Method for preparing platinum-carbon catalyst of fuel cell

Abstract

The invention discloses a method for preparing a fuel cell platinum-carbon catalyst, and relates to the technical field of fuel cells, and the method comprises the following steps: (1) mixing: fully mixing an alkali solution, a chloroplatinic acid solution and carbon carrier slurry according to a mass ratio, and uniformly dispersing to obtain platinum-carbon precursor slurry; (2) reaction: transferring the platinum-carbon precursor slurry into a reaction device, and carrying out first-step reaction; (3) secondary reaction: heating the cooled solution to 110-130 DEG C, carrying out secondary reaction for 10-30 minutes, ending the reaction, stopping heating, and cooling the reaction solution to 50-70 DEG C; and (4) adjusting the pH of the system. (5) cleaning and filtering: cleaning and filtering for 5-10 times by using ultrapure water to obtain a wet catalyst; and (6) drying: transferring the wet platinum-carbon catalyst into a vacuum drying box at 70-90 DEG C, and carrying out vacuum drying for 8-12 hours.

Description

Technical Field

[0001] The invention relates to the technical field of fuel cells, and in particular to a method for preparing a platinum-carbon catalyst for a fuel cell. Background Art

[0002] The improvement of fuel cell performance is mainly limited by the oxygen reduction reaction on the cathode side. In order to improve the performance of fuel cells, it is necessary to increase the amount of precious metal catalysts on the cathode side. Since platinum metal is expensive, improving catalyst performance has become the key.

[0003] The higher the platinum content in the platinum-carbon catalyst, the smaller the platinum particles, the higher the dispersibility, the less nano-stacking between the platinum particles, the higher the surface atomic utilization rate, and the better the catalyst performance. The polyol reduction method is now widely used in the preparation of platinum-carbon catalysts for fuel cells. It uses ethylene glycol aqueous solution as a solvent, disperses the precursor compound in the solvent, controls the solution pH and reduction temperature, and reduces the platinum salt to platinum nanoparticles under microwave or oil bath heating conditions. The method of loading on the surface of a uniformly dispersed carbon carrier causes chloroplatinic acid to react incompletely in the ethylene glycol aqueous solution, and the platinum loading is low. Therefore, it is urgent to design a method for preparing fuel cell platinum-carbon catalysts to solve the above problems. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing a platinum-carbon catalyst for a fuel cell, so as to solve the defects of the existing catalyst using ethylene glycol aqueous solution as solvent proposed in the above background technology, which causes incomplete reaction of chloroplatinic acid in ethylene glycol aqueous solution and low platinum loading.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for preparing a platinum-carbon catalyst for a fuel cell, comprising the following steps:

[0006] (1) Mixing: fully mix the alkaline solution, chloroplatinic acid solution and carbon carrier slurry in a mass ratio of 0.5-1:8-11:9-12, and disperse them evenly to obtain a platinum-carbon precursor slurry;

[0007] (2) Reaction: Transfer the platinum-carbon precursor slurry to a reaction device, heat it to 110-130° C., carry out the first step reaction, react for 20-60 min, terminate the reaction, stop heating, and wait for the reaction solution to cool to 50-70° C.;

[0008] (3) Secondary reaction: The solution after cooling is heated to 110-130° C., and a secondary reaction is carried out for 10-30 minutes. The reaction is terminated, and heating is stopped. The reaction solution is cooled to 50-70° C.;

[0009] (4) Adjusting the pH of the system: adding a strong acid to the above solution to adjust the pH of the solution to <5, thereby obtaining a mixed solution of the platinum-carbon catalyst and alcohol.

[0010] (5) Washing and filtering: Transfer the above mixed solution to a filter, and wash and filter it with ultrapure water 5 - 10 times to obtain a wet catalyst;

[0011] (6) Drying: Transfer the wet platinum-carbon catalyst to a vacuum drying oven at 70 - 90 °C and dry it under vacuum for 8 - 12 hours.

[0012] Preferably, the alkaline solution in step (1) is one of sodium bicarbonate, potassium hydroxide, sodium hydroxide, and calcium hydroxide solutions, with a mass fraction of 5 - 15%.

[0013] Preferably, the carbon support slurry in step (1) is a mixture of one or more of carbon black, carbon nanotubes, mesoporous carbon, carbon nanofibers, and graphene with one or more solutions of water, ethanol, isopropanol, n-propanol, ethylene glycol, and glycerol, and the mass fraction of the carbon support is 0.3 - 1.0%.

[0014] Preferably, in the chloroplatinic acid solution in step (1), the mass fraction of chloroplatinic acid is 1 - 2%.

[0015] Preferably, the dispersion method in step (2) is one or more of ultrasonic, shearing, and ball milling.

[0016] Preferably, the strong acid in step (4) is one or more of nitric acid, sulfuric acid, and hydrochloric acid.

[0017] Preferably, the filter in step (5) is one of a positive pressure filter or a negative pressure filter.

[0018] Preferably, the platinum loading of the catalyst obtained in step (6) is 20 - 80%.

[0019] Compared with the prior art, the beneficial effects of the present invention are: The platinum-carbon catalyst prepared by the method for preparing the fuel cell platinum-carbon catalyst has a relatively accurate loading. Compared with the general reduction method, it can make the chloroplatinic acid react completely in the ethylene glycol aqueous solution and has a relatively high platinum loading. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the reaction flow chart of the present invention;

[0021] Figure 2 is the comparison chart of Comparative Example 2 and Example 1 of the present invention;

[0022] Figure 3 is the comparison chart of Comparative Example 2 and Example 1 of the present invention;

[0023] Figure 4 is the comparison chart of Comparative Example 1 and Example 1 of the present invention;

[0024] Figure 5This is a comparison chart between Comparative Example 2 and Example 1 of the present invention. Detailed implementation mode

[0025] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0026] Consult Figures 1-5 , an embodiment provided by the present invention: a method for preparing a fuel cell platinum-carbon catalyst, comprising the following steps:

[0027] (1) Mixing: Mix an alkali solution, a chloroplatinic acid solution, and a carbon support slurry in a mass ratio of 0.5-1:8-11:9-12, and disperse evenly to obtain a platinum-carbon precursor slurry;

[0028] (2) Reaction: Transfer the platinum-carbon precursor slurry to a reaction device, heat it to 110-130 °C, carry out the first reaction for 20-60 minutes, end the reaction, stop heating, and wait for the reaction solution to cool to 50-70 °C;

[0029] (3) Secondary reaction: Heat the above-cooled solution to 110-130 °C, carry out a secondary reaction for 10-30 minutes, end the reaction, stop heating, and wait for the reaction solution to cool to 50-70 °C;

[0030] (4) Adjust the pH of the system: Add a strong acid to the above solution to adjust the pH of the solution <5 to obtain a mixed solution of a platinum-carbon catalyst and an alcohol.

[0031] (5) Cleaning and filtering: Transfer the above mixed solution to a filter, wash and filter it with ultrapure water 5-10 times to obtain a wet catalyst;

[0032] (6) Drying: Transfer the wet platinum-carbon catalyst to a vacuum drying oven at 70-90 °C and vacuum dry it for 8-12 hours.

[0033] Furthermore, the alkali solution in step (1) is one of sodium bicarbonate, potassium hydroxide, sodium hydroxide, and calcium hydroxide solutions, and the mass fraction is 5-15%.

[0034] Furthermore, the carbon support slurry in step (1) is a mixture of one or more of carbon black, carbon nanotubes, mesoporous carbon, carbon nanofibers, and graphene and one or more solutions of water, ethanol, isopropanol, n-propanol, ethylene glycol, and glycerol, and the mass fraction of the carbon support is 0.3-1.0%.

[0035] Further, in the chloroplatinic acid solution in step (1), the mass fraction of chloroplatinic acid is 1-2%.

[0036] Further, the dispersion method in step (2) is one or more of ultrasonic, shearing, and ball milling.

[0037] Further, the strong acid in step (4) is one or more of nitric acid, sulfuric acid, and hydrochloric acid.

[0038] Further, the filter in step (5) is one of a positive pressure filter or a negative pressure filter.

[0039] Further, the platinum loading of the catalyst obtained in step (6) is 20-80%.

[0040] Example 1: Use a shearing device to uniformly mix 85 g of a chloroplatinic acid solution containing 0.6 g of platinum and 0.4 g of a conductive carbon black slurry, and gradually add 10 g of a potassium hydroxide solution with a mass fraction of 10%. Stir for 90 min. Transfer the mixed solution to a microwave chemical reaction device, heat it to 120 °C and keep it warm for 3 min to complete the first-step reaction. Cool the solution to 60 ± 2 °C, and then microwave heat it to 120 °C again and keep it warm for 1 min to end the second-step reaction. After the reaction solution is cooled to room temperature, add 1.5 ml of concentrated hydrochloric acid and adjust the pH to ≤ 3.

[0041] Transfer the mixed solution of the above catalyst and alcohol to a positive pressure filter, use a PTFE microporous membrane, add 800 ml of ultrapure water, and start filtering by pressurizing to 0.2 MPa. Repeat steps 8-10 times, measure the conductivity of the filtrate < 3 μS / cm to obtain a wet platinum-carbon catalyst, and place the catalyst in a vacuum drying oven at 80 °C for drying for 10 hours to obtain 1 g of a dry platinum-carbon catalyst with a platinum content of 60%.

[0042] Example 2: Ultrasonically mix 0.6 g of a boron-doped carbon nanotube ethylene glycol slurry uniformly, add 60 g of a chloroplatinic acid solution containing 0.4 g of platinum, and then gradually add 6 g of a sodium hydroxide aqueous solution with a mass fraction of 10%. The mass ratio of ethylene glycol to water is 2:1, and stir for 120 min. Transfer the mixed solution to an oil bath reaction device, heat it to 110 °C and keep it warm for 30 min to complete the first-step reaction. Cool the solution to 70 ± 5 °C, and then oil bath heat it to 118 °C again and keep it warm for 10 min to end the second-step reaction. After the reaction solution is cooled to room temperature, add 1 ml of concentrated hydrochloric acid and adjust the pH to ≤ 3.

[0043] Transfer the above catalyst mixed solution to a positive pressure filter, use a PTFE microporous filter membrane, add 800 ml of ultrapure water, pressurize to 0.2 MPa and start filtering. Repeat steps 8 - 10 times, measure the conductivity of the filtrate < 3 μS / cm to obtain a wet platinum-carbon catalyst, and place the catalyst in a vacuum drying oven at 80 °C for drying for 8 hours to obtain 1 g of dry platinum-carbon catalyst with a platinum content of 40%.

[0044] Example 3: Ultrasonically mix 5 g of nitrogen-doped graphene ethylene glycol slurry evenly, and then gradually add 80 g of a sodium hydroxide solution with a mass fraction of 10% dropwise to 700 g of a chloroplatinic acid solution containing 4 g of platinum. The mass ratio of ethylene glycol to propylene glycol is 2:1. Shear and disperse for 40 min and stir for 90 min. Transfer the mixed solution to an oil bath reaction device, heat to 125 °C and keep warm for 40 min to complete the first-step reaction. Cool the solution to 80 ± 5 °C, and then heat it in an oil bath to 130 °C again and keep warm for 20 min to end the second-step reaction. After the reaction solution is cooled to room temperature, add 12 ml of concentrated hydrochloric acid dropwise while stirring to adjust the pH to ≤ 2.5.

[0045] Transfer the above catalyst mixed solution to a positive pressure filter, use the PTFE microporous filter membrane, add 1000 ml of ultrapure water, pressurize to 0.3 MPa and start filtering. When 800 ml of filtrate is filtered out, open the air release valve to relieve pressure, re-add 800 ml of ultrapure water and pressurize to 0.3 MPa to start filtering. Repeat steps 10 - 15 times, measure the conductivity of the filtrate < 3.5 μS / cm to obtain a wet platinum-carbon catalyst, and place the catalyst in a vacuum drying oven at 85 °C for drying for 12 hours to obtain 10 g of dry platinum-carbon catalyst with a platinum content of 50%.

[0046] Example 4: Ultrasonically disperse 7 g of mesoporous carbon in an aqueous propylene glycol solution. After uniform dispersion, add 714 g of a chloroplatinic acid alcohol solution containing 14 g of platinum and 120 g of an aqueous sodium hydroxide solution with a mass fraction of 12%. The mass ratio of propylene glycol to water is 3:1. Shear and disperse for 40 min, transfer the mixed solution to a reaction kettle, and stir for 120 min. Heat the reaction solution to 115 °C and keep warm for 60 min to complete the first-step reaction. Cool the solution to 80 ± 5 °C, and then heat it in an oil bath to 125 °C again and keep warm for 20 min to end the second-step reaction. After the reaction solution is cooled to room temperature, add 20 ml of concentrated hydrochloric acid dropwise while stirring to adjust the pH to ≤ 2.3.

[0047] Let the above catalyst mixed solution stand for layering, pour out the upper clear liquid, transfer the remaining solution to a positive pressure filter, use a PTFE microporous filter membrane, add ultrapure water twice the volume of the remaining solution, and start filtering when the pressure is increased to 0.3 MPa. The air release valve can be opened to relieve pressure when the liquid in the filter remains about 300 ml. Then add 800 ml of ultrapure water and start filtering when the pressure is increased to 0.3 MPa. Repeat steps 8 - 12 times, measure the conductivity of the filtrate < 3.8 μS / cm to obtain a wet platinum-carbon catalyst, and place the catalyst in a vacuum drying oven to dry at 85 °C for 15 hours to obtain 20 g of a dry platinum-carbon catalyst with a platinum content of 70%.

[0048] Comparative Example 1: JM Johnson Matthey Hispec9100 catalyst, 60% platinum-carbon catalyst

[0049] Compare the catalyst performances of Example 1 and Comparative Example 1, see Figure 4 , after 20 cycles of activation in 0.1 M perchloric acid solution, the electrochemically active surface area (ECSA) of the platinum-carbon catalyst PT60 prepared in Example 1 of the present invention is 80.5 m2 / g, and that of the JM catalyst in Comparative Example 1 is 45.19 m2 / g, indicating that the prepared platinum-carbon catalyst has good performance and platinum is evenly dispersed on the surface of the carbon support; under oxygen saturation, the sweep rate is 10 mV / s, the scanning voltage is -0.2 - 0.7 (versus saturated calomel electrode SCE), and the rotation speed is 1600 rpm. The mass activity of the platinum-carbon catalyst PT60 prepared in Example 1 of the present invention is measured to be 142 mA / mg@0.599 V (vs. SCE), indicating that the platinum-carbon catalyst PT60 has high oxygen reduction catalytic activity, while the JM catalyst in Comparative Example 1 is only 94.1

[0050] mA / mg@0.599 V (vs. SCE).

[0051] Comparative Example 2: Self-made 60% platinum-carbon catalyst of a single microwave reaction sample

[0052] Compare the catalyst performances of Example 1 and Comparative Example 2, see Figure 2 、 Figure 3 and Figure 5, after 20 cycles of activation in 0.1 M perchloric acid solution, the electrochemically active surface area (ECSA) of the platinum-carbon catalyst PT60 prepared in Example 1 of the present invention is 80.5 m2 / g, and that of the 60% platinum-carbon catalyst in Comparative Example 2 is 57.4 m2 / g, indicating that the prepared platinum-carbon catalyst has good performance and platinum is evenly dispersed on the surface of the carbon support; under oxygen saturation, with a scan rate of 10 mV / s, a scanning voltage of -0.2 - 0.7 (vs. saturated calomel electrode SCE), and a rotation speed of 1600 rpm, the mass activity of the platinum-carbon catalyst PT60 prepared in Example 1 of the present invention is measured to be 142 mA / mg@0.599 V (vs. SCE), indicating that the platinum-carbon catalyst PT60 has high oxygen reduction catalytic activity, while the 60% platinum-carbon catalyst in Comparative Example 2 is only 80 mA / mg@0.599 V (vs. SCE).

[0053] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

Claims

1. A method for preparing a platinum-carbon catalyst for a fuel cell, characterized in that, The preparation method comprises the following steps: (1) Mixing: fully mix the alkaline solution, chloroplatinic acid solution and carbon carrier slurry in a mass ratio of 0.5-1:8-11:9-12, and disperse them evenly to obtain a platinum-carbon precursor slurry; (2) Reaction: Transfer the platinum-carbon precursor slurry to a reaction device, heat it to 110-130° C., carry out the first step reaction, react for 20-60 min, terminate the reaction, stop heating, and wait for the reaction solution to cool to 50-70° C.; (3) Secondary reaction: The solution after cooling is heated to 110-130° C., and a secondary reaction is carried out for 10-30 minutes. The reaction is terminated, and heating is stopped. The reaction solution is cooled to 50-70° C.; (4) Adjusting the pH of the system: adding a strong acid to the above solution to adjust the pH of the solution to <5, thereby obtaining a mixed solution of the platinum-carbon catalyst and alcohol. (5) Cleaning and filtration: The mixed solution is transferred to a filter and cleaned and filtered with ultrapure water for 5-10 times to obtain a wet catalyst; (6) Drying: The wet platinum-carbon catalyst was transferred to a vacuum drying oven at 70-90°C and vacuum dried for 8-12 hours.

2. The method for preparing a fuel cell platinum-carbon catalyst according to claim 1, characterized in that, The alkaline solution in step (1) is one of sodium bicarbonate, potassium hydroxide, sodium hydroxide and calcium hydroxide solution, with a mass fraction of 5-15%.

3. The method for preparing the fuel cell platinum-carbon catalyst according to claim 1, wherein The carbon carrier slurry in step (1) is a mixture of one or more of carbon black, carbon nanotubes, mesoporous carbon, carbon nanofibers, and graphene with one or more solutions of water, ethanol, isopropanol, n-propanol, ethylene glycol, and glycerol, and the mass fraction of the carbon carrier is 0.3-1.0%.

4. The method for preparing the fuel cell platinum-carbon catalyst according to claim 1, characterized in that, In the chloroplatinic acid solution in step (1), the mass fraction of chloroplatinic acid is 1-2%.

5. The method for preparing a fuel cell platinum-carbon catalyst according to claim 1, wherein The dispersion method in step (2) is one or more of ultrasound, shearing, and ball milling.

6. The method for preparing the fuel cell platinum-carbon catalyst according to claim 1, characterized in that, The strong acid in step (4) is one or more of nitric acid, sulfuric acid and hydrochloric acid.

7. The method for preparing a fuel cell platinum-carbon catalyst according to claim 1, wherein The filter in step (5) is a positive pressure filter or a negative pressure filter.

8. The method for preparing the fuel cell platinum-carbon catalyst according to claim 1, wherein, The platinum loading of the catalyst obtained in step (6) is 20-80%.

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