A method for activating a fuel cell membrane electrode

Abstract

The application provides a fuel cell membrane electrode activation method, and specifically comprises the following steps: (1) installing a fuel cell on a test bench, setting an anode gas as hydrogen, setting a cathode gas as nitrogen, purging the hydrogen and the nitrogen to the anode and the cathode respectively, and pre-humidifying the fuel cell; (2) controlling the temperature of the fuel cell to be 30-60 DEG C, and ensuring the relative humidity RH of the cathode and the anode of the fuel cell to be greater than or equal to 100% through pre-humidification; (3) replacing the cathode gas from nitrogen with air, performing forced discharge treatment on the fuel cell under the condition that the hydrogen metering ratio is 1.0-2.0 and the air metering ratio is less than or equal to 1.3, and operating the fuel cell at a constant voltage less than or equal to 0.3 V to activate the fuel cell membrane electrode. The technical scheme of the application solves the problems of long time consumption, incomplete activation, low catalyst utilization rate and large energy consumption in the existing fuel cell membrane electrode activation method.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and more particularly to a method for activating a fuel cell membrane electrode. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) have become a research hotspot due to their high conversion efficiency and pollution-free products. The membrane electrode assembly (MEA) is the core component of the PEMFC, and its optimization directly determines the performance of the PEMFC. A good MEA requires not only perfect material selection but also careful initial activation after fabrication. Newly prepared MEAs often have structural defects, including: during the mixing of catalyst and ionomers in the catalyst layer, ionomer clusters can coat the surface of catalyst particles, making it difficult for reactant gases to reach the catalyst surface, increasing the mass transfer resistance of the MEA; sulfonate groups in the ionomers can also poison the catalyst; during the first coat of the catalyst slurry, the solvent evaporates rapidly, creating gaps on the catalyst surface that facilitate gas conduction. However, depending on the required Pt loading of the MEA, the catalyst slurry needs to be sprayed (or scraped) multiple times on the proton exchange membrane, causing some gaps to become blocked, making it difficult for reactant gases to enter; and during the hot pressing process of the MEA, the applied pressure can also seal some pores. The structural defects of MEA itself require a good activation method to solve.

[0003] Currently, the most commonly used MEA activation method is the constant potential or constant current method, which uses forced high current discharge to generate a large amount of water that diffuses outward to open the water vapor channels in the MEA. However, this method has the following problems: running at high current for a period of time will consume a large amount of gas; the required battery temperature is high, consuming a large amount of electrical energy; the reaction rate is too fast, and Pt is easily oxidized to PtO at high potential, reducing the reaction efficiency; and once the current density decreases, the water in the MEA is not easily discharged quickly. Therefore, the existing activation methods have limited activation efficiency and cannot bring the MEA to its optimal state.

[0004] Current research on activation methods for fuel cells is still insufficient. Therefore, it is particularly important to develop an efficient, rapid, and energy-saving MEA activation method. Summary of the Invention

[0005] In view of the technical problems mentioned above in the existing fuel cell membrane electrode activation methods, such as long activation time, incomplete activation, low catalyst utilization, and high energy consumption, a fuel cell membrane electrode activation method is provided. During the activation process, a portion of the sulfonate ions that have a poisoning effect on Pt can be removed in time, which can shorten the activation time of the fuel cell membrane electrode and improve the activation efficiency, and is suitable for improving the performance of fuel cell membrane electrode components.

[0006] The technical means employed in this invention are as follows:

[0007] A method for activating a fuel cell membrane electrode includes the following steps:

[0008] (1) Install the fuel cell on the test bench, set the anode gas to hydrogen and the cathode gas to nitrogen, and purge the anode and cathode with hydrogen and nitrogen respectively to pre-humidify the fuel cell;

[0009] (2) Control the temperature of the fuel cell to 30-60℃, and ensure that the relative humidity RH of the cathode and anode of the fuel cell is ≥100% by pre-humidification;

[0010] (3) Replace the cathode gas with air. Under the conditions of hydrogen metering ratio of 1.0-2.0 and air metering ratio of ≤1.3, perform forced discharge treatment on the fuel cell to make the fuel cell operate at a constant voltage of ≤0.3V and activate the fuel cell membrane electrode.

[0011] Furthermore, in step (3), the current density generated by the fuel cell under constant voltage is observed during the activation of the fuel cell membrane electrode until the current density remains stable, indicating that the fuel cell membrane electrode has been fully activated.

[0012] Further, in step (1), the relative humidity of the hydrogen and nitrogen gas purging the anode and cathode is 100%, and the purging time is 30 min; in step (3), the relative humidity of the air is 100%.

[0013] Furthermore, the activation time for the fuel cell membrane electrode is 25 min to 40 min.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] 1. The fuel cell membrane electrode activation method provided by the present invention uses a lower battery temperature for activation: 1) At a lower temperature, supersaturation humidification is easier, and the water produced by the battery will not evaporate quickly, thereby providing more water film for the catalyst remaining in the electrode to facilitate proton conduction. The humidification time will also be shortened, making it more energy-efficient; 2) When activation is carried out at a lower temperature, the reaction efficiency of the catalyst will be appropriately slowed down to prevent Pt in the catalyst from being rapidly oxidized to PtO and reducing the reaction activity.

[0016] 2. The fuel cell membrane electrode activation method provided by this invention employs a lower forced voltage discharge: 1) When the fuel cell is in operation, some of the Pt or other noble metals in the catalyst will be oxidized into metal oxides (such as PtO), which leads to a decrease in catalyst activity. Lowering the electrode potential makes it easier for some PtO or other oxides to be reduced back to Pt, thereby improving catalyst efficiency; 2) Slurry dispersion can cause excessive -SO3H to coat the catalyst surface, affecting mass transfer and causing catalyst poisoning. A voltage ≤0.3V can remove excess -SO3H; 3) At lower voltages, a larger battery load will generate a large amount of water, forming a water film, which is beneficial for H2O. + The conduction.

[0017] 3. The fuel cell membrane electrode activation method provided by the present invention uses a lower cathode gas consumption, which can reduce the discharge current, control the battery heat generation rate, and save energy consumption.

[0018] 4. The fuel cell membrane electrode activation method provided by the present invention has a fast activation time, which can be completed in 25 min to 40 min, saving time and hydrogen costs.

[0019] Based on the above reasons, this invention can be widely promoted in the field of fuel cells. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This diagram illustrates the change in current density during the activation of a fuel cell membrane electrode using the fuel cell membrane electrode activation method described in this invention.

[0022] Figure 2 This is a comparison chart of the three polarization curves in Example 1. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] The present invention provides a method for activating a fuel cell membrane electrode, comprising activating the fuel cell membrane electrode under low temperature conditions by pre-humidifying the fuel cell and then activating it by a constant voltage discharge method with low metering ratio and low voltage.

[0025] Specifically, the following steps are included:

[0026] (1) Install the fuel cell on the test bench, set the anode gas to hydrogen and the cathode gas to nitrogen, and purge the anode and cathode with hydrogen and nitrogen respectively to pre-humidify the fuel cell;

[0027] (2) Control the temperature of the fuel cell to 30-60℃, and ensure that the relative humidity RH of the cathode and anode of the fuel cell is ≥100% by pre-humidification;

[0028] During the activation process, the temperature of the fuel cell is set below the normal operating temperature. The purpose is that at a lower temperature, it is easier for the fuel cell to become supersaturated and humidified, and the humidification time will be shorter, resulting in greater energy savings. When activation is carried out at a lower temperature, the reaction efficiency of the catalyst will be appropriately slowed down to prevent Pt in the catalyst from being rapidly oxidized to PtO and reducing the reaction activity.

[0029] (3) Replace the cathode gas with air. Under the conditions of hydrogen metering ratio of 1.0-2.0 and air metering ratio of ≤1.3, perform forced discharge treatment on the fuel cell to make the fuel cell operate at a constant voltage of ≤0.3V and activate the fuel cell membrane electrode.

[0030] Using a lower forced voltage discharge can make it easier for some PtO or other oxides in the catalyst to be reduced to Pt, thereby improving the catalyst utilization efficiency; at the same time, controlling the constant voltage ≤0.3V during the activation process can remove excess -SO3H on the catalyst surface and reduce the impact of -SO3H coating on the mass transfer of the membrane electrode.

[0031] Furthermore, in step (3), during the activation of the fuel cell membrane electrode, the current density generated by the fuel cell under constant voltage is observed until the current density stabilizes, indicating that the fuel cell membrane electrode has been fully activated. Figure 1 As shown.

[0032] Further, in step (1), the relative humidity of the hydrogen and nitrogen gas purging the anode and cathode is 100%, and the purging time is 30 min; in step (3), the relative humidity of the air is 100%.

[0033] Furthermore, using the activation method provided by this invention, the activation time for the fuel cell membrane electrode is 25 min to 40 min, and the activation time varies depending on the MEA material.

[0034] Preferably, the temperature of the fuel cell is controlled at 40°C, and it is operated at a constant voltage of 0.2V to 0.3V to activate the fuel cell membrane electrode, and the activation time of the fuel cell membrane electrode is 30 minutes.

[0035] The fuel cell membrane electrode activation method provided by this invention can accelerate the saturation humidification rate of the membrane electrode and slow down the PtO formation rate by utilizing low temperature; reduce PtO to Pt with low voltage, improve catalyst utilization efficiency, remove -SO3H to prevent poisoning, and increase H2O. + Conductivity; low metering ratio reduces discharge current, controls battery heat generation rate, and saves energy; thus solving key problems such as high energy consumption, long processing time, and low efficiency of traditional activation methods.

[0036] The following examples illustrate the fuel cell membrane electrode activation method and its technical effects according to the present invention.

[0037] Example 1

[0038] Before activation, the fuel cell was operated normally with hydrogen gas introduced at the anode and air introduced at the cathode. At the normal operating temperature of the fuel cell, the back pressure was adjusted to the required level, and the polarization curve I (e.g., ...) was obtained using a voltage scanning method. Figure 2 The test (shown) was conducted with a test voltage of OCV to 0.6V and a scan speed of 5mV / s.

[0039] The activation of the fuel cell membrane electrode using the activation method described in this invention specifically includes the following steps:

[0040] (1) Install the fuel cell on the test bench, set the anode gas to hydrogen and the cathode gas to nitrogen, purge the anode and cathode with hydrogen and nitrogen respectively, the relative humidity of hydrogen and nitrogen is 100%, the gas flow rate is 18L / h, the purging time is 30min, set the battery back pressure to 0kPa, and pre-humidify the fuel cell.

[0041] (2) Control the temperature of the fuel cell to 30-60℃, and ensure that the relative humidity RH of the cathode and anode of the fuel cell is ≥100% by pre-humidification;

[0042] (3) Replace the cathode gas from nitrogen with air with a relative humidity of 100%. Under the conditions of a hydrogen stoichiometric ratio of 1.8 and an air stoichiometric ratio of 1.1, perform forced discharge treatment on the fuel cell to make the fuel cell operate at a constant voltage of ≤0.3V and activate the fuel cell membrane electrode. During the activation of the fuel cell membrane electrode, observe the current density generated by the fuel cell under constant voltage until the current density is stable and unchanged, indicating that the fuel cell membrane electrode has been fully activated. Using the activation method provided in this embodiment, the activation time of the fuel cell membrane electrode is 25min to 40min.

[0043] (4) After activation, raise the fuel cell temperature to the normal operating temperature, adjust the battery back pressure to the required pressure, and perform polarization curve II (e.g. Figure 2 The test (shown) was conducted with a test voltage of OCV to 0.6V and a scan rate of 5mV / s. By comparing polarization curve I and polarization curve II, it can be seen that the activation method provided in this embodiment can achieve the activation of the fuel cell membrane electrode.

[0044] Table 1 shows a comparison of hydrogen consumption and activation time between the activation method provided in this embodiment and the traditional constant current activation method for the same type of MEA. It can be seen that the fuel cell membrane electrode activation method provided by this invention consumes less hydrogen and has a faster activation time, saving time and hydrogen costs.

[0045] Table 1

[0046]

[0047] Furthermore, the activation process was verified to be complete by repeating steps (1) to (3):

[0048] Repeat steps (1) to (3) to reactivate the fuel cell. In step (3), the operation time under constant voltage is 20 minutes. Then, the fuel cell temperature is raised to the normal operating temperature, the battery back pressure is adjusted to the required pressure, the test voltage is maintained at OCV~0.6V, the scan rate is 5mV / s, and the voltage scan method is continued to perform polarization curve III (e.g. Figure 2 (As shown) test, such as Figure 2 As shown, polarization curve III basically overlaps with polarization curve II, indicating that the activation of the fuel cell membrane electrode using the activation method provided in this embodiment has been relatively sufficient.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for activating a fuel cell membrane electrode, characterized in that, Specifically, the following steps are included: (1) Install the fuel cell on the test bench, set the anode gas to hydrogen and the cathode gas to nitrogen, and purge the anode and cathode with hydrogen and nitrogen respectively to pre-humidify the fuel cell; (2) Control the temperature of the fuel cell to 30-60℃ to prevent Pt in the catalyst from being rapidly oxidized to PtO and thus reducing the reaction activity. Ensure that the relative humidity RH of the cathode and anode of the fuel cell is ≥100% by pre-humidification. (3) Replace the cathode gas with air. Under the conditions of hydrogen stoichiometry of 1.0-2.0 and air stoichiometry of ≤1.3, perform forced discharge treatment on the fuel cell to make the fuel cell operate at a constant voltage of ≤0.3V and activate the fuel cell membrane electrode. Control the constant voltage to ≤0.3V during the activation process so that some PtO or other oxides in the catalyst can be more easily reduced to Pt, thereby improving the catalyst utilization efficiency. At the same time, remove excess -SO3H on the catalyst surface and reduce the impact of -SO3H coating on the mass transfer of the membrane electrode. The activation time for the fuel cell membrane electrode is 25 min to 40 min.

2. The fuel cell membrane electrode activation method according to claim 1, characterized in that, In step (3), the current density generated by the fuel cell under constant voltage is observed during the activation of the fuel cell membrane electrode until the current density remains stable, indicating that the fuel cell membrane electrode has been fully activated.

3. The fuel cell membrane electrode activation method according to claim 1, characterized in that, In step (1), the relative humidity of the hydrogen and nitrogen gas purging the anode and cathode is 100%, and the purging time is 30 min; in step (3), the relative humidity of the air is 100%.

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