KR20150015635A - Recovery method of coolant leak in polymer electrolyte membrane fuel cell - Google Patents

Abstract

The present invention relates to a method for restoring the capacity of fuel cells when antifreeze liquid and coolant are leaked in polymer electrolyte fuel cells, the method comprising steps of restoring the capacity of poisoned catalyst by injecting water into an entrance on an anode electrode and a cathode electrode of the fuel cell or by injecting air into an anode electrode and hydrogen into a cathode electrode, thereby restoring the capacity of the fuel cell, when antifreeze liquid and coolant are leaked in polymer electrolyte fuel cells, without decomposing stack and unit cells.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for recovering performance of a fuel cell when an antifreeze and a cooling water are leaked from a polymer electrolyte fuel cell,

The present invention relates to a new method for recovering the performance of a fuel cell without disassembling a stack and a unit cell in an antifreeze or cooling water leakage in a polymer electrolyte fuel cell.

A polymer electrolyte fuel cell (FEP) is a fuel cell that uses a polymer membrane with hydrogen ion-exchange properties as an electrolyte. The polymer electrolyte fuel cell (SPFC), polymer electrolyte fuel cell (PEFC) fuel cell (PEMFC). Polymer electrolyte fuel cells with lower operating temperatures than other types of fuel cells have high efficiency, high current density and power density, short startup times and fast response to load changes (LJMJ Blomen and MN Mugerwa, " Fuel Cell Systems ", Plenum Press, New York, 1993). Especially, since the polymer membrane is used as the electrolyte, there is no electrolyte loss, and it is possible to apply the methanol reformer, which is an established technology, and is less sensitive to the change of the reaction gas pressure. In addition, the design is simple, easy to manufacture, and various materials can be used for the fuel cell body material, and the volume and weight are smaller than those of a phosphoric acid fuel cell having the same principle of operation. In addition to these characteristics, the polymer electrolyte fuel cell can be applied to a wide variety of fields such as power source for non-polluting vehicles, locally installed power generation, space power, mobile power, and military power.

The main components of the polymer electrolyte fuel cell are a polymer electrolyte membrane, an anode and a cathode, and a separator for forming a stack. In particular, a membrane-electrode assembly (MEA) in which an anode and a cathode are adhered to a polymer electrolyte membrane by a hot-pressing method is called a membrane-electrode assembly (MEA) .

In addition, the fuel cell stack is formed by laminating several tens or hundreds of single cells where an electrochemical reaction takes place. In order to reduce the contact resistance between the unit cells and the stack, the end plates are tie rods Or air pressure. Both ends are equipped with connections for the outlet and inlet of the reactant gas, the coolant circulation and electric power output. In addition to these stacks, it consists of a fuel reformer, an air compressor, a heat and water processor, and a power converter.

A fuel cell is an organ that generates electricity incidentally with the production of electricity in the electrochemical reaction of hydrogen and oxygen. In order to use a fuel cell as an automobile engine, a stack of several tens kW is used. As the capacity of the fuel cell is increased, the amount of heat generated per unit volume increases, so that the importance of cooling is increasing.

Among the antifreeze used in the fuel cell stack, ethylene glycol is widely used as an antifreeze solution due to freezing point and low freezing point. When ethylene glycol is used as an antifreeze of a fuel cell, It is possible that leakage of the antifreeze may occur through the path of the adhesion part and the like. In this case, the chemical reaction of hydrogen and oxygen may be directly affected. Therefore, if the antifreeze is leaked and performance deteriorates, the stack must be separated to replace or repair the electrolyte membrane, electrode, gas diffusion layer, and bipolar plate.

Accordingly, the present inventors have found a new method of recovering the performance of a fuel cell using water and air without decomposing the stack and the unit cell when the performance of the fuel cell is reduced due to leakage of the antifreeze or cooling water, Completed.

Korean Patent No. 0766155

In order to solve the above problems, an object of the present invention is to provide a method for restoring the performance of a fuel cell without disassembling a stack and a unit cell when an antifreeze or cooling water is leaked in a polymer electrolyte fuel cell.

The present invention also provides a performance recovery device for a polymer fuel cell capable of restoring the performance of a fuel cell without disassembling the stack and the unit cell when the antifreeze or cooling water is leaked in the polymer electrolyte fuel cell.

In order to solve the above problems, the present invention provides a method for restoring the performance of a fuel cell without disassembling a stack and a unit cell in the case of leakage of antifreeze or cooling water in a polymer electrolyte fuel cell, And the performance of the poisoned catalyst is restored by injecting water into the fuel cell.

In one embodiment of the present invention, when 1 L of water is injected into the anode inlet and the cathode inlet, the performance of the fuel cell can be restored to 70 to 80% of the initial performance.

The present invention also relates to a method of recovering the performance of a fuel cell without decomposing a stack and a unit cell when an antifreeze or cooling water is leaked in a polymer electrolyte fuel cell. The method includes injecting air into the anode electrode, And recovering the performance of the poisoned catalyst.

In an embodiment of the present invention, when air is injected into the anode electrode and hydrogen is injected into the cathode electrode, an oxygen reduction reaction is generated at the anode to generate water in the electrode, thereby recovering the poisoned catalyst.

In an embodiment of the present invention, when air and hydrogen are injected for 12 hours, the performance of the fuel cell can be restored to 90 to 99% of the initial performance.

In one embodiment of the present invention, the antifreeze may be ethylene glycol.

According to another aspect of the present invention, there is provided a polymer electrolyte fuel cell in which porous anodes and cathodes are mounted on both sides of a polyelectrolyte membrane, and a hydrogen passage and an air passage are mounted on the anode and the cathode, The performance of the polymer fuel cell can be restored by injecting water into the gas inlet constituting the anode and the gas inlet constituting the cathode when the performance of the fuel cell is degraded.

The present invention also provides a polymer electrolyte fuel cell in which a porous anode and a cathode are mounted on both sides of a polymer electrolyte membrane, and a hydrogen passage and an air passage are mounted on the anode and the cathode, The performance of the polymer fuel cell can be restored by injecting air into the gas inlet of the anode and injecting hydrogen into the gas inlet of the cathode. to provide.

The present invention provides a method for recovering performance of a fuel cell by recovering a catalyst poisoned by leakage of an antifreeze or cooling water of a fuel cell. The performance of the fuel cell can be restored. Therefore, the fuel cell can be more effectively used as a fuel cell than the conventional fuel cell.

1 is a diagram showing a current-voltage repetitive operation.
FIG. 2 is a graph showing the results of fuel cell performance recovery experiments by current-voltage repetitive operation.
FIG. 3 is a view showing a performance recovery step using water. FIG.
FIG. 4 shows the results of fuel cell performance recovery experiments by water injection.
5 is a view showing a performance recovery step using air.
FIG. 6 is a graph showing the results of fuel cell performance recovery experiment through water production reaction by air injection.

The present invention is characterized in that when the antifreeze leaks through the fuel (hydrogen) inlet and the air inlet and flows into the fuel cell, the performance of the fuel cell can be restored without disassembling the stack and the unit cell have.

When the antifreeze used in the fuel cell stack leaks through the path of the separator adhered part or the like, the leaked antifreeze reacts with water molecules by the catalyst to become formic acid, and the formic acid molecule adsorbs to the active site of the catalyst, After being adsorbed to the active site, it is transformed to CO form and poison the active site of the catalyst. Also, other active sites meet with water molecules to form hydroxy groups. When CO adsorbed on the catalyst and hydroxyl groups meet, carbon dioxide and protons are formed and the catalytically active sites are recovered.

On the other hand, the present inventors confirmed that the reduction in the anode performance was significantly greater than that of the cathode through the results of the poisoning and decryption of the catalyst described above, and the results were used as a result of the anode.

The performance recovery method of the fuel cell according to the present invention is as follows.

First, the performance of the fuel cell can be restored by the current-voltage repetitive operation in order to recover the catalytic active site.

As a result of the current-voltage repetitive operation test according to the present invention, it is possible to restore the catalytic active site by restricting the amount of water flowing to the diffusion during the current voltage repetitive operation, thereby recovering the performance of the fuel cell.

(1) 1600 mA / cm ² of hydrogen (417.9 mL / min) and air (1326.7 mL / min) of the current-voltage repetitive operation are described in more detail. Is added. At this time, the flow rate of the hydrogen / air is proportional to the electrode area and the number of electrodes based on a 25 cm ² electrode. For example, the flow rate is @ 1600 mA / cm ² , the 5 cm ² electrode is 417.9/5, If it is 417.9x5. Lt; / RTI > Also, the flow rate of hydrogen and air is calculated as the stoichiometric ratio 1.5 / 2.0, and the amount of hydrogen and air required for the hydrogen oxidation reaction and the oxygen reduction reaction in the platinum catalyst is calculated as 1.0. Generally, the maximum performance is not more than 1600 mA / cm ² at 0.4V. (2) When hydrogen and air are injected into the fuel cell, an open circuit voltage (OCV) is formed. OCV is usually formed between 0.9 and 1.2V. (3) After OCV reaches the equilibrium state, the circulating voltage method is repeated. OCV ~ 0.4 V is repeated (0.9-0.8-0.7-0.65-0.6-0.55-0.5-0.45-0.4 V), and OCV is 0.4V , The voltage is maintained for 5 seconds in each voltage section, then moved to the next voltage. When the voltage reaches 0.4 V, the voltage is maintained at 0.4 V for 5 minutes and then moved to the next voltage. If it goes from 0,4V to OCV, it keeps 10 seconds in each voltage interval and then moves to the next voltage. When it reaches OCV, it keeps 30 seconds in OCV and then moves to the next voltage. Set the OCV to 1 cycle for the next OCV of 30 seconds and check the maximum current density available for each voltage. (4) Next, the above condition is maintained for about 12 hours, and it is confirmed whether the current density increases as a whole by collecting the current density in each voltage section. If the current density becomes equal to the equilibrium state after 12 hours, Lt; / RTI > Also, after 12 hours, when the current density tends to increase, it extends until it reaches an equilibrium state. However, it is better to select the appropriate time because the recovery efficiency decreases for a long time operation.

In the current-voltage method according to the present invention, the current density may be 1000 to 1500 mA / cm ² , and the voltage may be 0.8 to 1.0 V.

The current-voltage method according to the present invention can be performed for 10 to 14 hours. According to an embodiment of the present invention, the performance recovery of the fuel cell is confirmed by repeating the operation for 12 hours.

Also, in the method of recovering the performance of the fuel cell during the leakage of the antifreeze and the cooling water provided by the present invention, the performance of the fuel cell can be restored by injecting water through the gas inlet of the anode and the cathode.

The fuel cell performance recovery method using such water can be performed through the system described in FIG.

Furthermore, the method of recovering the performance of the fuel cell according to the present invention can recover the performance of the fuel cell by injecting air into the anode and injecting hydrogen into the cathode to generate an oxygen reduction reaction.

The time for injecting air into the anode is preferably 10 to 14 hours.

As described above, the performance recovery method of the fuel cell according to the present invention can be effectively used as a new fuel cell performance recovery method in place of the performance recovery method of the fuel cell when the conventional antifreeze is leaked.

Hereinafter, the present invention will be described in more detail by way of examples. The following examples are merely preferred embodiments of the present invention, but the present invention is not limited by the following examples.

< Reference Example  1> Fuel cell catalyst by antifreeze Poisoning  Recovery Mechanism

The mechanisms of poisoning and recovery of fuel cell catalysts by ethylene glycol are as follows.

(CH ₂ OH) ₂ → (CH ₂ OH) _{2 ads} (1)

(CH ₂ OH) _{2 ads} → (: COH) ₂ (2)

(: COH) ₂ + 2H ₂ O → (HCOOH) _ads + 2H + 2e ^- (3)

Pt (HCOOH) _ads → Pt (CO) _ads + H ₂ O (4)

_{Pt + H 2 O → Pt (} OH) ads (5)

Pt (OH) _ads + Pt (CO) _ads → Pt + CO ₂ + H ⁺

The poisoning mechanism of ethylene glycol is the same as the above reaction formula. Ethylene glycol reacts with water molecules in the Pt catalyst to formic acid (see Scheme 3 above). This formic acid molecule is again adsorbed on the active site of Pt and changes to the CO form to attack the active site of Pt (see Scheme 4 above).

Water molecules are required to recover the poisoned Pt, and the recovery mechanism is the same as in the above reaction formula (5-6). The other Pt active sites meet with water molecules to form hydroxyl groups (-OH), where the CO and OH adsorbed on the Pt react to form CO ₂ and protons, restoring the Pt active site.

When ethylene glycol leaks from the fuel cell, a side reaction occurs at both the anode and the cathode, and the CO function of the Pt catalyst is lost by the poisoning of the Pt catalyst, thereby reducing the fuel cell performance. If the catalyst is contaminated, it is inevitable that the fuel cell stack should be disassembled to replace the electrode (MEA) or the entire stack. In the present invention, the resultant value of the anode electrode was used.

< Example  1>

Performance recovery through driving method

Fuel cells use a constant current mode (constant current flow regardless of load) to generate a stable current. If a decrease in performance due to leakage of ethylene glycol during operation of the fuel cell occurs, water molecules are needed like the recovery mechanism described in the above reference example. In the anode, water molecules generated at the cathode diffuse through the electrolyte membrane and pass to the anode. However, the amount of this water molecule is very small. Accordingly, as shown in FIG. 1, the voltage is operated at 0.8 to 1.0 V and the current is operated at the current-voltage repetition of 1000 to 1500 mA / cm ² , so that sufficient amount of water is supplied to the diffusion to achieve performance recovery.

As shown in FIG. 2, the fuel cell performance recovery performance by the current-voltage repetition operation described above is shown to recover about 61% of the initial performance after 12 hours of repeated operation. Therefore, it can be seen that when the antifreeze and the cooling water leaks, the performance of the fuel cell can be improved by the current-voltage repetitive operation.

< Example  2>

Performance recovery using water

When the performance degradation of the fuel cell occurs due to leakage of the antifreeze ethylene glycol during operation of the fuel cell, the performance of the fuel cell can be restored by using water. That is, as shown in FIG. 3, the operation of the fuel cell was stopped and 1 L of water was injected through the gas inlet of the anode electrode and the cathode electrode to enrich the water molecules, thereby restoring the poisoned catalyst to restore the performance of the fuel cell.

As shown in FIG. 4, the performance recovery using the water was recovered to about 77% of the initial performance after 1 L of water injection. Therefore, it can be seen that the performance recovery method using water during the leakage of the antifreeze and cooling water can improve the performance of the fuel cell.

< Example  3>

Performance recovery using air

When a decrease in performance due to leakage of ethylene glycol occurs during the operation of the fuel cell, as shown in FIG. 5, air is injected instead of hydrogen into one anode electrode, hydrogen is injected into the two cathode electrodes instead of air to generate an oxygen reduction reaction at the anode Water can be generated in the electrode, and the performance of the fuel cell can be restored by restoring the poisoned catalyst.

The results of the performance recovery of the fuel cell according to this method are shown in FIG. 6, and the performance is recovered to 92% of the initial performance after 12 hours of air injection. Therefore, it can be seen that the water generation reaction due to the air injection during the leakage of the antifreeze and the cooling water can improve the performance of the fuel cell.

The present invention has been described with reference to the preferred embodiments. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

Claims (8)

A method for recovering the performance of a fuel cell without disassembling a stack and a unit cell in the case of leakage of an antifreeze or cooling water in a polymer electrolyte fuel cell, wherein water is injected into an anode inlet and a cathode inlet of the fuel cell, And recovering the performance of the polymer fuel cell. The method according to claim 1,
Wherein the performance of the fuel cell is restored to 70 to 80% of the initial performance when injecting 1 L of water into the anode inlet and the cathode inlet. A method of recovering performance of a fuel cell without disassembling a stack and a unit cell in the case of leakage of an antifreeze or cooling water in a polymer electrolyte fuel cell, comprising the steps of injecting air into the anode electrode and injecting hydrogen into the cathode electrode And recovering the performance of the polymer fuel cell. The method of claim 3,
When air is injected into the anode electrode and hydrogen is injected into the cathode electrode,
Generating an oxygen reduction reaction at the anode to produce water at the electrode, thereby recovering the poisoned catalyst. 5. The method of claim 4,
Wherein the performance of the fuel cell is restored to 90 to 99% of the initial performance when air and hydrogen are injected for 12 hours. 3. The method according to claim 1 or 2,
Wherein said antifreeze is ethylene glycol. A polymer electrolyte fuel cell in which porous anodes and cathodes are mounted on both sides of a polyelectrolyte membrane, and a hydrogen passage and an air passage are mounted on the anode and the cathode,
Characterized in that water is injected into the gas inlet constituting the anode and the gas inlet constituting the cathode when the performance of the fuel cell deteriorates due to the leakage of the hydrogen flow path or the air flow path, Performance recovery device. A polymer electrolyte fuel cell in which porous anodes and cathodes are mounted on both sides of a polyelectrolyte membrane, and a hydrogen passage and an air passage are mounted on the anode and the cathode,
When the performance of the fuel cell is degraded due to the leakage of the hydrogen flow path or the air flow path, air is injected into the gas inlet constituting the anode, and hydrogen is injected into the gas inlet constituting the cathode, A performance recovery device for a polymer fuel cell.

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