Rapid activation method of proton exchange membrane fuel cell

Abstract

The invention provides a rapid activation method of a proton exchange membrane fuel cell, and belongs to the technical field of fuel cells. The rapid activation method comprises a hydrogen pump activation stage and a variable load activation stage. In the hydrogen pump activation process, a current with the current density of 50-200mA / cm < 2 > is applied to the fuel cell in a constant current mode for 5-30 minutes, so that the utilization rate of an electrode catalyst is improved, and the generation of surface oxides of a cathode catalyst can be removed or avoided; in the variable load activation process, low current density and high current density are alternately changed, the ratio of the high current density to the rated current density of the battery is 0.8-1.2, and the ratio of the low current density to the high current density is less than or equal to 0.2, so that establishment of water, gas, electron and proton channels in the membrane electrode is facilitated. By adopting the activation method provided by the invention, the activation time of the proton exchange membrane fuel cell is effectively shortened, the hydrogen consumption is reduced, and the manufacturing cost of the fuel cell is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of fuel cells, and in particular to a rapid activation method for a proton exchange membrane fuel cell. Background Art

[0002] As an important part of the layout of hydrogen energy society, proton exchange membrane fuel cells are widely used in civil and military fields such as automobile engines, mobile power stations and submarine power systems due to their advantages such as high efficiency, zero emissions and low noise. At present, the large-scale industrialization process of fuel cells still faces problems such as cost, durability and performance. The initial performance of newly manufactured and assembled fuel cells is poor, and they must be intervened through a specific activation process to gradually improve the battery performance and achieve stability.

[0003] During the activation process of fuel cells, its mechanism of action includes the improvement of catalyst utilization, the wetting of proton exchange membranes, and the establishment of effective transmission channels for water, gas, electrons, and protons in the membrane electrode. Traditional fuel cell activation methods generally have problems such as long time consumption, low efficiency, and high hydrogen consumption, and are not suitable for large-scale and large-batch application scenarios. With the rapid development of hydrogen fuel cell industrialization, the number of fuel cell users continues to increase. It is urgent to develop a rapid activation method for proton exchange membrane fuel cells to shorten the activation time, reduce hydrogen consumption, improve activation efficiency, and reduce activation costs. Summary of the invention

[0004] In view of the technical problems existing in the background technology, the present application provides a rapid activation method for a proton exchange membrane fuel cell, aiming to solve the technical problems of the existing fuel cell activation method, such as long time consumption, high hydrogen consumption and low activation efficiency.

[0005] In a first aspect, an embodiment of the present application provides a method for rapid activation of a proton exchange membrane fuel cell, comprising the following steps: S1. Introduce inert gas into the anode and cathode of the fuel cell to purge the battery to a preset operating temperature and keep it stable; S2. Apply a constant current to the fuel cell for 5 to 30 minutes to activate the hydrogen pump, wherein the constant current density is 50 to 200 mA / cm 2 ; S3, connecting the fuel cell to an electronic load for several cycles of variable load activation until the fuel cell is fully activated and the activation is terminated; The specific steps of the variable load activation in each cycle include: first setting the load current to a first current density, maintaining it for 2 to 5 minutes, and then setting the load current to a second current density, maintaining it for 2 to 5 minutes; the ratio of the second current density to the rated current density of the fuel cell is 0.8 to 1.2; the ratio of the first current density to the second current density is ≤0.2.

[0006] The present invention provides a method for rapid activation of a proton exchange membrane fuel cell, which increases the utilization rate of the catalyst and improves the performance of the membrane electrode assembly by applying a constant current through an external power supply to perform hydrogen pump activation to promote changes in the electrode structure; and performs variable load activation by alternating between a first current density (low current density) and a second current density (high current density) to improve the wetting degree and gas-liquid transmission characteristics of the proton exchange membrane, thereby achieving rapid and stable improvement in battery performance.

[0007] In the present invention, the constant current density range in step S2 is 50~200mA / cm 2 , for example 50mA / cm 2 、80mA / cm 2 , 100mA / cm 2 , 120mA / cm 2 , 150mA / cm 2 , 180mA / cm 2 or 200mA / cm 2 The above numerical range is not limited to the above numerical values, and other numerical values ​​not listed are also applicable.

[0008] Theoretically, the reaction rate of hydrogen pump activation depends on the size of the applied current density. Following Faraday's law, a higher current density can ensure that sufficient hydrogen is produced on the cathode side of the battery and accelerate the removal of oxide impurities on the electrode surface. However, excessive current density will cause excessive water loss on the anode side and a decrease in proton conductivity.

[0009] Hydrogen pump activation time control: The membrane electrodes from the same production batch and with the same specifications can be pre-treated with a tentative 30-min hydrogen pump activation treatment, and a polarization curve test can be performed every 5 minutes. The efficiency of hydrogen pump activation at different stages can be calculated based on the test results. This operation facilitates the targeted setting of the appropriate hydrogen pump activation time, so that the battery can fully utilize the benefits of the hydrogen pump activation process in a shorter time.

[0010] Preferably, the inert gas in step S1 includes at least one of nitrogen, argon and helium.

[0011] Preferably, the preset working temperature in step S1 is 60-80°C. The preset working temperature should be within the working temperature range of the fuel cell, i.e., between 60-80°C, such as 60°C, 65°C, 70°C, 75°C or 80°C, etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable. If the preset working temperature is too low, the electrode catalyst activity is low and the electrode reaction rate is slow; if the preset working temperature is too high, the evaporation of water in the membrane is accelerated, which will increase the resistance to proton conduction.

[0012] Preferably, before activating the hydrogen pump in step S2, humidified hydrogen is introduced into the anode of the fuel cell, and humidified nitrogen is introduced into the cathode.

[0013] Preferably, the relative humidity of the humidified hydrogen is 100% to 150%, and the relative humidity of the humidified nitrogen is 100% to 150%; for example, 100%, 120%, 140% or 150%, etc., but are not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0014] Preferably, before activating the hydrogen pump in step S2, humidified hydrogen is introduced into the anode of the fuel cell at a constant flow rate, and humidified nitrogen is introduced into the cathode at a constant flow rate.

[0015] In the present invention, the workbench supplies gas to the fuel cell at a constant flow rate, and the battery undergoes an electrochemical hydrogen pump reaction. No water is produced during the reaction of the electrochemical hydrogen pump, and the humidified reaction gas can reach the catalyst surface through the diffusion layer to moisten the membrane, promote the hydration of the membrane, and thus reduce the proton conduction resistance. However, if the relative humidity is too high, liquid water condenses and covers the surface and pores of the diffusion layer and the catalyst layer, hindering the transmission of gas.

[0016] Preferably, before the load-variable activation in step S3, humidified hydrogen is introduced into the anode of the fuel cell, and humidified air or humidified oxygen is introduced into the cathode.

[0017] Preferably, in step S3, the stoichiometric ratio of humidified hydrogen to humidified air or oxygen is kept constant.

[0018] In the present invention, the relative humidity and stoichiometric ratio of the cathode and anode gases introduced in step S3 can be selected according to the flow channel type, operating conditions, experimental equipment, etc., so that the cathode and anode of the battery have sufficient reaction gas supply during the activation process to ensure the stability of the battery operation.

[0019] Preferably, the second current density in the variable load activation in step S3 is the rated current density of the fuel cell.

[0020] Preferably, the method for determining whether the battery is sufficiently activated in step S3 is: after two consecutive cycles of variable load activation, the absolute value of the voltage difference of the fuel cell at the second current density is less than 5mV, and the fuel cell is determined to be sufficiently activated.

[0021] Variable load activation time control: If the voltage difference of the fuel cell at the second current density is less than 5mV after two consecutive rounds of variable load activation cycles, the battery is considered to be fully activated and the variable load activation is terminated.

[0022] In the present invention, the current density of the variable load activation in step S3 varies widely and is carried out cyclically. The battery undergoes a cyclic operation from low to high current density, gradually increasing the diffusion of water in the membrane and the speed of proton transfer. The electrode reaction produces sufficient water, while promoting the establishment and optimization of water, gas, proton, and electron transmission channels inside the membrane electrode, and the activation effect is more comprehensive; and the time of 2 to 5 minutes under different current densities avoids the occurrence of flooding during activation, reducing the impact of water accumulation on the battery. In addition, the rate of loading or unloading when the load current is variable can be adjusted according to the actual battery reaction area and experimental equipment; on the premise of ensuring that the auxiliary system can stably respond to current changes, a faster loading rate can reduce the time required for activation and reduce the consumption of reaction gas.

[0023] Compared with the prior art, the present invention has the following beneficial effects: (1) The activation method provided by the present invention adopts a two-stage activation method, and the activation mechanism and target of each stage are different, which can improve the battery performance to a greater extent. During the hydrogen pump activation process, it is beneficial to improve the utilization rate of the electrode catalyst and remove or avoid the generation of oxides on the surface of the cathode catalyst; during the variable load activation process, low current density and high current density change alternately, which is beneficial to the establishment of water, gas, electron and proton channels in the membrane electrode. The activation method provided by the present invention effectively shortens the time required for the activation of the proton exchange membrane fuel cell, reduces the amount of hydrogen used, and reduces the manufacturing cost of the fuel cell.

[0024] (2) The activation method provided by the present invention is simple to operate and easy to implement, has the prospect of being applicable to large-scale fuel cell activation processes, and has certain commercial value. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic flow chart of a rapid activation method for a proton exchange membrane fuel cell according to Example 1 of the present invention; Figure 2 The relationship between the current density and time during the variable load activation process in Example 1 of the present invention; Figure 3 The polarization curves of the fuel cell after activation by the activation methods of Example 1 of the present invention and Comparative Example 1 are shown. DETAILED DESCRIPTION

[0026] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0027] If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0028] The fuel cell to be activated used in each embodiment and comparative example of the present invention is a fuel cell with an active area of ​​50 cm 2 Single cell (rated current density: 1600 mA / cm 2 ), the bipolar plate uses a graphite carbon plate with a parallel flow field.

[0029] Example 1 Figure 1 This is a schematic diagram of the process of activating the fuel cell in this embodiment. The specific activation steps are as follows: S1. Check the air tightness of the assembled fuel cell and then connect it to the fuel cell test bench; open the nitrogen valve, and pass nitrogen into the anode and cathode for purge respectively, and wait for the battery to reach 60°C and remain stable; S2. Hydrogen pump activation: Connect the anode of the fuel cell to the positive pole of the power supply, and the cathode to the negative pole of the power supply. A flow rate of 250 cc / min of hydrogen with a relative humidity of 100% is introduced into the anode, and a flow rate of 250 cc / min of nitrogen with a relative humidity of 100% is introduced into the cathode. The power supply applies 10 A (200 mA / cm 2 ) current, the battery undergoes an electrochemical hydrogen pump reaction, and this process lasts for 15 min; S3, variable load activation: disconnect the battery from the power supply, and connect the battery to the electronic load, continue to add humidified hydrogen with a relative humidity of 100% to the anode, and introduce oxygen with a relative humidity of 100% to the cathode, and maintain the stoichiometric ratio of the anode and cathode gases at 1.5 / 2 to supply gas to the battery; the battery is subjected to a variable load activation process by controlling the load current. The change of the current density over time in this process is shown in Figure 2 As shown, set the load current to 200 mA / cm 2 The battery was operated stably at this current density for 2 min; then the load current was set to 1600 mA / cm 2 And run stably at this current density for 5 min; S4, repeat the operation of S3 once, test the fuel cell at 1600 mA / cm after two consecutive cycles of variable load activation 2 When the absolute value of the voltage difference under the current density is less than 5mV, the activation is completed.

[0030] The activation time of the fuel cell in this embodiment is 30.0 min. The polarization curves before and after the activation of the fuel cell are shown in Figure 3 As shown by Figure 3It can be seen that the performance of the battery is significantly improved after the two-stage activation, which verifies the feasibility of the activation method provided in this embodiment.

[0031] Example 2 The difference between this embodiment and embodiment 1 is that the activation time of the hydrogen pump in S2 is 13 minutes, and the remaining steps are the same as those in embodiment 1.

[0032] Example 3 The difference between this embodiment and embodiment 1 is that the hydrogen pump activation time is 17 minutes, and step S3 sets the load current to 200 mA / cm 2 The battery was operated stably at this current density for 2 min, and then the load current was set to 1600 mA / cm 2 The process was run stably at this current density for 4 min; the remaining steps were the same as those in Example 1.

[0033] Example 4 The difference between this embodiment and embodiment 1 is that the current density of the constant current in step S2 is 50 mA / cm 2 , the remaining steps are the same as those in Example 1.

[0034] Comparative Example 1 This comparative example uses membrane electrodes and plates with the same specifications as those in Example 1. The specific activation steps are as follows: The fuel cell with qualified airtightness was placed on the test bench. When the battery temperature reached 60°C, hydrogen with a relative humidity of 100% and a stoichiometric ratio of 1.5 was introduced to the anode, and the back pressure was 50 kPa; oxygen with a relative humidity of 100% and a stoichiometric ratio of 2 was introduced to the cathode, and the back pressure was 50 kPa. According to the technical requirements of the test bench, the current was loaded to 1800 mA / cm 2 , and the battery is activated at a constant current density until the battery voltage becomes stable (the fluctuation range of the battery voltage is within 5 mV within 1 h).

[0035] The activation time of the fuel cell in this comparative example is 120 min. The polarization curves before and after the activation of the fuel cell are as follows: Figure 3 shown.

[0036] Comparative Example 2 The difference between this comparative example and Example 1 is that the order of the hydrogen pump activation process in S2 and the variable load activation process in S3 is exchanged, and the remaining steps are the same as in Example 1.

[0037] Comparative Example 3 The difference between this comparative example and Example 1 is that only hydrogen pump activation is performed without variable load activation, the hydrogen pump activation time is 30 min, and the remaining steps are the same as those of Example 1. The specific activation steps are as follows: S1. Check the air tightness of the assembled fuel cell and then connect it to the fuel cell test bench; open the nitrogen valve, and pass nitrogen into the anode and cathode for purge respectively, and wait for the battery to reach 60°C and remain stable; S2. Hydrogen pump activation: Connect the anode of the fuel cell to the positive pole of the power supply, and the cathode to the negative pole of the power supply. A flow rate of 250 cc / min of hydrogen with a relative humidity of 100% is introduced into the anode, and a flow rate of 250 cc / min of nitrogen with a relative humidity of 100% is introduced into the cathode. The power supply applies 10 A (200 mA / cm 2 ) current, the battery undergoes an electrochemical hydrogen pump reaction, this process lasts for 30 min, and the activation is completed.

[0038] The polarization curves of the fuel cells activated by the activation methods provided in Examples 1 to 4 and Comparative Examples 1 to 3 of the present invention were tested before and after activation. The results are shown in Tables 1 and Figure 3 shown.

[0039] Table 1 Polarization curve test results of Examples 1 to 4 and Comparative Examples 2 to 3 (current density 1600 mA / cm²)

[0040] According to the test results of the polarization curves of the embodiments and comparative examples in Table 1, the performance improvement rate of comparative example 2 is relatively low, indicating that the activation effect of first hydrogen pump and then load change is better than the activation effect of first load change and then hydrogen pump; the performance improvement of embodiments 1 to 4 is generally better than that of comparative example 3, indicating that the two-stage combination activation of hydrogen pump and load change is more comprehensive than the single hydrogen pump activation and has a better activation effect.

[0041] Figure 3 Figure 1 is a polarization curve diagram of the fuel cell after activation of Example 1 and Comparative Example 1. Example 1 can achieve the performance of the battery after full activation in only 30 minutes, and the measured polarization curve is almost the same as the polarization curve after complete activation, indicating that the rapid activation method provided by the present invention can significantly reduce the time required for activation while ensuring battery performance.

[0042] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for rapid activation of a proton exchange membrane fuel cell, characterized in that: The following steps are involved: S1. Introduce inert gas into the anode and cathode of the fuel cell to purge the battery to a preset operating temperature and keep it stable; S2. Apply a constant current to the fuel cell for 5 to 30 minutes to activate the hydrogen pump, wherein the constant current density is 50 to 200 mA / cm 2 ; S3, connecting the fuel cell to an electronic load for several cycles of variable load activation until the fuel cell is fully activated and the activation is terminated; The specific steps of the variable load activation in each cycle include: first setting the load current to a first current density, maintaining it for 2 to 5 minutes, and then setting the load current to a second current density, maintaining it for 2 to 5 minutes; the ratio of the second current density to the rated current density of the fuel cell is 0.8 to 1.2; the ratio of the first current density to the second current density is ≤0.

2.

2. The rapid activation method of a proton exchange membrane fuel cell according to claim 1, characterized in that: In the step S1, the inert gas includes at least one of nitrogen, argon and helium.

3. The rapid activation method of a proton exchange membrane fuel cell according to claim 1, characterized in that: In the step S1, the preset working temperature is 60-80°C.

4. The rapid activation method of a proton exchange membrane fuel cell according to claim 1, characterized in that: In the step S2, humidified hydrogen is introduced into the anode of the fuel cell and humidified nitrogen is introduced into the cathode before the hydrogen pump activation.

5. The rapid activation method of a proton exchange membrane fuel cell according to claim 4, characterized in that: The relative humidity of the humidified hydrogen is 100% to 150%, and the relative humidity of the humidified nitrogen is 100% to 150%.

6. The method for rapid activation of a proton exchange membrane fuel cell according to claim 4, characterized in that: In the step S2, before the hydrogen pump activation is performed, humidified hydrogen is introduced into the anode of the fuel cell at a constant flow rate, and humidified nitrogen is introduced into the cathode at a constant flow rate.

7. The rapid activation method of a proton exchange membrane fuel cell according to claim 1, characterized in that: In step S3, humidified hydrogen is introduced into the anode of the fuel cell, and humidified air or humidified oxygen is introduced into the cathode before the load-variable activation is performed.

8. The method for rapid activation of a proton exchange membrane fuel cell according to claim 1, characterized in that: In the step S3, the second current density is the rated current density of the fuel cell.

9. The method for rapid activation of a proton exchange membrane fuel cell according to claim 1, characterized in that: In step S3, the method for determining whether the fuel cell is sufficiently activated is: After two consecutive cycles of variable load activation, the absolute value of the voltage difference of the fuel cell at the second current density is less than 5 mV, which indicates that the fuel cell is fully activated.

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