A method for preparing a carbon support for a catalyst with small and ordered particles

Abstract

The present application belongs to the technical field of fuel cell catalysts, and specifically discloses a carbon carrier preparation method for synthesizing a catalyst with small and ordered particles, which comprises the following steps: dispersing the carbon carrier into a nitric acid solution, stirring until uniform, performing suction filtration and drying treatment on the obtained carbon carrier nitric acid solution; grinding the obtained carbon carrier, adding sodium mercaptoacetate and water for impregnation, stirring until uniform after ultrasonic dispersion; drying and grinding the obtained solution, and performing annealing in an inert atmosphere to obtain a carbon carrier for catalyst preparation. The metal catalyst metal content on the carbon carrier prepared by the present application can reach 30%-50%, and the catalytic performance is excellent; the preparation method is simple, and is suitable for mass production of metal catalysts.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of fuel cell catalysts, and particularly relates to a carbon carrier preparation method for synthesizing a catalyst with small particles and order. BACKGROUND

[0002] A fuel cell is a device that can convert chemical energy stored in oxygen and fuel into electrical energy in an electrochemical reaction, and has the characteristics of high energy density, high energy conversion efficiency and environmental friendliness, and thus is a new generation of clean energy technology and is highly concerned. However, the industrialization process of fuel cells still has many obstacles, and the biggest obstacle is the slow oxygen reduction reaction of the cathode. Compared with the fuel oxidation reaction of the anode, the kinetic rate is nearly 2 to 3 orders of magnitude slower, which requires a large amount of efficient catalyst to reduce the overpotential and improve the output voltage of the entire fuel cell.

[0003] Catalyst as the core material of fuel cell stack, its comprehensive performance is directly related to the core competitiveness of fuel cell technology and its industrialization prospects. Because Pt has good molecular adsorption and dissociation characteristics, carbon-supported platinum-based catalyst is considered to be the mainstream cathode catalyst for fuel cells and metal-air batteries. Considering the gas, water and electron transmission phenomena existing in fuel cells and metal-air batteries, the higher the metal content of the catalyst, the thinner the membrane electrode, and the shorter the transmission distance, which is beneficial to the improvement of the performance of the battery. However, with the increase of the metal content, the conventional catalytic preparation process is often accompanied by problems such as catalyst agglomeration and sintering, which seriously affects the ORR (oxygen reduction reaction) performance of the catalyst, which also hinders the development of fuel cells and metal-air battery technology. At the same time, the working conditions of fuel cells are complex, and the stability of the catalyst is also a severe test. During the preparation process of the catalyst, the interaction between the carrier and the metal particles is beneficial to adjusting the interface adhesion energy to achieve the purpose of sintering resistance, and high temperature is needed in the preparation process to promote alloying and obtain thermodynamic driving force to synthesize highly ordered intermetallic catalysts such as PtCo / C. Although the ordered intermetallic compound Pt-M alloy catalyst has good catalytic performance, it is still a challenge to synthesize ideal intermetallic compound catalysts. The disorder phase transition in atomic arrangement needs to overcome slow kinetics. The general method is to carry out high-temperature annealing treatment for a long time, for example, at 700 DEG C for 6 hours or more. Therefore, it is always a research hotspot to ensure high loading while ensuring order and not easy to sinter. At present, the common methods are: using MgO shell to protect PtCo nanoparticles to prevent particle agglomeration during high-temperature process; using KCl protective matrix to inhibit the movement of Pt3Fe particles; using SiO2 coating to prepare ordered PtFeIr intermetallic compound nanowires with an average diameter of 2.6 nm. The latest strategy is to anchor small particles by strengthening the catalyst-carrier interaction, inhibit the direct contact of particles, and adjust the Pt-S catalyst-carrier interaction to prevent particle migration during annealing process. However, whether it is spatial isolation or adjustment of metal-carrier interaction, it is difficult to avoid high annealing temperature and / or long holding time, so it is inevitable that the particles grow up and the catalyst activity decreases, and the subsequent processing technology is complex. SUMMARY

[0004] The purpose of the present application is to overcome the defects existing in the prior art, and to provide a carbon carrier preparation method for synthesizing small and ordered catalyst particles, which solves the problems of high annealing temperature and / or long holding time and complex subsequent processing technology by directly starting from the carbon carrier.

[0005] In order to achieve the above purpose, one of the technical solutions of the present application is: a carbon carrier preparation method for synthesizing small and ordered catalyst particles, which specifically comprises the following steps:

[0006] (1) Disperse the carbon support in the nitric acid solution and stir until homogeneous;

[0007] (2) The carbon support nitric acid solution obtained in step (1) is subjected to vacuum filtration and drying.

[0008] (3) Grind the carbon support obtained in step (2), then add a certain amount of sodium mercaptoacetate and water (the amount added should just cover the catalyst) to impregnate it, and then disperse it by ultrasonication and stir it evenly.

[0009] (4) The solution obtained in step (3) is dried, ground and then annealed in an inert atmosphere to obtain a carbon support for preparing the catalyst.

[0010] In a preferred embodiment of the present invention, the stirring time in step (1) is 3-7 hours and the rotation speed is 300-500 r / min.

[0011] In a preferred embodiment of the present invention, the carbon support in step (1) is carbon black.

[0012] Optionally, the carbon carrier is either Vulcan XC-72 or Ketjen carbon black. Vulcan XC-72 is a conductive carbon black produced by Cabot Corporation of the United States, and Ketjen is a conductive carbon black produced by Lion Corporation of Japan.

[0013] In a preferred embodiment of the present invention, the concentration of the nitric acid solution in step (1) is 0.8-1.2M, and the amount of carbon support added to the nitric acid solution is 0.03-0.07g / ml.

[0014] In a preferred embodiment of the present invention, the drying method in step (2) is rotary drying.

[0015] In a preferred embodiment of the present invention, the mass ratio of carbon support to sodium mercaptoacetate in step (3) is (2-3):1.

[0016] In a preferred embodiment of the present invention, the grinding time in step (3) is 10-30 min.

[0017] In a preferred embodiment of the present invention, the ultrasonic dispersion time in step (3) is 30-60 min, the stirring time is 2-4 h, and the rotation speed is 50-70 r / min.

[0018] In a preferred embodiment of the present invention, the inert atmosphere in step (4) is argon or nitrogen.

[0019] In a preferred embodiment of the present invention, the annealing in step (4) is carried out in stages: first, the temperature is raised from room temperature to 650-750℃ at a rate of 5-20℃ / min, and the holding time is 2-3h, and then the temperature is automatically reduced.

[0020] To achieve the above objectives, the second technical solution of the present invention is: a carbon support prepared by a method for synthesizing a carbon support for a catalyst with small and ordered particles.

[0021] To achieve the above objectives, the third technical solution of the present invention is: the application of the above-mentioned carbon support in the synthesis of catalysts with small and ordered particles.

[0022] In a preferred embodiment of the present invention, the carbon support is used for impregnation reduction to prepare a high-metal-content PtCo / C intermetallic compound catalyst.

[0023] Furthermore, the method for preparing high metal content PtCo / C intermetallic compound catalysts by impregnation reduction is the same as the method for preparing carbon supports, except that the commercial carbon support impregnated with sodium mercaptoacetate is replaced with the carbon support prepared in this invention impregnated with an auxiliary precursor and a platinum salt precursor.

[0024] Furthermore, the platinum salt precursor is chloroplatinic acid, the auxiliary agent precursor is a soluble inorganic salt of Co, the molar ratio of the auxiliary agent precursor to the platinum salt precursor is 1-2:1, and the mass ratio of the carbon support, platinum salt precursor, and auxiliary agent precursor is 160-200:60-90:100-140.

[0025] Furthermore, the annealing process used in the impregnation reduction preparation of the high metal content PtCo / C intermetallic compound catalyst is an annealing temperature of 700-800℃, a holding time of 1-3h, followed by cooling to 550-650℃ and holding for another 1-3h.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] 1. The method for preparing the catalyst using a carbon support in this invention is green and simple, and suitable for mass production.

[0028] 2. The catalyst prepared by the carbon support method of this invention has obvious anti-sintering ability, small particle size, average particle size of 3.0-5.4 nm, uniform particle dispersion, no obvious agglomeration, and obvious degree of ordering.

[0029] 3. The catalyst prepared by the carbon support method of this invention has a high metal content of 30%-50%, which is in line with practical applications. Attached Figure Description

[0030] Figure 1The XRD patterns of the PtCo / C electrocatalysts prepared in Example 1 and Comparative Example 1 of this invention are shown (scan range 20-55°, scan rate 10° / min).

[0031] Figure 2 This is a comparison diagram of the particle size of the PtCo / C electrocatalysts prepared in Example 1 and Comparative Example 1 of the present invention;

[0032] Figure 3 A comparison of polarization curves of the PtCo / C electrocatalyst prepared in Example 1 of this invention in 0.1M oxygen-saturated HClO4 solution;

[0033] Figure 4 This is a comparison chart of the mass activity and area activity of the PtCo / C electrocatalysts prepared in Example 1 and Comparative Example 1 of this invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in more detail below with reference to the accompanying drawings and specific embodiments. However, the scope of protection of this invention is not limited to these embodiments. The same reference numerals throughout the text always represent the same elements, and similar reference numerals represent similar elements.

[0035] A method for preparing a carbon support for synthesizing catalysts with small and ordered particles specifically includes the following steps:

[0036] A method for preparing a carbon support for a catalyst with small and ordered particles, specifically including the following steps:

[0037] (1) Disperse the carbon support in the nitric acid solution and stir until homogeneous;

[0038] (2) The carbon support nitric acid solution obtained in step (1) is subjected to vacuum filtration and drying.

[0039] (3) Grind the carbon support obtained in step (2), then add a certain amount of sodium mercaptoacetate and water (the amount added should just cover the catalyst) to impregnate it, and then disperse it by ultrasonication and stir it evenly.

[0040] (4) The solution obtained in step (3) is dried, ground and then annealed in an inert atmosphere to obtain a carbon support for preparing the catalyst.

[0041] The stirring time in step (1) is 3-7 hours and the stirring speed is 300-500 r / min.

[0042] In step (1), the carbon carrier is carbon black.

[0043] The carbon support is either Vulcan XC-72 or Ketjen carbon black. Vulcan XC-72 is a conductive carbon black produced by Cabot Corporation of the United States, and Ketjen is a conductive carbon black produced by Lion Corporation of Japan.

[0044] The concentration of the nitric acid solution in step (1) is 0.8-1.2M, and the ratio of carbon support to nitric acid solution is 1g:200ml. The drying method in step (2) is rotary evaporation drying.

[0045] The mass ratio of carbon support to sodium mercaptoacetate in step (3) is (2-3):1.

[0046] The grinding time in step (3) is 10-30 minutes.

[0047] In step (3), the ultrasonic dispersion time is 30-60 min, the stirring time is 2-4 h, and the rotation speed is 50-70 r / min.

[0048] The inert atmosphere in step (4) is argon or nitrogen.

[0049] The annealing in step (4) is carried out in stages: first, the temperature is raised from room temperature to 650-750℃ at a rate of 5-20℃ / min, and the holding time is 2-3h, and then the temperature is automatically reduced.

[0050] A method for preparing a carbon support for synthesizing catalysts with small and ordered particles.

[0051] The above-mentioned carbon support is used in the synthesis of catalysts with small and ordered particles.

[0052] The carbon support is used for impregnation and reduction to prepare PtCo / C intermetallic compound catalysts with high metal content.

[0053] The method for preparing high-metal-content PtCo / C intermetallic compound catalysts by impregnation reduction is the same as the method for preparing carbon supports, except that the commercial carbon support impregnated with sodium mercaptoacetate is replaced with the carbon support prepared in this invention impregnated with an auxiliary precursor and a platinum salt precursor.

[0054] The molar ratio of the auxiliary precursor to the platinum salt precursor is 1-2:1, and the mass ratio of the carbon support, platinum salt precursor, and auxiliary precursor is 160-200:60-90:100-140.

[0055] The annealing process used in the impregnation reduction preparation of high metal content PtCo / C intermetallic compound catalyst is as follows: annealing temperature 700-800℃, holding time 1-3h, cooling to 550-650℃ and holding for another 1-3h.

[0056] The commercial carbon carrier used in the following examples is conductive carbon black manufactured by Lion Corporation of Japan, model Ketjen600.

[0057] Example 1

[0058] A carbon support for synthesizing catalysts with small and ordered particles is prepared by the following method:

[0059] (1) Disperse 1g of commercial carbon carrier Kotjen 600 into 200ml of 1M nitric acid solution and stir for 5h at a speed of 400r / min;

[0060] (2) The solution processed in step (1) is filtered and then dried by rotary evaporation. During the filtration process, 10L of ultrapure water is needed to rinse the surface nitric acid.

[0061] (3) Grind the carbon support after filtration and drying for half an hour, take 500 mg of the treated carbon support, add 188 mg of sodium mercaptoacetate and water to soak, ultrasonically disperse for 45 min, stir for 3 h, and rotate at 60 r / min.

[0062] (4) After drying and grinding the solution obtained in (3), it is placed in a tube furnace for annealing. In a nitrogen atmosphere, the temperature is raised from room temperature to 700°C and held for 2 hours before automatically cooling down. The heating rate is 10°C / min, and a carbon support for preparing the catalyst is obtained.

[0063] Example 2

[0064] A catalyst with small and ordered particles is prepared by the following method:

[0065] (1) Take 177 mg of the carbon support prepared in Example 1, add 200 mg of chloroplatinic acid, then add 95 mg of cobalt chloride hexahydrate, add water to soak, stir for 5 h, and rotate at 400 r / min.

[0066] (2) After drying and grinding the above solution for half an hour, the resulting solid powder is placed in a tube furnace for annealing. In a 5% hydrogen-argon mixed atmosphere, the temperature is raised from room temperature to 750°C and held for 2 hours at a rate of 10°C / min. Then, the temperature is lowered to 600°C and held for 2 hours at the same rate to obtain the PtCo / C catalyst.

[0067] Example 3

[0068] A catalyst with small and ordered particles is prepared by the following method:

[0069] (1) Take 177 mg of the carbon support prepared in Example 1, add 200 mg of chloroplatinic acid, then add 95 mg of cobalt chloride hexahydrate, add water to soak, and stir for 5 hours;

[0070] (2) After drying and grinding the above solution for half an hour, the resulting solid powder is placed in a tube furnace for annealing. In a 5% hydrogen-argon mixed atmosphere, the temperature is raised from room temperature to 850°C and held for 2 hours at a rate of 10°C / min. Then, the temperature is lowered to 600°C and held for 2 hours at the same rate to obtain the PtCo / C catalyst.

[0071] Comparative Example 1

[0072] Ketjen conductive carbon black manufactured by Lion Corporation of Japan was used as a comparative example.

[0073] Take 177 mg of the untreated conductive carbon black, add 200 mg of chloroplatinic acid, then add 95 mg of cobalt chloride hexahydrate, soak in water, stir overnight, dry the resulting solution, grind for half an hour, and then anneal the solid powder in a tube furnace. In a hydrogen-argon atmosphere, heat from room temperature to 750 °C and 850 °C and hold for 2 hours at a heating rate of 10 °C / min, and then cool down to 600 °C and hold for 2 hours at the same cooling rate to obtain the PtCo / C catalyst.

[0074] To compare the practicality of the prepared carbon support, the prepared catalyst was treated with sulfur, which made the catalyst particles smaller and increased the ordered phase. The particles of the sample without sulfur addition were larger than those of the sample without sulfur addition, mainly due to the interaction between sulfur and the support.

[0075] XRD tests were performed on the PtCo / C electrocatalysts prepared in Examples 2 and 3, both with and without sulfur treatment. The scanning range was 20-55°, and the scanning rate was 10° / min. The results are as follows: Figure 1 As shown. From Figure 1 It can be seen that the catalysts synthesized in Examples 2 and 3 have small particle sizes and obvious ordered phases; the half-peak width of the sulfur-doped sample is significantly narrower than that of the sulfur-doped sample, so the particles are larger.

[0076] The particle size of the PtCo / C electrocatalysts prepared in Examples 2 and 3 was tested, and the results are as follows: Figure 2 As shown, from Figure 2 It can be seen that the catalyst synthesized using this support still has a particle size of no more than 6 nm even at a temperature of 850 °C.

[0077] The prepared PtCo / C catalyst was dispersed in a mixed solution of isopropanol and water, and sonicated for 1 hour to ensure uniform dispersion. It was then dropped onto a glassy carbon electrode. After solvent evaporation in an isopropanol atmosphere, a half-cell test was performed on an electrochemical workstation. The test environment was a 0.1M HClO4 solution. Activation was first performed in an argon-saturated HClO4 solution, scanning back and forth within a voltage range of 0.05V to 1.1V. Then, its oxygen reduction activity was tested in an oxygen-saturated HClO4 solution, and the half-wave potential at 1600 rpm was measured with a scan rate of 10 mV / s. The polarization curve was obtained, as shown below. Figure 3 As shown, the catalyst synthesized using the carbon support prepared in Example 1 has significantly better performance than the commercial Pt / C catalyst.

[0078] XRD tests were performed on the PtCo / C electrocatalyst samples prepared from the untreated commercial carbon support of Comparative Example 1, both with and without sulfur treatment. The scanning range was 20-55°, and the scanning rate was 10° / min. The results are as follows: Figure 1 As shown. From Figure 1 It can be seen that the ordered phase of the catalyst obtained from carbon without sulfur treatment is relatively weak. The particle size of the prepared PtCo / C electrocatalyst was tested, and the results are as follows... Figure 2 As shown, from Figure 2 It can be seen that the catalyst prepared from commercial carbon supports without sulfur treatment has a larger particle size.

[0079] The PtCo / C catalyst prepared from the untreated commercial carbon support in Comparative Example 1 was dispersed in a mixed solution of isopropanol and water, sonicated for 1 hour, and then dropped onto a glassy carbon electrode. After the solvent evaporated in an isopropanol atmosphere, a half-cell test was performed on an electrochemical workstation. The test environment was a 0.1M HClO4 solution. Activation was first performed in an argon-saturated HClO4 solution, scanning back and forth within a voltage range of 0.05V to 1.1V. Then, its oxygen reduction activity was tested in an oxygen-saturated HClO4 solution, and the half-wave potential at 1600 rpm was measured with a scan rate of 10 mV / s. The polarization curve was obtained, as shown below. Figure 3 As shown.

[0080] The polarization curves of the PtCo / C catalyst prepared in Example 3 and the PtCo / C catalyst prepared with a commercial carbon support in Comparative Example 1 were compared in 0.1 M oxygen-saturated HClO4 solution. The comparison results are as follows: Figure 4 As shown, from Figure 4It can be seen that the mass activity of the PtCo / C catalyst prepared in Example 1 is almost twice that of the PtCo / C catalyst prepared with the commercial carbon support in Comparative Example 1, and the areal activity of the PtCo / C catalyst prepared in Example 1 is almost three times that of the PtCo / C catalyst prepared with the commercial carbon support in Comparative Example 1. At the same time, it is obvious that sulfur doping improves the electrochemical performance.

[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a carbon support for synthesizing a catalyst having small and ordered particles, characterized by, It comprises the following steps: (1) Disperse carbon carrier into nitric acid solution and stir evenly; the carbon carrier is one of Vulcan XC-72 or Ketjen carbon black; the stirring time is 3-7h, and the rotating speed is 300-500r / min; (2) Perform suction filtration and drying treatment on the carbon carrier nitric acid solution obtained in step (1); wash with ultrapure water after suction filtration; (3) Grind the carbon carrier obtained in step (2), then add sodium mercaptoacetate and immerse in water, and after ultrasonic dispersion, stir evenly; the mass ratio of carbon carrier to sodium mercaptoacetate is (2-3):1; the ultrasonic dispersion time is 30-60min, the stirring time is 2-4h, and the rotating speed is 50-70r / min; (4) The solution obtained in step (3) is dried and ground, and then annealed in an inert atmosphere to obtain a carbon carrier for preparing a catalyst; the annealing is performed in stages, and the annealing is first performed by increasing the temperature from room temperature to 650-750 o C at a rate of 5-20 ℃ / min, and the temperature is maintained for 2-3 h, and then the temperature is automatically decreased.

2. The carbon support production method according to claim 1, wherein The concentration of the nitric acid solution in step (1) is 0.8-1.2M, and the addition amount of the carbon carrier in the nitric acid solution is 0.03-0.07g / ml.

3. The carbon support production method according to claim 1, wherein The drying method in step (2) is rotary evaporation drying.

4. The carbon support production method according to claim 1, wherein The grinding time in step (3) is 10-30min.

5. The carbon support production method according to claim 1, wherein The inert atmosphere in step (4) is argon or nitrogen.

6. A carbon carrier prepared by the method of any one of claims 1-5.

7. Use of the carbon carrier of claim 6 in synthesizing a catalyst with small and ordered particles.

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