deterioration suppression operation control means controls the load adjustment means so that the load becomes smaller than the state controlled by the normal operation control means. . A method of operating a fuel cell using an electrode in which catalyst particles are supported on a ceramic particle carrier as at least the cathode of the anode and the cathode,
a normal operation step of supplying air and hydrogen while the interior of the fuel cell is humidified;
The humidity inside the fuel cell is lowered below that in the normal operation process, the oxygen partial pressure of the air supplied to the fuel cell is increased above that in the normal operation process, and an electron depleted layer is formed on the surface of the ceramic particle carrier. A deterioration suppression operation step that forms
an output performance recovery operation step of applying a minute load to the fuel cell and increasing the load so that the cell voltage of the fuel cell becomes constant to eliminate the electron depletion layer;
A method of operating a fuel cell, comprising: 5. The method of operating a fuel cell according to claim 4, wherein the output performance recovery operation step ends when the cell resistance of the fuel cell converges within a predetermined range.

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