A rapid method for initial activation of a proton exchange membrane fuel cell stack

Abstract

The application discloses a quick method for initial activation of a proton exchange membrane fuel cell stack. The method realizes initial quick activation of the stack by controlling the humidity of gas inlets of cathodes and anodes of the stack, gas inlet pressure of the cathodes and the anodes, metering ratio of the cathodes when the cathodes are starved, starvation time of the cathodes, current density of the cathodes when the cathodes are starved, loading and unloading speed of activation current and constant current time of high current. The application greatly shortens the time and hydrogen consumption of initial activation of the stack and reduces time cost and fuel cost by reasonably matching the humidity of gas inlets of the cathodes and the anodes, gas inlet pressure of the cathodes and the anodes, metering ratio of the cathodes when the cathodes are starved, starvation time of the cathodes, current density of the cathodes when the cathodes are starved, loading and unloading speed of activation current and constant current time of high current.

Description

Technical Field

[0001] This invention belongs to the field of fuel cells, and specifically relates to a rapid method for the initial activation of a proton exchange membrane fuel cell stack. Background Technology

[0002] A proton exchange membrane fuel cell (PEMFC) is a chemical device that directly converts the chemical energy of fuel into electrical energy. The fuel cell stack is the heart of the PEMFC, the site of the chemical reaction. The stack is assembled from multiple cells. After assembly, an activation process is required to enhance its performance. Generally, stack activation primarily focuses on activating the internal membrane electrode assembly (MEA). This process mainly includes: 1. Wetting the proton exchange membrane to improve its proton conductivity, thereby reducing cell resistance; 2. Establishing water, proton, and reactant gas transport channels to accelerate mass transport and improve reaction efficiency; 3. Optimizing the internal structure of the electrodes to improve the three interfaces (membrane, electrode, and reactive gas); 4. Enhancing the activity and utilization rate of the cathode catalyst layer.

[0003] Existing fuel cell stack initial activation technologies include constant current discharge activation, variable current discharge activation, hydrogen pump activation, hydrogen starvation, and constant voltage discharge activation. Using these technologies alone for initial activation results in excessively long activation times, leading to increased hydrogen consumption and consequently high time and fuel costs. While some activation schemes integrate different technologies to improve efficiency, the improvements are limited and significant room for improvement remains. This invention, through optimized control of anode and cathode intake humidity, anode and cathode intake pressure, cathode metering ratio during cathode starvation, cathode starvation time, cathode starvation current density, activation current loading / unloading rates, and high-current constant-current time, significantly reduces the initial activation time and fuel consumption of the fuel cell stack.

[0004] In existing technologies, wetting the proton exchange membrane is generally achieved by controlling the humidity of the gas inlet and applying or reducing high current. The establishment of water, proton and reactant gas transport channels is generally achieved by rapidly applying or reducing the load and controlling the gas inlet pressure. Optimizing the internal structure of the electrode and improving the three interfaces are achieved by rapidly applying or reducing the load and constant current discharge. Improving the activity and utilization rate of the cathode catalyst layer is generally achieved by hydrogen starvation, hydrogen pump effect and other methods. Summary of the Invention

[0005] This invention significantly shortens the initial activation time and hydrogen consumption of the fuel cell stack by rationally controlling the intake humidity of the cathode and anode, the intake pressure of the cathode and anode, the cathode metering ratio during cathode starvation, the cathode starvation time, the cathode starvation current density, the loading and unloading rate of the activation current, and the constant current time of high current. This reduces time and fuel costs.

[0006] The technical solution of this invention is as follows:

[0007] A rapid method for initial activation of a proton exchange membrane fuel cell stack is provided, which controls the inlet humidity of the cathode and anode, the inlet pressure of the cathode and anode, the cathode stoichiometric ratio during cathode starvation, the cathode starvation time, the cathode starvation current density, the loading and unloading rate of the activation current, and the constant current time of the high current to achieve rapid initial activation of the stack.

[0008] The steps are as follows:

[0009] During the activation process, the intake humidity of the anode and cathode of the synergistic fuel cell stack, the intake pressure of the anode and cathode, the cathode stoichiometric ratio during cathode starvation, the cathode starvation time, the cathode starvation current density, the loading and unloading rate of the activation current, and the constant current time of the high current are all considered.

[0010] The anode and cathode intake pressures are adjusted according to the cathode metering ratio during cathode starvation; the cathode starvation time is adjusted according to the cathode starvation current density and the cathode metering ratio during cathode starvation; the activation current loading and unloading rates are adjusted according to the anode and cathode intake pressures.

[0011] In the above method, the humidity range of the anode and cathode of the fuel cell stack is always controlled during the activation process: the anode inlet humidity is maintained at 40-100%, and the cathode humidity is maintained at 60-100%.

[0012] In the above method, during the activation process, it is necessary to control the anode and cathode inlet pressure range as follows: anode inlet pressure 160-280 kPa, cathode inlet pressure 140-260 kPa; at the same time, it is necessary to control the anode and cathode inlet pressure difference to be 10-30 kPa, and ensure that the anode inlet pressure is always greater than the cathode inlet pressure.

[0013] In the above method, the cathode stoichiometry ratio needs to be controlled between 0.5 and 1.7 during the activation process when the cathode is starved.

[0014] In the above method, the cathode starvation time needs to be controlled within 5-60 seconds during the activation process.

[0015] In the above method, the cathode starvation current density needs to be controlled between 0.1 and 1.5 A / cm during the activation process. 2 .

[0016] In the above method, the activation current loading and unloading rate needs to be controlled at 3-40A / s during the activation process.

[0017] In the above method, the constant current of high current needs to be controlled within 1-20 minutes during the activation process.

[0018] A rapid method for initial activation of a proton exchange membrane fuel cell stack, specifically comprising the following steps:

[0019] (1) Install the target activated stack onto the test bench, first purge the anode and cathode with nitrogen, then heat the stack to 70℃-80℃, control the anode inlet humidity and cathode inlet humidity. During the entire activation process, the anode inlet humidity is maintained at 40-100%, the cathode humidity is maintained at 60-100%, the anode metering ratio is maintained at 1.6-2.0, and the cathode metering ratio is maintained at 2.0-2.4 except when the cathode is starved during activation. The anode inlet pressure and cathode inlet pressure are 160-280kPa and 140-260kPa, respectively, except when the cathode is starved during activation.

[0020] (2) When the temperature and humidity of the fuel cell stack reach the target values, the current loading begins, and the loading and unloading rate is set to 3-40A / s;

[0021] Specifically: 1. First, apply the current to 2A / cm. 2 Maintain constant current for 1-20 minutes, then rapidly reduce the load to 0.3~0.5 A / cm. 2 The cathode metering ratio is reduced to 1~1.2, the anode inlet pressure and cathode inlet pressure are adjusted to 190kPa and 170kPa respectively, the cathode starvation time is 5-60s, after the cathode starvation time ends, the cathode metering ratio is restored to 2.0~2.2, and the anode inlet pressure and cathode inlet pressure are restored to the values ​​set in step (1); 2. Then the current is applied to 2.5A / cm 2 Maintain constant current for 1-20 minutes, then rapidly reduce the load to 0.6~0.8 A / cm. 2 The cathode metering ratio is reduced to 1~1.2, the anode inlet pressure and cathode inlet pressure are adjusted to 200~220kPa and 180~200kPa respectively, the cathode starvation time is 5-60s, after the cathode starvation time ends, the cathode metering ratio is restored to 2.0~2.2, and the anode inlet pressure and cathode inlet pressure are restored to the set values ​​in step (1); after completing steps 1 and 2, one round of activation test is completed. Repeat multiple rounds of activation test until the stack reaches the target performance, which is considered as activation completion.

[0022] This invention minimizes the wetting time of the proton exchange membrane by controlling the anode and cathode intake humidity and the high-current constant flow time within a suitable range. Rapid establishment of water, proton, and reactant gas transport channels is achieved through optimized current loading / unloading rates and controlled gas inlet pressure. The activity and utilization rate of the cathode catalyst layer are rapidly improved by optimizing the cathode stoichiometry, cathode starvation time, and cathode starvation current density. Finally, by optimizing the combination of anode and cathode intake humidity, anode and cathode intake pressure, cathode stoichiometry, cathode starvation time, cathode starvation current density, activation current loading / unloading rates, and high-current constant flow time, the total activation time and total hydrogen consumption are shortened, achieving rapid initial activation of the fuel cell stack.

[0023] In this invention, the current during high-current constant current is set according to the maximum tolerable current value and the load tolerable value of the test bench. When there are no limitations on the test bench, the highest current value when the stack does not trigger the minimum protection value of the voltage is used as the set value. The starvation current value is basically positively correlated with the cathode metering ratio during starvation. The larger the starvation current value, the higher the cathode metering ratio. During starvation, the cathode intake pressure is adjusted according to the size of the cathode metering ratio. The higher the cathode metering ratio, the higher the cathode intake pressure. The anode intake pressure is adjusted according to the cathode intake pressure to always keep the anode intake pressure higher than the cathode intake pressure by a certain value.

[0024] The advantages of this invention compared to existing technologies are:

[0025] 1. The intake humidity of the anode and cathode and the high current constant current time were optimized, shortening the wetting time of the proton exchange membrane;

[0026] 2. The combination of rapid current loading and unloading rate and control of gas intake pressure has been optimized, shortening the establishment time of water, proton and reactant gas transmission channels;

[0027] 3. The combination of cathode stoichiometry, cathode starvation time and cathode starvation current density during cathode starvation was optimized to achieve a rapid improvement in the activity and utilization rate of the polar catalyst layer;

[0028] 4. Finally, the anode and cathode intake humidity, anode and cathode intake pressure, cathode metering ratio during cathode starvation, cathode starvation time, cathode starvation current density, activation current loading and unloading rate, and high current constant current time were optimized to shorten the total activation time and the total hydrogen consumption, thereby achieving the goal of rapid initial activation of the fuel cell stack. Attached Figure Description

[0029] Figure 1 This is the activation time diagram in Example 1.

[0030] Figure 2 This is a comparison chart of hydrogen usage in Example 1.

[0031] Figure 3 This is the activation time diagram in Example 2.

[0032] Figure 4 This is a comparison chart of hydrogen usage in Example 2.

[0033] Figure 5 This is a flowchart of the present invention. Detailed Implementation

[0034] Example 1

[0035] The target activated fuel cell stack was installed on the test bench. The anode and cathode were purged with nitrogen for three minutes. The stack was then heated to 70°C. The humidity of the anode and cathode intake air was controlled at 100%. Throughout the activation process, the humidity of both the anode and cathode was maintained at 100%. The anode metering ratio was maintained at 1.8, and the cathode metering ratio, except during cathode starvation activation, was maintained at 2.2. The anode and cathode intake pressures, except during cathode starvation activation, were maintained at 250 kPa and 230 kPa, respectively. Once the stack temperature and intake humidity reached the target values, current loading was initiated. The loading / unloading rate was set to 20 A / s. 1. Initially, the current was loaded to 2 A / cm². 2 Maintain constant current for 5 minutes, then rapidly reduce the load to 0.3 A / cm. 2 The cathode metering ratio was reduced to 1.2, and the anode and cathode inlet pressures were adjusted to 190 kPa and 170 kPa, respectively. The cathode starvation time was 40 s. After the cathode starvation time, the cathode metering ratio was restored to 2.2, and the anode and cathode inlet pressures were restored to 250 kPa and 230 kPa, respectively. 2. Then, the current was applied to 2.5 A / cm. 2 Maintain constant current for 5 minutes, then rapidly reduce the load to 0.6 A / cm. 2 The cathode metering ratio is reduced to 1.2, and the anode and cathode inlet pressures are adjusted to 200 kPa and 180 kPa, respectively. The cathode starvation time is 40 seconds. After the cathode starvation time, the cathode metering ratio is restored to 2.2, and the anode and cathode inlet pressures are restored to 250 kPa and 230 kPa, respectively. Completing steps 1 and 2 is considered completing one round of activation testing. Multiple rounds of activation testing are repeated until the stack reaches the target performance, at which point activation is considered complete. Using this activation process, the stack reaches the target performance after 2 hours, indicating activation is complete. This is 20% or more faster than conventional activation methods, and hydrogen consumption is reduced by 15% or more (e.g., ...). Figure 1 and Figure 2 (As shown).

[0036] Example 2

[0037] The target activated fuel cell stack was installed on the test bench. The anode and cathode were purged with nitrogen for three minutes. The stack was then heated to 70°C. The anode inlet humidity was controlled at 80%, and the cathode inlet humidity at 70%. Throughout the activation process, the anode and cathode humidity were maintained at 70% and 80%, respectively. The anode metering ratio was maintained at 1.6, and the cathode metering ratio, except during cathode starvation activation, was maintained at 2.0. The anode and cathode inlet pressures, except during cathode starvation activation, were maintained at 240 kPa and 220 kPa, respectively. Once the stack temperature and inlet humidity reached the target values, current loading was initiated. The loading / unloading rate was set to 30 A / s. 1. Initially, the current was loaded to 2 A / cm². 2 Maintain constant current for 7 minutes, then rapidly reduce the load to 0.5 A / cm. 2 The cathode metering ratio is reduced to 1, and the anode and cathode inlet pressures are adjusted to 190 kPa and 170 kPa, respectively. The cathode starvation time is 30 s. After the cathode starvation time, the cathode metering ratio is restored to 2.0, and the anode and cathode inlet pressures are restored to 240 kPa and 220 kPa, respectively. 2. Then, the current is applied to 2.5 A / cm. 2 Maintain constant current for 7 minutes, then rapidly reduce the load to 0.8 A / cm. 2 The cathode metering ratio is reduced to 1, and the anode and cathode inlet pressures are adjusted to 220 kPa and 200 kPa, respectively. The cathode starvation time is 30 seconds. After the cathode starvation time, the cathode metering ratio is restored to 2.0, and the anode and cathode inlet pressures are restored to 240 kPa and 220 kPa, respectively. Completing steps 1 and 2 is considered completing one round of activation testing. Multiple rounds of activation testing are repeated until the stack reaches the target performance, at which point activation is considered complete. Using this activation process, the stack reaches the target performance in 1.8 hours, indicating activation is complete, which is 28% or more faster than conventional activation methods, and hydrogen consumption is reduced by 12% or more (e.g., ...). Figure 3 and Figure 4 (As shown).

[0038] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A rapid method for initial activation of a proton exchange membrane fuel cell stack, characterized in that, The specific rapid method comprises the following steps: (1) install the target activated stack to the test bench, first use nitrogen to blow the anode and cathode, then heat the stack to 70-80℃, control the anode inlet gas humidity and the cathode inlet gas humidity, during the whole activation process, the anode inlet gas humidity is kept at 40-100%, the cathode humidity is kept at 60-100%, the anode metering ratio is kept at 1.6-2.0, the cathode metering ratio is kept at 2.0-2.4 except for the cathode starvation activation, the anode inlet gas pressure and the cathode inlet gas pressure are kept at 160-280kPa and 140-260kPa respectively except for the cathode starvation activation; (2) when the temperature and the inlet gas humidity of the stack reach the target value, start the current loading, and the set loading and unloading rate is 3-40A / s; Specifically: the first step, first load current to 2A / cm 2 , constant current 1-20min, then quickly reduce to 0.3-0.5A / cm 2 , the cathode metering ratio is reduced to 1-1.2, the anode gas pressure and the cathode gas pressure are adjusted to 190kPa and 170kPa, the cathode starvation time is 5-60s, after the end of the cathode starvation time, the cathode metering ratio is restored to 2.0-2.2, the anode gas pressure and the cathode gas pressure are restored to the set value in step (1); the second step, then load current to 2.5A / cm 2 , constant current 1-20min, then quickly reduce to 0.6-0.8A / cm 2 , the cathode metering ratio is reduced to 1-1.2, the anode gas pressure and the cathode gas pressure are adjusted to 200-220kPa and 180-200kPa, the cathode starvation time is 5-60s, after the end of the cathode starvation time, the cathode metering ratio is restored to 2.0-2.2, the anode gas pressure and the cathode gas pressure are restored to the set value in step (1); after completing steps 1 and 2, a round of activation test is completed, and repeating multiple rounds of activation test until the stack reaches the target performance is considered as activation completion.

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