CN116314871A - Preparation method of nickel cobalt selenide loaded platinum catalyst - Google Patents

Abstract

The invention discloses a preparation method of a nickel-cobalt-selenide-supported noble metal platinum catalyst. The structural unit uses carbon cloth as a carrier, nitrogen-doped carbon nanotubes as a conductive network, and nickel-cobalt-selenide as a deposition site. Deposition is used to load the platinum nano-clusters on the nickel-cobalt selenide, and the platinum nano-clusters are loaded on the surface of the nickel-cobalt selenide by an electrodeposition method to prepare a bifunctional nickel-cobalt selenide-supported platinum catalyst. The bifunctional catalyst of the present invention aims to utilize the synergistic effect between the transition metal selenide and platinum to enhance the adsorption gas adsorption efficiency and the catalytic performance of platinum, improve stability and electrical conductivity, and have a lower ORR and MOR reaction. The overpotential and cost can meet the requirements of commercial applications.

Description

A kind of preparation method of nickel cobalt selenide supported platinum catalyst

technical field

The invention belongs to the technical field of methanol catalysts, in particular to a preparation method of a nickel-cobalt-selenide-supported noble metal platinum catalyst.

Background technique

Nowadays, the world's energy is limited, and the unreasonable exploitation and waste of human beings have caused many problems such as energy crisis and environmental pollution. Most of the world's energy needs are solved by burning fossil fuels. The related consequences of air pollution, global warming, and the greenhouse effect are the subject of many debates among developed countries that are seeking a common legislation to properly limit pollution emissions and protect the environment. Transportation accounts for a large portion of the world's energy consumption and has a large impact on air pollution. Although modern vehicles emit fewer toxic gases and particulates than their predecessors, their increasing numbers contribute to rising levels of pollution from transportation sources; in the near future In the future, transport-related pollution levels could be reduced by replacing a large number of internal combustion engine vehicles with electric vehicles. In order to meet the needs of modern society and ecological health issues, finding efficient, clean and sustainable energy technologies is the focus of research in the field of energy in the world today.

Methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) are the core reaction processes of important renewable energy technologies, and their applications involve fuel cells, metal-air batteries, and hydrogen production from water electrolysis. Fuel cells can be divided into polymer electrolyte membrane fuel cells (PEMFC), alkaline fuel cells (AFC), solid oxide fuel cells (SOFC), phosphoric acid fuel cells (PAFC) and molten carbonate fuel cells according to the electrolyte used. battery (MCFC). PEMFCs perform well in many practical applications, such as the automotive industry, and are considered a pioneering fuel cell that uses hydrogen as fuel. However, hydrogen fuel is highly flammable, has transportation and storage problems, and hydrogen fuel is usually required to be under high pressure during operation. Once the hydrogen is not handled properly, it may lead to major accidents such as explosions, which is a related safety issue that cannot be ignored in PEMFC. Direct Methanol Fuel Cell (DMFC) is derived from PEMFC, and the fuel is methanol solution. Compared with PEMFC, DMFC has the unique advantage of being fueled by renewable liquid methanol, because methanol can be safely stored and transported, and also has high energy density (6100Wh kg ^-1 ). In addition, DMFC has a faster anodic reaction rate because the methanol oxidation reaction process does not destroy the CC bond. Alkaline fuel cells have high operating voltage, high current density, and the ability to use transition metals to replace noble metals, etc., have been extensively studied; hydrogen has higher energy than other fuels, followed by methanol, but there are few sources of hydrogen and a high risk factor, while methanol The source of fuel is abundant, the price is low, the energy conversion efficiency is high, and it is easy to carry. Therefore, the direct methanol fuel cell is an ideal energy cell in the fuel cell and has commercial application prospects. The key to making methanol produce MOR and ORR is the catalyst. There is poor catalytic effect.

Contents of the invention

In order to solve the above-mentioned technical problems, the object of the present invention is to provide a kind of preparation method of the bifunctional nickel-cobalt selenide supported platinum catalyst of high active specific surface area, good electrochemical performance, realize the synergistic effect of nickel-cobalt selenide and platinum, improve platinum The catalytic performance of the material is applied to MOR and ORR under alkaline conditions.

In order to realize the above-mentioned invention object, the present invention provides a kind of preparation method of bifunctional nickel-cobalt selenide supported platinum catalyst, described method is carrier with carbon cloth, with nitrogen-doped carbon nanotube (NCNTs) as conductive network, with nickel-cobalt The selenide is the deposition site, and the platinum nano-clusters are supported on the nickel-cobalt selenide by electrodeposition.

Further, the method specifically includes the following steps:

(1) Synthesis of cobalt-iron nanowires: using carbon cloth as a precursor, cobalt-iron nanowires were prepared from cobalt nitrate hexahydrate, ferric nitrate nonahydrate, ammonium fluoride and urea. Sonicate in 8-12wt.% potassium permanganate solution for 15-30 minutes, continue to sonicate in deionized water and ethanol until the solution is completely clear, dry at 50-80°C for 4-6 hours, and then arrange the carbon at 0.2-0.4 g cobalt nitrate hexahydrate, 0.2~0.3g ferric nitrate nonahydrate, 0.1~0.3g ammonium fluoride, 0.5~1.0g urea and 40~50mL deionized water mixed solution, stir to form a uniform mixed solution, transfer to hydrothermal In the reaction kettle, react at 125-135°C for 6-8 hours, take out the carbon cloth, wash it with deionized water and ethanol, and finally dry it in a vacuum oven at 50-60°C for 4-6 hours;

(2) Synthesis of nitrogen-doped carbon nanotubes: the carbon cloth for growing cobalt-iron nanowires and 1-2 g of dicyandiamide are placed in two different porcelain boats of the tube furnace, and the dicyandiamide is located in the tube furnace. Upstream, in an inert gas atmosphere, anneal at 400°C for 2 to 4 hours, continue to heat up to 700 to 800°C for 2 hours, and the rate of temperature increase is 3 to 5°C/min;

(3) Synthesis of nitrogen-doped carbon nanotube-supported nickel-cobalt hydroxide: grow nickel-cobalt double hydroxide on carbon nanotubes, specifically: arrange the carbon for growing nitrogen-doped carbon nanotubes at 1.0-2.0g In a mixed solution of cobalt chloride hexahydrate, 0.5-1.0g nickel chloride hexahydrate, 1.0-2.0g urea and 50-100mL deionized water, stir for 20-40min to form a uniform mixed solution, transfer it to a hydrothermal reaction kettle, React at 110-125°C for 6-8 hours, take out the carbon cloth, wash it with deionized water and ethanol, and finally dry it in a vacuum oven at 50-60°C for 6-8 hours;

(4) Synthesis of nitrogen-doped carbon nanotube-supported nickel-cobalt selenide: nickel-cobalt selenide is prepared from carbon cloth and selenium powder growing nickel-cobalt nanosheets, specifically: carbon cloth for growing nickel-cobalt nanosheets and 0.5 ～2.0g of selenium powder is placed in two different porcelain boats of the tube furnace, the selenium powder is located in the upstream of the tube furnace, heated to 400～800°C for 2～4h in an inert gas atmosphere, and the heating rate is 3 ~5°C/min;

(5) Synthesis of nickel-cobalt-selenide-supported platinum catalyst: the electro-deposition method was used to grow platinum nanoclusters on the surface of carbon cloth loaded with nickel-cobalt-selenide carbon nanotubes to obtain a bifunctional nickel-cobalt-selenide-supported noble metal platinum catalyst. Specifically: use carbon cloth loaded with nickel-cobalt-selenide as cathode, platinum sheet as anode, saturated calomel electrode as reference electrode, place 1-10mmol/L chloroplatinic acid and 50-60mmol/L dihydrogen phosphate Constant-pressure deposition in potassium solution for 1000-5000s, the carbon cloth is taken out, washed with deionized water and ethanol, and finally dried in a vacuum oven at 40-60°C for 6-24 hours.

The bifunctional nickel-cobalt-selenide-supported platinum catalyst of the present invention is applied to catalyze ORR and MOR, and the nickel-cobalt-selenide supported on the surface of nitrogen-doped carbon nanotubes can significantly enhance the gas adsorption efficiency of platinum nanoclusters and improve the stability and electrical conductivity, have high catalytic activity and cost in ORR and MOR reactions, and can meet the requirements of commercial applications.

Compared with the prior art, the bifunctional nickel-cobalt selenide supported platinum catalyst prepared by the present invention has the following beneficial effects:

(1) Nitrogen-doped carbon nanotubes can not only connect each other to form an excellent conductive network, improve the weakness of metal oxides with insufficient electrical conductivity, but also help to expose more electrochemically active substances on the surface of carbon nanotubes. Heterocarbon nanotube-supported nickel-cobalt-platinum selenide can make the catalyst have a high specific surface area and a stable three-dimensional network structure, and its special three-dimensional structure provides a good template for the efficient deposition of platinum nanoclusters, expanding the application field;

(2) Nickel-cobalt-selenide can provide more deposition sites, and has a synergistic effect with platinum, which is beneficial to improve the catalytic effect of platinum. Self-supporting nitrogen-doped carbon nanotube-supported nickel-cobalt-platinum selenide has more active sites points and higher catalytic performance, thereby improving catalytic performance;

(3) The preparation of electrode materials by electrochemical deposition technology controllably builds nanostructures on the substrate, which is conducive to enhancing the adhesion between platinum nanoclusters and self-supporting nitrogen-doped carbon nanotubes, and effectively solving the problem of platinum metal units. The structure is seriously agglomerated, thereby improving its electrochemical performance.

Description of drawings

Fig. 1 is the microscopic morphology of the nitrogen-doped carbon nanotube supported platinum catalyst prepared in Example 1 under a scanning electron microscope (SEM);

Fig. 2 is the linear sweep voltammetry test pattern (LSV) of the oxygen reduction reaction (ORR) of the nitrogen-doped carbon nanotube supported platinum catalyst prepared in Examples 1, 2, 3, comparative example 1 and commercial catalysts under alkaline conditions ;

Fig. 3 is the linear sweep voltammetry test pattern (LSV) of the methanol oxidation reaction (MOR) of the nitrogen-doped carbon nanotube supported platinum catalyst prepared in Examples 1, 2, 3, comparative example 1 and commercial catalysts under alkaline conditions .

Detailed ways

In order to make the purpose, technical scheme and beneficial technical effect of the present invention clearer, the preparation method of a nickel-cobalt-selenide-supported platinum catalyst of the present invention and its dual-functional catalytic effect will be described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the embodiments described in this specification are only for explaining the present invention, not limiting the present invention, and the parameters and proportions of the embodiments can be selected according to local conditions and have no substantial influence on the results.

Example 1

A kind of preparation of bifunctional nickel cobalt selenide supported platinum catalyst specifically comprises the following steps:

(1) Synthesis of cobalt-iron nanowires:

Take a carbon cloth with a size of 3cm×4cm and sonicate it in 10wt.% potassium permanganate solution for 10min, continue sonicating in deionized water and ethanol until the solution is completely clear, and dry it in a vacuum oven at 60°C for 12h. Add 388mg of cobalt nitrate hexahydrate, 270mg of ferric nitrate nonahydrate, 186mg of ammonium fluoride, and 600mg of urea into 40ml of deionized water, stir for 10 minutes to form a uniform mixed solution, transfer it to a hydrothermal reaction kettle, and immerse the carbon cloth in it. Stand at 120°C for 6h. Then, the carbon cloth was taken out, washed with deionized water and ethanol in turn, and finally dried in a vacuum oven at 40 °C for 12 h.

(2) Synthesis of nitrogen-doped carbon nanotubes:

The carbon cloth for growing cobalt-iron nanowires and 1.5 g of dicyandiamide were placed in two different porcelain boats of a tube furnace, and the dicyandiamide was located upstream of the tube furnace, annealed at 400 °C in an Ar gas atmosphere 1h, the temperature is raised to 700°C and annealing is continued for 1.5h, and the heating rate is 5°C/min. The obtained sample is denoted as CoFe@NCNT/CC.

(3) Synthesis of nitrogen-doped carbon nanotube-supported nickel-cobalt hydroxide:

Take 1cm×4cm of nitrogen-doped carbon nanotubes and arrange them in a mixed solution of 1.8g cobalt chloride hexahydrate, 0.9g nickel chloride hexahydrate, 1.5g urea and 70mL deionized water, and stir for 30min to form a uniform mixed solution , transferred to a hydrothermal reactor, reacted at 120°C for 6h, took out the carbon cloth, washed it with deionized water and ethanol, and finally dried it in a vacuum oven at 60°C for 24h.

(4) Synthesis of nitrogen-doped carbon nanotube-supported nickel-cobalt selenide:

Place 1cm×4cm carbon cloth with nickel-cobalt nanosheets and 1g selenium powder in two different porcelain boats in a tube furnace. The selenium powder is located upstream of the tube furnace, and annealed at 400°C for 2h in an Ar gas atmosphere , the heating rate is 5°C/min. The obtained samples are denoted as NiCoS _x @CoFe@NCNT@CC.

(5) Synthesis of nickel-cobalt-selenide supported platinum catalyst:

The carbon cloth loaded with nickel-cobalt-selenide is used as the cathode, the platinum sheet is used as the anode, and the saturated calomel electrode is used as the reference electrode, and placed in 5 mmol/L chloroplatinic acid and 50 mmol/L potassium dihydrogen phosphate solution for constant voltage deposition for 5000s , the carbon cloth was taken out, washed with deionized water and ethanol, and finally dried in a vacuum oven at 60 °C for 6 h. The obtained sample is denoted as 1-Pt@NiCoS _x @CoFe@NCNT@CC.

The morphology of the 1-Pt@NiCoS _x @CoFe@NCNT@CC material obtained in Example 1 was analyzed by scanning electron microscopy (SEM). The results are shown in Figure 1. Platinum nanoclusters are loaded on NiCoS _x @CoFe @NCNT @CC surface.

Example 2

A kind of preparation of bifunctional nickel cobalt selenide supported platinum catalyst specifically comprises the following steps:

(1) This step is the same as step (1) in Example 1:

(2) This step is the same as step (2) in Example 1:

(3) This step is identical with step (3) in embodiment 1:

(4) Synthesis of nitrogen-doped carbon nanotube-supported nickel-cobalt selenide:

Place 1cm×4cm carbon cloth with nickel-cobalt nanosheets and 2.0g selenium powder in two different porcelain boats in a tube furnace. The selenium powder is located upstream of the tube furnace and annealed at 400°C in an Ar gas atmosphere 2h, the heating rate is 5°C/min.

(5) Synthesis of nickel-cobalt-selenide supported platinum catalyst:

The carbon cloth loaded with nickel-cobalt-selenide is used as the cathode, the platinum sheet is used as the anode, and the saturated calomel electrode is used as the reference electrode, and placed in 5 mmol/L chloroplatinic acid and 60 mmol/L potassium dihydrogen phosphate solution for constant voltage deposition for 5000s , the carbon cloth was taken out, washed with deionized water and ethanol, and finally dried in a vacuum oven at 60 °C for 6 h. The obtained sample is denoted as 2-Pt@NiCoS _x @CoFe@NCNT@CC.

Example 3:

(1) This step is the same as step (1) in Example 1:

(2) This step is the same as step (2) in Example 1:

(3) This step is identical with step (3) in embodiment 1:

(4) This step is identical with step (4) in embodiment 1:

(5) Synthesis of nickel-cobalt-selenide supported platinum catalyst:

The carbon cloth loaded with nickel-cobalt-selenide is used as the cathode, the platinum sheet is used as the anode, and the saturated calomel electrode is used as the reference electrode, and placed in 10mmol/L chloroplatinic acid and 50mmol/L potassium dihydrogen phosphate solution for constant voltage deposition for 5000s , the carbon cloth was taken out, washed with deionized water and ethanol, and finally dried in a vacuum oven at 60 °C for 6 h. The obtained sample is denoted as 3-Pt@NiCoS _x @CoFe@NCNT@CC.

Comparative example 1

A preparation method for nitrogen-doped carbon nanotube-supported platinum, specifically comprising the following steps:

(1) This step is the same as step (1) in Example 1:

(2) This step is the same as step (2) in Example 1. :

(3) Synthesis of nitrogen-doped carbon nanotube-supported platinum:

With 1cm×1cm nitrogen-doped carbon nanotube carbon cloth as cathode, platinum sheet as anode, and saturated calomel electrode as reference electrode, place in 5mmol/L chloroplatinic acid and 50mmol/L potassium dihydrogen phosphate solution After constant pressure deposition for 5000s, the carbon cloth was taken out, washed with deionized water and ethanol, and finally dried in a vacuum oven at 60°C for 6h. The obtained samples are denoted as Pt@CoFe@NCNT@CC.

Bifunctional Catalytic Performance Evaluation

The electrochemical workstation model used for all electrochemical tests is CHI 760E and is equipped with a PINE rotating disc electrode test system, and the electrochemical tests are performed at room temperature.

Preparation of the working electrode: Before using the rotating disk electrode (RDE), that is, the glassy carbon electrode (GCE, d=0.5cm), the electrode surface is first polished to a mirror surface on a polishing cloth with Al ₂ O ₃ powder, and then rinsed with distilled water Several times, and ultrasonic vibration for 10s, room temperature and dry before use. A sample with a diameter of 5 mm was cut from the prepared sample with a puncher, and 5-10 μL of Nafion solution (5 wt.%) was taken to stick the carbon cloth to the surface of the GCE, and dried naturally to obtain the working electrode for the test. The loading amount of platinum in the catalyst on the electrode surface is about 0.5 mg cm ^-2 . Comparative examples were prepared and tested using the same electrode preparation method.

Electrochemical performance test: A standard three-electrode electrochemical test system was used during the test, wherein the counter electrode was a Pt sheet, the reference electrode was a saturated calomel electrode (SCE) and the working electrode prepared above.

The LSV curves of 1-Pt@NiCoS _x @CoFe@NCNT@CC samples and commercial 20wt.%Pt/C catalysts in _1M KOH electrolyte saturated with O2 at 1600rpm were tested by rotating disk electrode (RDE), respectively, The result is shown in Figure 2. The 1-Pt@NiCoS _x @CoFe@NCNT@CC sample exhibited high ORR electrocatalytic activity (in 1M KOH, the onset potential and half-wave potential were 0.95 and 0.87 V vs. RHE), and its electrocatalytic activity surpassed the commercial Pt/C catalyst tested under the same conditions (in 1M KOH, the onset potential and half-wave potential were 1.16 and 0.79V vs. RHE), notably the limiting current density of the sample (23.51mA/cm ² ) is much higher than that of commercial Pt/C (16.92mA/cm ² ), and the half-wave potential of the self-supporting electrode is more positive than that of Pt/C, indicating that this material has faster reaction kinetics in ORR electrocatalysis.

MOR catalysis of 1-Pt@NiCoS _x @CoFe@NCNT@CC samples and commercial 20 wt.% Pt/C catalysts in N ₂ saturated 1M KOH and 1M CH ₃ OH mixed electrolyte was tested by rotating disk electrode (RDE) active. Figure 3 shows the LSV curve of the MOR catalytic performance of the 1-Pt@NiCoS _x @CoFe@NCNT@CC sample. When scanning forward, the maximum current density j _f value of 1-Pt@NiCoS _x @CoFe@NCNT@CC is about 59.42mA cm ^-2 , while that of Pt/C is about 47.27mAcm ^-2 _. The j _f of 1-Pt@NiCoS _x @CoFe@NCNT@CC and Pt/C are about 8.64mA cm ^-2 and 3.37mA cm ^-2 when reverse scanning. Under the same test conditions, the peak current density of the 1-Pt@NiCoS _x @CoFe@NCNT@CC sample is the largest, indicating that the 1-Pt@NiCoS _x @CoFe@NCNT@CC sample has excellent MOR electrocatalytic activity.

It should also be noted that at last: the above embodiments are only in order to illustrate the technical scheme of the present invention, rather than limit it; Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: It is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the various embodiments of the present invention. range.

Claims (7)

1. The preparation method of the difunctional nickel cobalt selenide supported platinum catalyst is characterized in that carbon cloth is used as a carrier, nitrogen doped carbon nanotubes (NCNTs) are used as a conductive network, nickel cobalt selenide is used as a deposition site, and an electrodeposition method is adopted to load platinum nanoclusters on the nickel cobalt selenide.

2. The preparation method according to claim 1, characterized in that it comprises the following steps:

(1) And (3) synthesis of cobalt-iron nanowires: preparing cobalt-iron nanowires by using carbon cloth as a precursor and cobalt nitrate hexahydrate, ferric nitrate nonahydrate, ammonium fluoride and urea;

(2) Synthesis of nitrogen doped carbon nanotubes: preparing a nitrogen-doped carbon nano tube from carbon cloth and dicyandiamide for growing cobalt-iron nanowires;

(3) Synthesizing the nitrogen-doped carbon nano tube loaded nickel cobalt hydroxide: preparing nickel-cobalt nano-sheets from cobalt chloride hexahydrate, nickel chloride hexahydrate and urea by taking carbon cloth for growing nitrogen-doped carbon nano-tubes as a precursor;

(4) Synthesizing the nitrogen-doped carbon nano tube loaded nickel cobalt selenide: preparing nickel cobalt selenide from carbon cloth growing nickel cobalt nanosheets and selenium powder;

(5) Synthesis of a nickel cobalt selenide supported platinum catalyst: and growing the platinum nanocluster on the surface of the carbon cloth of the nickel cobalt selenide-loaded carbon nanotube by adopting an electrodeposition method.

3. The preparation method of claim 2, wherein the specific synthesis process of the cobalt-iron nanowire in the step (1) is as follows: ultrasonic treatment is carried out on carbon cloth with certain size in 8-12 wt% potassium permanganate solution for 15-30min, ultrasonic treatment is carried out on deionized water and ethanol until the solution is completely clear, drying is carried out for 4-6 h at 50-80 ℃, carbon is arranged in mixed solution of 0.2-0.4 g cobalt nitrate hexahydrate, 0.2-0.3 g ferric nitrate nonahydrate, 0.1-0.3 g ammonium fluoride, 0.5-1.0 g urea and 40-50 mL deionized water, uniform mixed solution is formed by stirring, the mixed solution is transferred into a hydrothermal reaction kettle, reaction is carried out for 6-8 h at 125-135 ℃, the carbon cloth is taken out, washing is carried out by deionized water and ethanol, and finally drying is carried out in a vacuum oven at 50-60 ℃ for 4-6 h.

4. The method of claim 2, wherein the synthesis of the nitrogen-doped carbon nanotubes in step (2) comprises the following steps: placing carbon cloth for growing the ferrocobalt nanowires and dicyandiamide in two different porcelain boats of a tube furnace, wherein the dicyandiamide is positioned at the upstream of the tube furnace, annealing for 2-4 h at 400 ℃ in an inert gas atmosphere, continuously heating to 700-800 ℃ and annealing for 2h, and the heating rate is 3-5 ℃/min.

5. The preparation method of claim 2, wherein the specific synthesis process of the nitrogen-doped carbon nanotube-supported nickel cobalt hydroxide in the step (3) is as follows: arranging carbon for growing nitrogen doped carbon nano tubes in a mixed solution of cobalt chloride hexahydrate, nickel chloride hexahydrate, urea and deionized water, stirring for 20-40 min to form a uniform mixed solution, transferring the uniform mixed solution into a hydrothermal reaction kettle, reacting for 6-8 h at 110-125 ℃, taking out carbon cloth, washing with deionized water and ethanol, and finally drying in a vacuum oven at 50-60 ℃ for 6-8 h.

6. The preparation method of claim 2, wherein the specific synthesis process of the nitrogen-doped carbon nanotube-supported nickel cobalt selenide in the step (4) is as follows: placing carbon cloth growing nickel cobalt nano-sheets and 0.5-2.0 g of selenium powder into two different porcelain boats of a tube furnace, wherein the selenium powder is positioned at the upstream of the tube furnace, heating to 400-800 ℃ in an inert gas atmosphere, and annealing for 2-4 h, wherein the heating rate is 3-5 ℃/min.

7. The preparation method of claim 2, wherein the synthesis of the nickel cobalt selenide supported platinum catalyst in the step (5) comprises the following specific steps: the carbon cloth loaded with nickel cobalt selenide is used as a cathode, a platinum sheet is used as an anode, a saturated calomel electrode is used as a reference electrode, the carbon cloth is placed in 1-10 mmol/L chloroplatinic acid and 50-60 mmol/L monopotassium phosphate solution to deposit for 1000-5000 s at constant pressure, the carbon cloth is taken out, washed with deionized water and ethanol, and finally dried in a vacuum oven at 40-60 ℃ for 6-24 h.

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