A method for rapid activation of a fuel cell

Abstract

The present application relates to the field of fuel cell, specifically to a kind of fuel cell quick activation method, comprising the following steps: S1, the anode and cathode of fuel cell are all connected into high humidity nitrogen and are purged;S2, activation procedure, including S21 and S22: S21, according to four from low to high activation current order in turn four activations are carried out in operating stack, each activation operation includes three "gas shortage-recovery" cycle and once manual stop stack test platform operation;S22, restart stack test platform, pull load to fourth activation current, according to the standard working condition of fourth activation current operation for a period of time, judge whether average single piece voltage fluctuation is ≤5mV, if yes, then execute step S3;S3, after activation procedure is completed, anode, cathode are connected into dry nitrogen and are purged.The present application shortens stack activation time under the premise of guaranteeing activation effect, reduces the complexity and energy consumption of activation operation, improves the large-scale production efficiency of fuel cell.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fuel cells, in particular to a fuel cell rapid activation method. BACKGROUND

[0002] The activation treatment of fuel cell stack plays an important role in achieving the best output performance of the stack. After the stack is assembled, it needs to be activated first to achieve the best performance. In addition, as the running time of the stack increases, the performance of the stack will also decrease, and through activation treatment, the performance of the fuel cell can be restored to a certain extent.

[0003] At present, the commonly used activation methods include current control method, voltage control method, hydrogen pump method and cathode starvation method, but there are the following shortcomings:

[0004] 1. The current control method and the voltage control method are relatively simple in operation method, but in order to achieve good activation effect, a long time is often needed, and the total activation treatment time is usually more than 2h, and the hydrogen consumption of the activation operation is also high. At the same time, for different types of stacks, the setting of the activation parameters needs to be verified again, otherwise effective activation may not be achieved.

[0005] 2. The hydrogen pump method needs to connect an external power supply to generate current, which increases the complexity and cost of the equipment, and is difficult to implement in some scenes without suitable power supply.

[0006] 3. The cathode starvation method can reduce the oxidation state platinum (Pt-Ox) on the surface of the catalyst to metallic platinum (Pt), thereby restoring the performance of the stack and achieving the activation effect. However, the cathode starvation method needs to change the cathode stoichiometry repeatedly for a large number of times, which is relatively high in operation complexity. At the same time, it is necessary to strictly control the activation current density, the cathode stoichiometry and the activation time and other parameters. If the parameters are not set properly, the cathode voltage may be lower than 0V and hydrogen evolution may occur, and the hydrogen-air mixture may produce high temperature, causing the effective area of the catalyst layer to decrease and the sintering of Pt, which may damage the performance and life of the battery. SUMMARY

[0007] The purpose of the present application is to solve the problems in the background art, and to provide a fuel cell rapid activation method, which can further shorten the activation time of the stack, reduce the complexity and energy consumption of the activation operation process, and improve the efficiency of the large-scale production of fuel cells.

[0008] The technical scheme of the present application is a fuel cell rapid activation method, comprising the following steps:

[0009] S1, pre-blowing process: high humidity nitrogen is introduced into the anode and cathode of the fuel cell for blowing;

[0010] S2, an activation procedure, comprising S21 and S22:

[0011] S21, sequentially performing four activations on the running stack in order of four activation currents from low to high, each activation operation comprising three "gas shortage-recovery" cycles and one manual stop of the stack test bench operation, wherein the fourth activation current is 100% I E , I E is the rated current of the stack;

[0012] S22, restarting the stack test bench, pulling the load to the fourth activation current, running for a period of time according to the standard working condition of the fourth activation current, judging whether the average single cell voltage fluctuation is ≤5mV, if not, returning to step S21, if yes, executing step S3;

[0013] S3, a post-purging procedure: after the activation procedure is completed, dry nitrogen is introduced into the anode and the cathode for purging.

[0014] Preferably, the first three activation currents are 15% I E , 25% I E , and 50% I E , in order from low to high.

[0015] Preferably, the activation operation comprises the following steps:

[0016] A1, running for a period of time according to the standard working condition corresponding to the activation current;

[0017] A2, performing three "gas shortage-recovery" cycles;

[0018] A3, increasing the anode hydrogen metering ratio and the stack inlet pressure, and reducing the cathode air metering ratio;

[0019] A4, the average single cell voltage of the stack output begins to drop, and when the voltage drops to a preset second voltage indication value, the "stop" button of the stack test bench is directly pressed to make it stop.

[0020] Preferably, in A1, running for 90s according to the standard working condition corresponding to the activation current.

[0021] Preferably, in step A2, the "gas shortage-recovery" cycle steps are as follows: keeping the anode hydrogen metering ratio unchanged, reducing the cathode air metering ratio from λca specified in the standard working condition of the activation current to 0.5λca, monitoring the stack output voltage, when the average single cell voltage of the stack output decreases to a preset first voltage indication value, immediately restoring the cathode air metering ratio to λca, at this time the voltage begins to rise, and after the average single cell voltage no longer continues to rise, continuing to run for 20s.

[0022] Preferably, the first voltage indication value is 0.15V and the second voltage indication value is 0.08V.

[0023] Preferably, in step A3, the anode hydrogen gas metering ratio is first increased from the standard working condition λan to 1.2λan, and the anode hydrogen gas inlet stack pressure is increased by 10 kPa compared with the standard working condition, and then the cathode air metering ratio is reduced from λca to 0.5λca.

[0024] Preferably, in step S22, the fourth activation current standard working condition is operated for 10 min.

[0025] Compared with the prior art, the present application has the following beneficial technical effects:

[0026] The present application can further shorten the stack activation time, reduce the complexity and energy consumption of the activation operation process, reduce the hydrogen consumption, reduce the cost, ensure the battery performance and service life, and is conducive to improving the large-scale production efficiency of fuel cells. The manual stop of the stack test bench operation plays a role in strengthening the cathode starvation effect, so that the activation effect can be achieved without relying on too many "air shortage-recovery" cycles as in the conventional cathode starvation operation.

[0027] The present method can significantly improve safety and avoid the risk of hydrogen evolution reaction caused by the voltage dropping to 0V (or below) due to the delayed recovery of the cathode air metering ratio during operation. The present method does not completely rely on the common "air shortage-recovery" cycle for activation, and the subsequent manual stop of the stack test bench operation can effectively reduce the possibility of generating local high temperature to harm the catalyst. When the voltage drops to the second voltage indication value, the stack test bench is stopped urgently, and the fuel cell is disconnected from the load immediately, so there is no risk of hydrogen evolution. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The present application provides a method flowchart. DETAILED DESCRIPTION

[0029] As shown in the figure, the present embodiment proposes a fuel cell rapid activation method, which comprises the following steps: Figure 1

[0030] S1, pre-blowing process: high humidity nitrogen is introduced into the anode and cathode of the fuel cell for blowing, and the proton exchange membrane is fully wetted by the water vapor in the gas, and the impurities attached to the surface of the catalyst are preliminarily blown away. It is recommended that the relative humidity of nitrogen be set to 80%-100%, and the blowing time be 3 min.

[0031] S2, activation process, comprising S21 and S22:

[0032] ​S21, four activations are performed in turn on the running stack according to the order of four activation currents from low to high, each activation operation includes three "gas shortage-recovery" cycles and one manual stop of the stack test bench operation, wherein the four activation currents are 15%I E , 25%I E , 50%I E and 100%I E from low to high, I E is the rated current of the stack.

[0033] The activation operation includes the following steps A1-A4:

[0034] A1, running according to the standard operating condition corresponding to the activation current for 90s.

[0035] A2, the "gas shortage-recovery" cycle steps are as follows: keeping the anode hydrogen metering ratio unchanged, reducing the cathode air metering ratio from λca specified by the standard operating condition of the activation current to 0.5λca, monitoring the stack output voltage, when the average single piece voltage of the stack output is reduced to a preset first voltage indication value (> 0V, for example, set to 0.15V), immediately restore the cathode air metering ratio to λca, at this time the voltage begins to rise, after the average single piece voltage no longer continues to rise, continue to run for 20s, the above process is one "gas shortage-recovery" cycle, a total of three "gas shortage-recovery" cycles are required.

[0036] A3, first increase the anode hydrogen metering ratio from λan of the standard operating condition to 1.2λan, the anode hydrogen inlet pressure is increased by 10kPa compared with the standard operating condition, and then reduce the cathode air metering ratio from λca to 0.5λca.

[0037] A4, the average single piece voltage of the stack output begins to drop, when the voltage drops to a preset second voltage indication value (> 0V, for example, set to 0.08V), directly press the "stop" button of the stack test bench to stop.

[0038] It should be noted that the cathode and anode metering ratios corresponding to different activation currents are different, and the standard metering ratios suitable for stack operation given by different stack manufacturers will be different, which is related to the design of the stack.

[0039] S22, restart the stack test bench and pull the load to the fourth activation current, i.e. 100%I E , run at the rated point according to the standard operating condition of the fourth activation current for 10min, judge whether the average single piece voltage fluctuation is ≤5mV, if not, reduce the load to the first activation current (15%I E ) and re-perform a new round of activation, return to step S21, if yes, it indicates that the activation is successful, and step S3 is executed.

[0040] During the whole activation process, the purging is not carried out again when the test bench is stopped and restarted each time to maintain the wetness of the proton membrane.

[0041] S3, post-purging process: after the activation process is completed, dry nitrogen is introduced into the anode and cathode for purging to remove excess water, facilitating the storage of the stack.

[0042] The method can further shorten the activation time of the stack, reduce the complexity and energy consumption of the activation operation process, reduce the hydrogen consumption, reduce the cost, ensure the performance and life of the battery, and improve the efficiency of the large-scale production of fuel cells.

[0043] Before the test bench is stopped, the hydrogen inlet pressure and the metering ratio (i.e. gas flow) of the anode are appropriately increased, and when the voltage is reduced to the set second voltage indication value, the flow of the anode hydrogen is significantly greater than that of the cathode air, and the pressure difference between the anode hydrogen and the cathode air is also greater than that during normal operation under standard conditions, which is more likely to cause a reducing chemical environment on the cathode side to repair the oxidized catalyst. Therefore, the manual stop of the test bench operation plays a role in strengthening the cathode starvation effect, so that it does not need to rely on too many times of "gas shortage-recovery" cycles as in the conventional cathode starvation operation to achieve a similar activation effect. Therefore, the method has fewer cycles of "gas shortage-recovery" operation, and the activation effect is strengthened by manually stopping the test bench operation, thereby ensuring the activation effect on the basis of reducing the number of "gas shortage-recovery" cycles.

[0044] In addition, for the traditional cathode starvation activation method, only the cathode side reaction gas has a metering ratio that changes repeatedly, which is beneficial to the removal of impurities and excess water in the catalyst and ionomer. The method proposed in the present application includes multiple manual stop operations of the test bench, and both the anode and the cathode gas have a process of rapid pressure reduction and gas stop from the running state, so it has good cleaning and purging function for impurities and excess water in the cathode and anode catalyst layers.

[0045] The difference between the two voltage indication values (first voltage indication value > second voltage indication value > 0V) can improve the ease of operation of the activation process and reduce the risk of local overheating caused by improper operation (voltage ≤ 0V) which may damage the fuel cell materials and performance.

[0046] The method makes the voltage indication value of the cathode air metering ratio changing from "lack of air" to "normal" higher than the traditional cathode starvation method (close to 0V to ensure activation effect), thereby significantly improving safety, avoiding hydrogen evolution reaction caused by voltage dropping to 0V (or below) due to the cathode air metering ratio not being restored in time during operation, and not completely relying on the common "lack of air-restoration" cycle to achieve activation. Subsequent manual stop of the stack test bench operation can make up for the lack of activation caused by starting to restore air supply at a higher voltage (first voltage indication value), effectively reducing the possibility of local high temperature damaging the catalyst. The second voltage indication value can be closer to 0V, comparable to the commonly used cathode starvation method setting value, or even lower, which can maximize the cathode starvation effect and almost eliminate the risk of hydrogen evolution. This is because when the voltage drops to this setting value, the stack test bench stops immediately, and the fuel cell is disconnected from the load.

[0047] The embodiments of the present application are described in detail above in combination with the drawings, but the present application is not limited thereto, and various changes can be made within the knowledge of those skilled in the art without departing from the spirit of the present application.

Claims

1. A method for rapid activation of a fuel cell, characterized by, The method comprises the following steps: S1, pre-blowing process: the anode and cathode of the fuel cell are both purged with high humidity nitrogen; S2, activation process, comprising S21 and S22: S21, in order from low to high, four activations are sequentially performed on the operating stack, each activation operation including three "gas shortage-recovery" cycles and one manual stop stack test bench operation, wherein the fourth activation current is 100% I E , I E is the rated current of the stack; S22, restart the test bench, pull the load to the fourth activation current, run for a period of time according to the standard working condition of the fourth activation current, and judge whether the average single piece voltage fluctuation is less than or equal to 5mV, if not, return to step S21, if yes, execute step S3; S3, post-blowing process: after the activation process is completed, dry nitrogen is introduced into the anode and cathode for blowing; The activation operation comprises the following steps: A1, run for a period of time according to the standard working condition corresponding to the activation current; A2, execute three "gas shortage-recovery" cycles; A3, increase the anode hydrogen metering ratio and the inlet pressure, and reduce the cathode air metering ratio; A4, the average single piece voltage of the stack output begins to drop, and when the voltage drops to a preset second voltage indication value, the "stop" button of the test bench is directly pressed to stop it; In step A2, the "gas shortage-recovery" cycle steps are as follows: the anode hydrogen metering ratio is kept unchanged, the cathode air metering ratio is reduced from λca specified by the standard working condition of the activation current to 0.5λca, the stack output voltage is monitored, when the average single piece voltage of the stack output decreases to a preset first voltage indication value, the cathode air metering ratio is immediately restored to λca, at this time the voltage begins to rise, and after the average single piece voltage no longer continues to rise, continue to run for 20s; The first voltage indication value is 0.15V, and the second voltage indication value is 0.08V; In step A3, the anode hydrogen metering ratio is first increased from λan of the standard working condition to 1.2λan, the anode hydrogen inlet pressure is increased by 10kPa compared with the standard working condition, and then the cathode air metering ratio is reduced from λca to 0.5λca.

2. The method of claim 1, wherein the fuel cell is activated in less than 30 minutes. The first three activation currents are 15% I E , 25% I E , and 50% I E , in order from low to high.

3. The method of claim 1, wherein the step of activating the fuel cell is performed in less than 30 minutes. In A1, run for 90s according to the standard working condition corresponding to the activation current.

4. The method of claim 1, wherein the fuel cell is activated in less than 30 minutes. In step S22, run for 10min according to the standard working condition of the fourth activation current.

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