Method for improving the electrocatalytic stability of platinum-carbon catalysts for oxygen reduction

Abstract

This invention discloses a method for improving the oxygen reduction electrocatalytic stability of a platinum-carbon catalyst, comprising the following steps: mixing powdered platinum-carbon catalyst with deionized water, stirring for a period of time to uniformly disperse the platinum-carbon catalyst in the deionized water to form a platinum-carbon catalyst aqueous solution, and then irradiating the platinum-carbon catalyst aqueous solution generated in step (1) with a non-focused pulsed laser. During the irradiation process, the platinum-carbon catalyst aqueous solution is continuously stirred. Through the method described in this invention, the oxygen reduction electrocatalytic stability of the platinum-carbon catalyst is effectively improved without changing the composition of the platinum-carbon catalyst or reducing its oxygen reduction electrocatalytic activity. No other elements are introduced, and the process is simple.

Description

Technical Field

[0001] This invention relates to the field of fuel cell fabrication, specifically to a method for improving the electrocatalytic stability of oxygen reduction in platinum-carbon catalysts. Background Technology

[0002] Major developed countries worldwide highly value the development of hydrogen energy from resource and environmental perspectives. Hydrogen fuel cells are considered a key breakthrough in realizing the vision of hydrogen energy development. They are power generation devices that directly convert the chemical energy of hydrogen and oxygen into electrical energy, offering advantages such as zero pollution, no noise, and high energy conversion efficiency. However, to achieve large-scale industrial application of hydrogen fuel cells, in addition to significantly reducing production costs, it is also necessary to substantially increase the battery's lifespan. The core unit of a hydrogen fuel cell is the membrane electrode assembly (MEA), and the catalyst is one of the three key materials of the MEA. The stability of the catalyst directly determines the stability of the MEA, thus affecting the overall lifespan of the battery.

[0003] The cathode of a hydrogen fuel cell is where the electrochemical reduction reaction of oxygen molecules occurs. Currently, the most commonly used cathode catalyst is the platinum-carbon catalyst. However, the electrocatalytic stability of existing platinum-carbon catalysts for oxygen reduction has not yet reached an optimal level and still cannot meet the requirements for large-scale commercial applications of hydrogen fuel cells. During the operation of hydrogen fuel cells, corrosion of the carbon support, migration and accumulation of platinum, and poisoning by impurities are several key factors leading to a decrease in the catalytic activity of platinum-carbon catalysts.

[0004] In existing technologies, the following methods are commonly used to improve the electrocatalytic stability of platinum-carbon catalysts for oxygen reduction: First, introducing transition metals such as Fe, Co, and Ni to form alloys with Pt. While this method does improve the electrocatalytic stability of Pt, after assembly into a membrane electrode, these metals can leach from the alloy surface during use, pass through the proton exchange membrane, and reach the anode of the membrane electrode, drastically reducing the overall durability of the membrane electrode. Second, introducing dopants such as N, P, and S into the carbon support. These elements effectively anchor Pt nanoparticles, preventing their migration and aggregation during catalysis. However, carbon supports doped with N, P, and S have poor resistance to electrochemical corrosion at high potentials in acidic media. Third, introducing appropriate amounts of oxides can enhance the catalyst's resistance to impurity poisoning. However, oxides have poor conductivity, which hinders electron conduction during catalysis, thus reducing the catalyst's electrocatalytic activity for oxygen reduction. Therefore, existing methods for improving the electrocatalytic stability of platinum-carbon catalysts by altering their composition all have certain drawbacks. Summary of the Invention

[0005] The main objective of this invention is to provide a method for improving the electrocatalytic stability of oxygen reduction in platinum-carbon catalysts, which can effectively solve the problems in the background art.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for improving the electrocatalytic stability of oxygen reduction of platinum carbon catalyst, comprising the following steps: step (1): mixing powdered platinum carbon catalyst with deionized water, stirring for a period of time to uniformly disperse the platinum carbon catalyst in the deionized water to form a platinum carbon catalyst aqueous solution; step (2): irradiating the platinum carbon catalyst aqueous solution generated in step (1) with a non-focused pulsed laser, and continuously stirring the platinum carbon catalyst aqueous solution during the irradiation process.

[0007] In the above technical solution, the mass ratio of platinum carbon catalyst to deionized water in step (1) is 1:(100~1000).

[0008] In the above technical solution, the time for non-focused pulsed laser irradiation of the platinum-carbon catalyst aqueous solution in step (1) is 2 to 20 minutes.

[0009] In the above technical solution, the unfocused pulsed laser in step (2) is a parallel light with a wavelength of 532nm, a spot diameter of 7mm, a pulse width of 7ns, a frequency of 2 to 20Hz, and an energy density of 20 to 150mJ / cm2.

[0010] Advantages of this invention:

[0011] (1) The present invention utilizes the instantaneous thermal effect generated by pulsed laser irradiation to enhance the interaction between platinum nanoparticles and carbon support, effectively alleviating the migration and aggregation of platinum nanoparticles during the catalytic process, thereby improving the electrochemical stability of the catalyst.

[0012] (2) The method described in this invention can effectively improve the oxygen reduction electrocatalytic stability of the platinum-carbon catalyst without changing the composition of the platinum-carbon catalyst or reducing its oxygen reduction electrocatalytic activity.

[0013] (3) The technical solution of the present invention improves the stability of platinum-carbon catalyst without introducing other elements, and the process is simple. Attached Figure Description

[0014] Figure 1 These are the results of the oxygen reduction electrocatalytic stability test of a 20wt% platinum-carbon catalyst before and after laser irradiation;

[0015] Figure 2 These are the results of the oxygen reduction electrocatalytic stability test of a 40wt% platinum-carbon catalyst before and after laser irradiation;

[0016] Figure 3 These are the results of the oxygen reduction electrocatalytic stability test of a 60wt% platinum-carbon catalyst before and after laser irradiation. Detailed Implementation

[0017] The present invention will now be described in detail with reference to the accompanying drawings.

[0018] The present invention provides a method for improving the electrocatalytic stability of oxygen reduction of platinum carbon catalyst, comprising the following steps: Step (1): Mixing powdered platinum carbon catalyst with deionized water, stirring for a period of time to uniformly disperse the platinum carbon catalyst in the deionized water to form a platinum carbon catalyst aqueous solution; Step (2): Irradiating the platinum carbon catalyst aqueous solution generated in step (1) with a non-focused pulsed laser, and continuously stirring the platinum carbon catalyst aqueous solution during the irradiation process.

[0019] Example 1:

[0020] This embodiment provides a method for improving the electrocatalytic stability of platinum-carbon catalysts for oxygen reduction. The specific steps of this method are as follows:

[0021] First, 50 mg of platinum-carbon catalyst (platinum mass ratio of 20%) was dispersed in 10 mL of deionized water and stirred for 30 min to ensure uniform dispersion of the catalyst in the deionized water.

[0022] Subsequently, the platinum-carbon catalyst aqueous solution was irradiated with an unfocused pulsed laser while the solution was stirred during the irradiation process. The pulsed laser was a parallel beam with a wavelength of 532 nm, a spot diameter of 7 mm, a pulse width of 7 ns, a frequency of 20 Hz, an energy density of 60 mJ / cm², and an irradiation time of 6 min.

[0023] Finally, the stability of the catalyst prepared according to the method of the invention was tested. When selecting the test scheme, since the half-wave potential is an important indicator reflecting the catalytic activity of Pt / C catalyst, the larger the value, the higher the electrocatalytic activity of the catalyst for oxygen reduction. In the process of catalyst stability testing, the decrease of half-wave potential can directly indicate the decay of catalyst catalytic activity. Therefore, for those skilled in the art, the change value of half-wave potential is often used to measure the electrocatalytic stability of the catalyst. The smaller the change value of half-wave potential, the higher the electrocatalytic stability of the catalyst for oxygen reduction. Therefore, the linear sweep voltammetry (LSV) was used to test the stability of the catalyst prepared according to the method of the invention. The specific test method is as follows: 6 mg of the platinum-carbon catalyst aqueous solution prepared in Example 1 was added to 2.97 mL of isopropanol. The mixed solution was ultrasonically treated for 10 min, and then 30 μL of Nafion solution with a mass ratio of 5% was added. The ultrasonic treatment was continued for another 10 min to obtain a catalyst slurry. Then, 10 μL of the catalyst slurry was dropped onto a working electrode with a diameter of 5 mm using a pipette. The platinum loading on the working electrode was 4.0 μg. Finally, an aqueous solution of platinum-carbon catalyst with an equal mass ratio was prepared as a control solution. After natural drying at room temperature, electrochemical tests were performed. The electrochemical test conditions were: rotation speed of 1600 r / min, electrolyte of 0.1 M oxygen-saturated perchloric acid aqueous solution, LSV curve scan rate of 10 mV / s, CV cycle potential range of 0.6–1.0 V (vs. RHE), scan rate of 100 mV / s, and number of cycles of 30,000.

[0024] Depend on Figure 1 It can be seen that after laser irradiation, the electrocatalytic activity of the 20wt% platinum-carbon catalyst for oxygen reduction reaction did not decrease, but the electrocatalytic stability was significantly enhanced. After 30,000 CV cycles, the half-wave potential of the 20wt% platinum-carbon catalyst after laser irradiation decreased by only 14mV, which is significantly lower than the 40mV of the 20wt% platinum-carbon catalyst before laser irradiation.

[0025] Example 2:

[0026] This embodiment provides a method for improving the electrocatalytic stability of platinum-carbon catalysts for oxygen reduction. The specific steps of this method are as follows:

[0027] First, 25 mg of platinum-carbon catalyst (platinum mass ratio of 40%) was dispersed in 10 mL of deionized water and stirred for 30 min to ensure uniform dispersion of the catalyst in the deionized water.

[0028] Subsequently, the platinum-carbon catalyst aqueous solution was irradiated with an unfocused pulsed laser while the solution was stirred during the irradiation process. The pulsed laser was a parallel beam with a wavelength of 532 nm, a spot diameter of 7 mm, a pulse width of 7 ns, a frequency of 10 Hz, an energy density of 80 mJ / cm², and an irradiation time of 10 min.

[0029] The platinum-carbon catalyst aqueous solution prepared in Example 2 was tested using the same testing method as in Example 1.

[0030] Figure 2 The figure shows the electrocatalytic stability test results of the 40wt% platinum-carbon catalyst before and after laser irradiation for oxygen reduction. As can be seen from the figure, the electrocatalytic activity of the 40wt% platinum-carbon catalyst for oxygen reduction did not decrease after laser irradiation. After 30,000 CV cycles, the half-wave potential of the 40wt% platinum-carbon catalyst before laser irradiation decreased by 60 mV, while the half-wave potential after laser irradiation only decreased by 28 mV, indicating that laser irradiation significantly enhanced the electrocatalytic stability of the 40wt% platinum-carbon catalyst.

[0031] Example 3:

[0032] This embodiment provides a method for improving the electrocatalytic stability of platinum-carbon catalysts for oxygen reduction. The specific steps of this method are as follows:

[0033] First, 20 mg of platinum-carbon catalyst (platinum mass ratio of 60%) was dispersed in 10 mL of deionized water and stirred for 30 min to ensure uniform dispersion of the catalyst in the deionized water.

[0034] Subsequently, the platinum-carbon catalyst aqueous solution was irradiated with an unfocused pulsed laser while the solution was stirred during the irradiation process. The pulsed laser was a parallel beam with a wavelength of 532 nm, a spot diameter of 7 mm, a pulse width of 7 ns, a frequency of 10 Hz, an energy density of 100 mJ / cm², and an irradiation time of 8 min.

[0035] Figure 3 The figure shows the electrocatalytic stability test results of the 60wt% platinum-carbon catalyst before and after laser irradiation for oxygen reduction. As can be seen from the figure, the electrocatalytic activity of the 60wt% platinum-carbon catalyst for oxygen reduction did not decrease after laser irradiation. After 30,000 CV cycles, the half-wave potential of the 60wt% platinum-carbon catalyst before laser irradiation decreased by 64 mV, while the half-wave potential after laser irradiation only decreased by 27 mV, indicating that laser irradiation significantly enhanced the electrocatalytic stability of the 60wt% platinum-carbon catalyst.

[0036] As can be seen from Examples 1-3, irradiating an aqueous solution of a platinum-carbon catalyst with a non-focused pulsed laser can effectively improve the oxygen reduction electrocatalytic stability of the platinum-carbon catalyst.

[0037] The structures, proportions, sizes, etc., shown in the accompanying drawings are only for illustrative purposes to aid those skilled in the art and to enable them to understand and read the invention. They are not intended to limit the conditions under which the invention can be implemented and therefore have no substantial technical significance. Any changes in proportions or adjustments in size, without affecting the effects and objectives of the invention, should still fall within the scope of the technical content disclosed in the invention. Without substantial changes to the technical content, such changes should also be considered within the scope of the invention's implementation.

Claims

1. A method for improving the electrocatalytic stability of oxygen reduction in platinum-carbon catalysts, characterized in that: Includes the following steps: Step (1): Mix the powdered platinum-carbon catalyst with deionized water, stir for a period of time to make the platinum-carbon catalyst uniformly dispersed in the deionized water, forming a platinum-carbon catalyst aqueous solution; Step (2): Irradiate the platinum-carbon catalyst aqueous solution generated in step (1) with a non-focused pulsed laser, and continuously stir the platinum-carbon catalyst aqueous solution during the irradiation process; The time for non-focused pulsed laser irradiation of the platinum-carbon catalyst aqueous solution is 2–20 min; The unfocused pulsed laser is a parallel light with a wavelength of 532nm, a spot diameter of 7mm, a pulse width of 7ns, a frequency of 2-20Hz, and an energy density of 20-150mJ / cm².

2. The method for improving the electrocatalytic stability of oxygen reduction in a platinum-carbon catalyst according to claim 1, characterized in that: In step (1), the mass ratio of platinum carbon catalyst to deionized water is 1:(100-1000).

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