Carbon-supported platinum-cobalt intermetallic compound catalyst and preparation method thereof

Abstract

The invention belongs to the technical field of fuel cells, and provides a carbon-supported platinum-cobalt intermetallic compound catalyst and a preparation method thereof. The sulfur-containing carbon layer with the thickness of 0.5-1.5 nm is constructed on the surface of the platinum-cobalt intermetallic compound nano-particles, so that the dispersity of the platinum-cobalt intermetallic compound nano-particles in the catalyst is improved, and the catalytic performance and the stability of the catalyst are improved.

Description

Technical Field

[0001] The present invention relates to the field of fuel cell catalysts, and particularly to a carbon-supported platinum-cobalt intermetallic compound catalyst and a preparation method thereof. Background Art

[0002] As a light, efficient, and clean energy source, hydrogen can play an important role in addressing the challenges of global climate change. As a technology for efficiently utilizing renewable resources, fuel cells avoid heat energy loss compared to traditional internal combustion engines and have advantages such as high energy conversion efficiency, low pollution, and fast startup. Currently, commercially used catalysts still face problems such as high cost, insufficient stability, and easy poisoning and deactivation. One effective way to solve the above problems is to prepare platinum-cobalt intermetallic compounds. Compared with disordered alloys, ordered intermetallic compounds inhibit the excessive compression of the d-band center, making it closer to the theoretical optimal activity value. At the same time, the ordered intermetallic compounds have definite atomic positions and stoichiometry, with stronger interactions and better stability. Therefore, platinum-cobalt intermetallic compound catalysts have high catalytic activity and good durability.

[0003] In the synthesis process of intermetallic compounds, the phase transformation process from disordered alloys to ordered intermetallic compounds is a key step. During the phase transformation process, high temperatures above 600 °C and long times are often required to overcome the energy barrier of mutual diffusion. Inevitably, the high-temperature process will cause sintering of the catalyst, resulting in uneven distribution of nanoparticles in the catalyst, reducing the active sites of the catalyst, and seriously affecting the activity of the catalyst.

[0004] To improve the uniformity of the distribution of platinum-cobalt intermetallic compound nanoparticles in the catalyst, platinum intermetallic compounds with an average particle size of less than 5 nm were prepared on a porous sulfur-doped carbon support. The platinum precursor was impregnated on the sulfur-containing support, and the strong interaction between platinum and sulfur was used to anchor platinum on the surface of the support, thereby inhibiting metal sintering at up to 1000 °C during annealing. Unfortunately, the intermetallic compounds synthesized by this method have low order and complex processes, making it difficult to achieve mass production.

[0005] Therefore, developing a platinum-cobalt intermetallic compound catalyst with high catalytic activity, good durability, and easy mass production has extremely high application significance and challenges. Summary of the Invention

[0006] In order to improve the uniformity of the distribution of platinum-cobalt intermetallic compound nanoparticles in the catalyst, the present invention provides a carbon-supported platinum-cobalt intermetallic compound catalyst and a preparation method thereof.

[0007] A carbon layer containing sulfur elements with a thickness of 0.5 - 1.5 nm is constructed on the surface of the platinum-cobalt intermetallic compound nanoparticles in the present invention. Through the interaction between the sulfur element in the carbon layer and platinum, the problem that the platinum-cobalt intermetallic compound nanoparticles are prone to agglomeration and growth at high temperatures during phase transformation is effectively inhibited; by controlling the thickness of the carbon layer, the stability of the catalyst in the electrochemical environment is improved and the durability problem caused by the easy oxidation of cobalt during the use of the catalyst is effectively solved.

[0008] In the first aspect of the present invention, a carbon-supported platinum-cobalt intermetallic compound catalyst is provided, wherein there is a carbon layer containing sulfur elements with a thickness of 0.5 - 1.5 nm on the surface of the platinum-cobalt intermetallic compound nanoparticles supported on the carbon carrier, and the platinum-cobalt intermetallic compound particles are evenly dispersed on the carrier.

[0009] In some specific embodiments, the atomic ratio of platinum to cobalt in the platinum-cobalt intermetallic compound nanoparticles is 1:0.3 - 1.5; preferably, the atomic ratio of platinum to cobalt is 1:0.33 - 1.

[0010] In some specific embodiments, the source of the sulfur element is a small molecule compound containing a mercapto group. The molar ratio of the platinum precursor to the small molecule compound containing a mercapto group is (1:0.5) - (1:6).

[0011] In some specific embodiments, the small molecule compound containing a mercapto group is one or more of mercaptoacetic acid, ethanethiol, 1-propanethiol, 3-mercaptopropionic acid, 1,3-propanedithiol, glutathione, ammonium mercaptoacetate, cysteine, cysteine hydrochloride, 2-mercaptobenzimidazole, dimercaptosuccinic acid, and lipoic acid.

[0012] In some specific embodiments, the average particle size of the platinum-cobalt intermetallic compound nanoparticles is 2 - 4 nm.

[0013] In some specific embodiments, the platinum-cobalt intermetallic compound nanoparticles account for 20 - 50% of the total mass of the catalyst.

[0014] In the second aspect of the present invention, a preparation method of a carbon-supported platinum-cobalt intermetallic compound catalyst is provided, including the following steps:

[0015] S1: A small molecule compound containing a mercapto group and a metal precursor are placed in an acid solution and mixed evenly to obtain system A;

[0016] S2: A carbon carrier and system A are mixed evenly to obtain a dispersion of a mercapto small molecule coordinated carbon-supported platinum-cobalt precursor. After solid-liquid separation, a mercapto small molecule coordinated carbon-supported platinum-cobalt precursor B is obtained;

[0017] S3: Place the precursor B in a porcelain boat, perform high-temperature treatment under a reducing atmosphere, after cooling to room temperature, perform pickling and drying to obtain a carbon-supported platinum-cobalt intermetallic compound catalyst.

[0018] In some specific embodiments, the metal precursor in step S1 is one or more of chloroplatinic acid hexahydrate, platinum acetylacetonate, potassium chloroplatinate, cobalt acetylacetonate, cobalt nitrate hexahydrate, cobalt chloride hexahydrate, cobalt formate, and cobalt acetate tetrahydrate.

[0019] In some specific embodiments, the molar ratio of the platinum precursor to the thiol-containing small molecule compound in step S1 is 1:0.5 - 1:6; preferably, the molar ratio of the platinum precursor to the cobalt precursor is 1:0.5 - 1:2.5.

[0020] In some specific embodiments, the acid solution in step S1 includes one or more of hydrochloric acid, sulfuric acid, and perchloric acid.

[0021] In some specific embodiments, the concentration of the acid solution in step S1 is 0.01 - 0.5 mol / L.

[0022] In some specific embodiments, the carbon support in step S2 includes at least one of carbon powder, carbon black, and carbon nanotubes.

[0023] In some specific embodiments, the specific surface area of the carbon support in step S2 is 200 - 2000 m2 / g, and in some preferred specific embodiments, the specific surface area of the carbon support is 600 - 1500 m2 / g.

[0024] In some specific embodiments, the pore size distribution range of the carbon support in step S2 mainly concentrates between 1 - 7 nm, and in some preferred specific embodiments, the pore size of the carbon support concentrates between 2 - 4 nm.

[0025] In some specific embodiments, the reducing atmosphere in step S3 is selected from one or more of argon-hydrogen mixture, nitrogen-hydrogen mixture, and hydrogen.

[0026] In some specific embodiments, the volume ratio of the inert gas to hydrogen in the reducing atmosphere in step S3 is 9:1 - 19:1.

[0027] In some specific embodiments, the high-temperature treatment in step S3 includes a high-temperature section and an isothermal section.

[0028] In some specific embodiments, the treatment temperature of the high-temperature section in step S3 is 800°C - 1000°C.

[0029] In some specific embodiments, the treatment duration of the high-temperature section in step S3 is 1 - 10 h.

[0030] In some specific embodiments, the treatment temperature in the constant temperature section in step S3 is 500°C - 700°C.

[0031] In some specific embodiments, the treatment temperature in the constant temperature section in step S3 is 600°C.

[0032] In some specific embodiments, the treatment duration in the constant temperature section in step S3 is 1 - 10 h.

[0033] In some specific embodiments, the washing temperature in step S3 is 40°C - 80°C;

[0034] In some specific embodiments, the drying temperature in step S3 is 40°C - 80°C;

[0035] The third aspect of the present invention lies in providing the application of the carbon-supported platinum-cobalt intermetallic compound catalyst in the catalyst of a proton exchange membrane fuel cell.

[0036] The present invention has the following advantages and beneficial effects:

[0037] In the present invention, a small molecule compound containing a mercapto group with strong complexing action is complexed with a platinum salt and a cobalt salt in a specific acidic environment to ensure uniform distribution of the metal precursor on the surface of the carrier. Subsequently, reduction is carried out through a specific formulation process, such that a part of the small molecule compound containing a mercapto group has its sulfur-containing group migrate to the surface of the carbon carrier during the high-temperature treatment process, and another part of the small molecule migrates to the surface of the catalyst to form a carbon-coated layer, thereby constructing a sulfur-containing carbon layer with a thickness of 0.5 - 1.5 nm on the surface of the reduced platinum-cobalt intermetallic compound nanoparticles, improving the dispersibility of the platinum-cobalt intermetallic compound nanoparticles in the catalyst, and enhancing the catalytic performance and stability of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The following further illustrates the present invention in conjunction with the drawings and embodiments.

[0039] Figure 1 It is the XRD pattern of the catalyst prepared in Example 1.

[0040] Figure 2 It is the TEM pattern of the catalyst prepared in Example 1.

[0041] Figure 3 It is the XRD pattern of the catalysts prepared in Example 6 and Comparative Example 4.

[0042] Figure 4 It is the comparison chart of the LSV curves of the catalyst prepared in Example 1 and Comparative Example 1.

[0043] Figure 5 It is the TEM pattern of the catalyst prepared in Example 1.

[0044] Figure 6 TEM image of the catalyst prepared in Comparative Example 2.

[0045] Figure 7 TEM image of the catalyst prepared in Comparative Example 3.

[0046] Figure 8 LSV curve of the catalyst prepared in Example 6.

[0047] Figure 9 XPS image of the catalyst prepared in Example 1. Detailed implementation manners

[0048] In order to further explain the technical solution of the present invention, the present invention will be elaborated in detail through specific examples below.

[0049] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the specific implementation manners of the present invention will be described in detail below in conjunction with the embodiments of the specification.

[0050] Many specific details are set forth in the following description in order to provide a thorough understanding of the present invention. However, the present invention may be practiced in other ways than those specifically described herein. Those skilled in the art can make similar extensions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0051] Secondly, the so-called "one embodiment" or "embodiment" herein refers to a specific feature, structure or characteristic that may be included in at least one implementation manner of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that excludes other embodiments.

[0052] Example 1:

[0053] (1) Measure 200 mL of 0.1 mol / L hydrochloric acid solution into a 500 mL round-bottom flask, and then add 672.88 mg of chloroplatinic acid hexahydrate, 143.43 mg of cysteine hydrochloride, and 463.74 mg of cobalt chloride hexahydrate. After the reactants are fully coordinated, system A is obtained.

[0054] (2) Weigh 670 mg of carbon black (specific surface area is 750 m2 / g, pore size distribution is 2 - 4 nm) and place it in reaction system A. After sufficient dispersion, place the reaction system on a rotary evaporator. After solid-liquid separation, reaction system B is obtained.

[0055] (3) Place the powder in the reaction system B in a porcelain boat, and in a tubular furnace with an argon-hydrogen mixed gas atmosphere containing 5 Vol% H2, heat it to 900 °C at a rate of 10 °C / min, perform high-temperature treatment at 900 °C for 2 h, then cool it to 600 °C at a rate of 1 °C / min, keep it at a constant temperature of 600 °C for 6 h, and naturally cool it to room temperature. After pickling in a 0.01 mol / L hydrochloric acid solution at 40 °C, then wash it 3 times in an aqueous solution, and dry it at 60 °C to obtain a carbon-supported platinum-cobalt intermetallic compound catalyst with a metal loading of 33%, a sulfur-containing carbon layer with a thickness of 1 nm on the surface, a platinum-cobalt atomic ratio of 1:1, and an average particle size of 3 nm.

[0056] Example 2:

[0057] (1) Measure 200 mL of 0.01 mol / L perchloric acid solution into a 500 mL round-bottom flask, and then add 464.52 mg of chloroplatinic acid hexahydrate, 82.61 mg of thioglycolic acid, and 652.68 mg of cobalt nitrate hexahydrate. After the reactants are fully coordinated, system A is obtained.

[0058] (2) Weigh 700 mg of carbon black (specific surface area is 1250 m 2 / g, pore size distribution is 2 - 4 nm) carbon powder and place it in reaction system A. After full dispersion, place the reaction system on a rotary evaporator, and after solid-liquid separation, reaction system B is obtained.

[0059] (3) Place the powder in the reaction system B in a porcelain boat, and in a tubular furnace with an argon-hydrogen mixed gas atmosphere containing 5 Vol% H2, heat it to 1000 °C at a rate of 10 °C / min, perform high-temperature treatment at 1000 °C for 2 h, then slowly cool it to 600 °C at a rate of 2 °C / min, keep it at a constant temperature of 600 °C for 1 h, and naturally cool it to room temperature. After pickling in a 0.5 mol / L perchloric acid solution at 80 °C, then wash it 6 times in an aqueous solution, and dry it at 80 °C to obtain a carbon-supported platinum-cobalt intermetallic compound catalyst with a metal loading of 30%, a sulfur-containing carbon layer with a thickness of 1.5 nm on the surface, a platinum-cobalt atomic ratio of 1:1.5, and an average particle size of 4 nm.

[0060] Example 3:

[0061] (1) Measure 200 mL of 0.5 mol / L sulfuric acid solution into a 500 mL round-bottom flask, and then add 765.35 mg of potassium chloroplatinate, 97.83 mg of ethanethiol, and 561.04 mg of cobalt acetylacetonate. After the reactants are fully coordinated, system A is obtained.

[0062] (2) Weigh 400 mg of carbon black (specific surface area is 250 m2 / g, pore size distribution is 2 - 4 nm) carbon powder and place it in reaction system A. After full dispersion, place the reaction system on a rotary evaporator, and after solid-liquid separation, reaction system B is obtained.

[0063] (3) Place the powder in the reaction system B in a porcelain boat. In a tubular furnace with an argon-hydrogen mixed gas atmosphere containing 10 Vol% H2, heat it to 900 °C at a rate of 10 °C / min for high-temperature treatment for 2 h, then slowly cool it to 600 °C at a rate of 5 °C / min, keep it at a constant temperature of 600 °C for 6 h, and naturally cool it to room temperature. After pickling in a 0.5 mol / L hydrochloric acid solution at 40 °C, then wash it 6 times in an aqueous solution, and dry it at 40 °C to obtain a carbon-supported platinum-cobalt intermetallic compound catalyst with a metal loading of 50%, a 1-nm sulfur-containing carbon layer on the surface, a platinum-cobalt atomic ratio of 1:0.7, and an average particle size of 4 nm.

[0064] Example 4:

[0065] (1) Measure 200 mL of 0.2 mol / L perchloric acid solution into a 500-mL round-bottom flask, and then add 611.81 mg of chloroplatinic acid hexahydrate, 87.75 mg of mercaptopropionic acid, and 562.21 mg of cobalt chloride hexahydrate. After the reactants are fully coordinated, system A is obtained.

[0066] (2) Weigh 700 mg of carbon nanotubes (specific surface area: 280 m2 / g) and place them in reaction system A. After full dispersion, place the reaction system on a rotary evaporator, and after solid-liquid separation, reaction system B is obtained.

[0067] (3) Place the powder in the reaction system B in a porcelain boat. In a tubular furnace with an argon-hydrogen mixed gas atmosphere containing 5 Vol% H2, heat it to 950 °C at a rate of 10 °C / min for high-temperature treatment for 2 h, then slowly cool it to 600 °C at a rate of 5 °C / min, keep it at a constant temperature of 600 °C for 5 h, and naturally cool it to room temperature. After pickling in a 0.25 mol / L sulfuric acid solution at 60 °C, then wash it 6 times in an aqueous solution, and dry it at 60 °C to obtain a carbon-supported platinum-cobalt intermetallic compound catalyst with a metal loading of 30%, a 1-nm sulfur-containing carbon layer on the surface, a platinum-cobalt atomic ratio of 1:1.5, and an average particle size of 4 nm.

[0068] Example 5:

[0069] (1) Measure 240 mL of 0.2 mol / L perchloric acid solution into a 500-mL round-bottom flask, and then add 407.87 mg of chloroplatinic acid hexahydrate, 241.98 mg of glutathione, and 392.25 mg of cobalt acetate tetrahydrate. After the reactants are fully coordinated, system A is obtained.

[0070] (2) Weigh 800 mg of carbon nanotubes (specific surface area: 200 m2 / g) and place them in reaction system A. After full dispersion, place the reaction system on a rotary evaporator, and after solid-liquid separation, reaction system B is obtained.

[0071] (3) Place the powder in the reaction system B in a porcelain boat, and in a tubular furnace with an argon-hydrogen mixed gas atmosphere containing 5 Vol% H2, heat it from room temperature to 950 °C at a rate of 10 °C / min for 2 h of high-temperature treatment, then slowly cool it to 600 °C at a rate of 4 °C / min, keep it at a constant temperature of 600 °C for 5 h, and then naturally cool it to room temperature. After pickling in a 0.1 mol / L perchloric acid solution at 60 °C, wash it 6 times in an aqueous solution, and dry it at 60 °C to obtain a carbon-supported platinum-cobalt intermetallic compound catalyst with a metal loading of 20%, a 1-nm sulfur-containing carbon layer on the surface, a platinum-cobalt atomic ratio of 1:1.5, and an average particle size of 3 nm.

[0072] Example 6:

[0073] (1) Measure 240 mL of 0.1 mol / L hydrochloric acid solution into a 500-mL round-bottom flask, and then add 672.88 mg of chloroplatinic acid hexahydrate, 143.43 mg of cysteine hydrochloride, and 154.58 mg of cobalt chloride hexahydrate to make the reactants fully coordinate to obtain system A.

[0074] (2) Weigh 670 mg of carbon black (specific surface area is 750 m2 / g, pore size distribution is 2 - 4 nm) and place it in reaction system A. After full dispersion, place the reaction system on a rotary evaporator, and after solid-liquid separation, obtain reaction system B.

[0075] (3) Place the powder in the reaction system B in a porcelain boat, and in a tubular furnace with an argon-hydrogen mixed gas atmosphere containing 5 Vol% H2, heat it from room temperature to 900 °C at a rate of 10 °C / min for 2 h of high-temperature treatment, then slowly cool it to 600 °C at a rate of 1 °C / min, keep it at a constant temperature of 600 °C for 6 h, and then naturally cool it to room temperature. After pickling in a 0.01 mol / L sulfuric acid solution at 80 °C, wash it 6 times in an aqueous solution, and dry it at 60 °C to obtain a carbon-supported platinum-cobalt intermetallic compound catalyst with a metal loading of 30%, a 1-nm sulfur-containing carbon layer on the surface, a platinum-cobalt atomic ratio of 1:0.5, and an average particle size of 3 nm.

[0076] Example 7:

[0077] (1) Measure 240 mL of 0.1 mol / L perchloric acid solution into a 500-mL round-bottom flask, and then add 672.88 mg of chloroplatinic acid hexahydrate, 70.89 mg of ammonium thioglycolate, and 154.58 mg of cobalt chloride hexahydrate to make the reactants fully coordinate to obtain system A.

[0078] (2) Weigh 670 mg of carbon black (specific surface area is 1250 m2 / g, pore size distribution is 2 - 4 nm) and place it in reaction system A. After full dispersion, place the reaction system on a rotary evaporator, and after solid-liquid separation, obtain reaction system B.

[0079] (3) Place the powder in the reaction system B in a porcelain boat. In a tubular furnace with an argon-hydrogen mixed gas atmosphere containing 5 Vol% H2, heat it to 900 °C at a rate of 10 °C / min for high-temperature treatment for 2 h, then slowly cool it to 600 °C at a rate of 1 °C / min, keep it at a constant temperature of 600 °C for 6 h, and naturally cool it to room temperature. After pickling in an 80 °C 0.01 mol / L sulfuric acid solution, then wash it 6 times in an aqueous solution, and dry it at 60 °C to obtain a carbon-supported platinum-cobalt intermetallic compound catalyst with a metal loading of 30%, a sulfur-containing carbon layer with a thickness of 0.5 nm on the surface, a platinum-cobalt atomic ratio of 1:0.5, and an average particle size of 4 nm.

[0080] Example 8:

[0081] (1) Measure 240 mL of 0.5 mol / L hydrochloric acid solution into a 500 mL round-bottom flask, and then add 672.88 mg of chloroplatinic acid hexahydrate, 1.17 g of 2-mercaptobenzimidazole, and 154.58 mg of cobalt chloride hexahydrate. The reactants are fully coordinated to obtain system A.

[0082] (2) Weigh 670 mg of carbon black (specific surface area is 750 m2 / g, pore size distribution is 2 - 4 nm) and place it in reaction system A. After full dispersion, place the reaction system on a rotary evaporator, and after solid-liquid separation, obtain reaction system B.

[0083] (3) Place the powder in the reaction system B in a porcelain boat. In a tubular furnace with an argon-hydrogen mixed gas atmosphere containing 10 Vol% H2, heat it to 950 °C at a rate of 10 °C / min for high-temperature treatment for 1 h, then slowly cool it to 600 °C at a rate of 5 °C / min, keep it at a constant temperature of 600 °C for 8 h, and naturally cool it to room temperature. After pickling in an 80 °C 0.5 mol / L sulfuric acid solution, then wash it 6 times in an aqueous solution, and dry it at 60 °C to obtain a carbon-supported platinum-cobalt intermetallic compound catalyst with a metal loading of 30%, a sulfur-containing carbon layer with a thickness of 1.5 nm on the surface, a platinum-cobalt atomic ratio of 1:0.5, and an average particle size of 2 nm.

[0084] Example 9:

[0085] (1) Measure 240 mL of 0.5 mol / L hydrochloric acid solution into a 500 mL round-bottom flask, and then add 510.89 mg of platinum acetylacetonate, 165.82 mg of 2,3-dimercaptosuccinic acid, and 154.58 mg of cobalt chloride hexahydrate. The reactants are fully coordinated to obtain system A.

[0086] (2) Weigh 670 mg of carbon black (specific surface area is 750 m2 / g, pore size distribution is 2 - 4 nm) and place it in reaction system A. After full dispersion, place the reaction system on a rotary evaporator, and after solid-liquid separation, obtain reaction system B.

[0087] (3) Place the powder in the reaction system B in a porcelain boat. In a tubular furnace with an argon-hydrogen mixed gas atmosphere containing 10 Vol% H2, heat it from room temperature to 950 °C at a rate of 10 °C / min for high-temperature treatment for 1 h, then slowly cool it to 600 °C at a rate of 5 °C / min, keep it at a constant temperature of 600 °C for 8 h, and then cool it naturally to room temperature. After pickling in an 80 °C 0.5 mol / L sulfuric acid solution, wash it 6 times in an aqueous solution, and dry it at 60 °C to obtain a carbon-supported platinum-cobalt intermetallic compound catalyst with a metal loading of 30%, a 1-nm sulfur-containing carbon layer on the surface, a platinum-cobalt atomic ratio of 1:0.8, and an average particle size of 3 nm.

[0088] Example 10:

[0089] (1) Measure 240 mL of 0.25 mol / L hydrochloric acid solution into a 500 mL round-bottom flask, and then add 672.88 mg of chloroplatinic acid hexahydrate, 187.76 mg of lipoic acid, and 154.58 mg of cobalt chloride hexahydrate, and stir for 10 min to make the reactants fully coordinate to obtain system A.

[0090] (2) Weigh 670 mg of carbon black (specific surface area of 1250 m2 / g, pore size distribution of 2 - 4 nm) and place it in reaction system A. After sufficient dispersion, place the reaction system on a rotary evaporator and perform solid-liquid separation to obtain reaction system B.

[0091] (3) Place the powder in the reaction system B in a porcelain boat. In a tubular furnace with an argon-hydrogen mixed gas atmosphere containing 5 Vol% H2, heat it from room temperature to 950 °C at a rate of 10 °C / min for high-temperature treatment for 1 h, then slowly cool it to 600 °C at a rate of 5 °C / min, keep it at a constant temperature of 600 °C for 8 h, and then cool it naturally to room temperature. After pickling in an 80 °C 0.5 mol / L sulfuric acid solution, wash it 6 times in an aqueous solution, and dry it at 60 °C to obtain a carbon-supported platinum-cobalt intermetallic compound catalyst with a metal loading of 30%, a 1-nm sulfur-containing carbon layer on the surface, a platinum-cobalt atomic ratio of 1:0.7, and an average particle size of 3 nm.

[0092] Example 11:

[0093] (1) Measure 240 mL of 0.25 mol / L hydrochloric acid solution into a 500 mL round-bottom flask, and then add 672.88 mg of chloroplatinic acid hexahydrate, 69.31 mg of 1-propanethiol, and 154.58 mg of cobalt chloride hexahydrate, and stir for 10 min to make the reactants fully coordinate to obtain system A.

[0094] (2) Weigh 670 mg of carbon black (specific surface area of 1250 m2 / g, pore size distribution of 2 - 4 nm) and place it in reaction system A. After sufficient dispersion, place the reaction system on a rotary evaporator and perform solid-liquid separation to obtain reaction system B.

[0095] (3) The powder in reaction system B is placed in a porcelain boat, and in a tubular furnace containing 5Vol% H2 in an argon-hydrogen mixed gas atmosphere, the temperature is raised to 950°C at a rate of 10°C / min for high temperature treatment for 1h, then slowly cooled to 600°C at a rate of 5°C / min, kept at 600°C for 8h, and naturally cooled to room temperature. After acid washing in 0.5mol / L hydrochloric acid solution at 80°C, it is then washed 6 times in an aqueous solution, and dried at 60°C to obtain a carbon-supported platinum-cobalt intermetallic compound catalyst with a metal loading of 30%, a 1nm sulfur-containing carbon layer on the surface, a platinum-cobalt atomic ratio of 1:0.5, and an average particle size of 3nm.

[0096] Embodiment 12:

[0097] (1) 240 mL of 0.25 mol / L hydrochloric acid solution was weighed and placed in a 500 mL round-bottom flask, and 672.88 mg of chloroplatinic acid hexahydrate, 98.51 mg of 1,3-propanedithiol and 96.76 mg of cobalt formate were added. The reactants were fully coordinated to obtain system A.

[0098] (2) Weigh 670 mg of carbon black (specific surface area of ​​1250 m2 / g, pore size distribution of 2-4 nm) and place it in reaction system A and fully disperse it. Place the reaction system on a rotary evaporator and obtain reaction system B after solid-liquid separation.

[0099] (3) The powder in reaction system B is placed in a porcelain boat, and in a tubular furnace containing 5Vol% H2 in an argon-hydrogen mixed gas atmosphere, the temperature is raised to 950°C at a rate of 10°C / min for high temperature treatment for 1h, then slowly cooled to 600°C at a rate of 5°C / min, kept at 600°C for 8h, and naturally cooled to room temperature. After acid washing in 80°C 0.5mol / L hydrochloric acid solution, it is then washed 6 times in an aqueous solution, and dried at 60°C to obtain a carbon-supported platinum-cobalt intermetallic compound catalyst with a metal loading of 30%, a 1.5nm sulfur-containing carbon layer on the surface, a platinum-cobalt atomic ratio of 1:0.7, and an average particle size of 4nm.

[0100] Comparative Example 1:

[0101] The catalyst is a 40% platinum-carbon catalyst produced by Johnson Matthey Company.

[0102] Comparative Example 2:

[0103] (1) 240 mL of the aqueous solution was weighed and placed in a 500 mL round-bottom flask, and 672.88 mg of chloroplatinic acid hexahydrate, 99.64 mg of ammonium thioglycolate and 463.74 mg of cobalt chloride hexahydrate were added. The reactants were fully coordinated to obtain system A.

[0104] (2) Weigh 670 mg of carbon black (specific surface area is 750 m2 / g, pore size distribution is 2 - 4 nm) and place it in reaction system A. After sufficient dispersion, place the reaction system on a rotary evaporator. After solid-liquid separation, reaction system B is obtained.

[0105] (3) Place the powder in reaction system B in a porcelain boat. In a tubular furnace with an argon-hydrogen mixed gas atmosphere containing 5 Vol% H2, heat it to 900 °C at a rate of 10 °C / min for high-temperature treatment for 2 h, then slowly cool it to 600 °C at a rate of 1 °C / min, keep it at a constant temperature of 600 °C for 6 h, and then naturally cool it to room temperature. After pickling in a 0.1 mol / L perchloric acid solution at 60 °C, wash it 6 times in an aqueous solution, and dry it at 60 °C to obtain a carbon-supported platinum-cobalt intermetallic compound catalyst with a metal loading of 33%, a sulfur-containing carbon layer with a thickness of 1.5 nm on the surface, a platinum-cobalt atomic ratio of 1:1, and an average particle size of 5 nm.

[0106] Comparative Example 3:

[0107] (1) Measure 240 mL of 0.2 mol / L perchloric acid solution into a 500 mL round-bottom flask, and then add 672.88 mg of chloroplatinic acid hexahydrate, 965.13 mg of mercaptopropionic acid, and 463.74 mg of cobalt chloride hexahydrate. The reactants are fully coordinated to obtain system A.

[0108] (2) Weigh 670 mg of carbon nanotubes (specific surface area is 280 m2 / g) and place it in reaction system A. After sufficient dispersion, place the reaction system on a rotary evaporator. After solid-liquid separation, reaction system B is obtained.

[0109] (3) Place the powder in reaction system B in a porcelain boat. In a tubular furnace with an argon-hydrogen mixed gas atmosphere containing 5 Vol% H2, heat it to 900 °C at a rate of 10 °C / min for high-temperature treatment for 2 h, then slowly cool it to 600 °C at a rate of 1 °C / min, keep it at a constant temperature of 600 °C for 6 h, and then naturally cool it to room temperature. After pickling in a 0.1 mol / L perchloric acid solution at 60 °C, wash it 6 times in an aqueous solution, and dry it at 60 °C to obtain a carbon-supported platinum-cobalt intermetallic compound catalyst with a metal loading of 33%, a sulfur-containing carbon layer with a thickness of 3 nm on the surface, a platinum-cobalt atomic ratio of 1:1, and an average particle size of 4 nm.

[0110] Comparative Example 4

[0111] (1) Measure 240 mL of aqueous solution into a 500 mL round-bottom flask, and then add 672.88 mg of chloroplatinic acid hexahydrate and 154.58 mg of cobalt chloride hexahydrate to dissolve them fully to obtain system A.

[0112] (2) Weigh 670 mg of carbon black (specific surface area is 750 m2 / g, pore size distribution is 2 - 4 nm) and place it in reaction system A. After sufficient dispersion, place the reaction system on a rotary evaporator. After solid-liquid separation, reaction system B is obtained.

[0113] (3) Place the powder in reaction system B in a porcelain boat. In a tubular furnace with an argon-hydrogen mixed gas atmosphere containing 5 Vol% H2, heat it at a rate of 10 °C / min to 900 °C for high-temperature treatment for 2 h, then slowly cool it to 600 °C at a rate of 1 °C / min, keep it at a constant temperature of 600 °C for 6 h, and naturally cool it to room temperature. After pickling in a 60 °C 0.1 mol / L perchloric acid solution, then wash it 6 times in an aqueous solution, and dry it at 60 °C to obtain a carbon-supported platinum-cobalt intermetallic compound catalyst with a metal loading of 30%, a platinum-cobalt atomic ratio of 1:0.5, and an average particle size of 8 nm.

[0114] Perform X-ray diffraction (XRD) tests, transmission electron microscopy (TEM) tests, and X-ray photoelectron spectroscopy (XPS) tests on the catalysts prepared in the examples and comparative examples. The test results are as follows:

[0115] Figure 1 This is the XRD pattern of the catalyst prepared in Example 1. It can be seen from the figure that the sample has the diffraction peaks characteristic of a face-centered tetragonal structure (fct), indicating that an intermetallic compound structure has been formed.

[0116] Figure 2 This is the TEM image of the catalyst prepared in Example 1. It can be seen from the figure that the surface of the sample has a sulfur-containing carbon layer of about 1 nm.

[0117] Figure 3 This is the XRD pattern of the catalysts prepared in Example 6 and Comparative Example 4. It can be seen that phase separation occurred in Comparative Example 4 where no small molecule compounds containing mercapto groups participated in the preparation.

[0118] Figure 5 This is the TEM image of the catalyst prepared in Example 1. It can be seen that the platinum-cobalt intermetallic compound particles are evenly dispersed on the carrier.

[0119] Figure 6 This is the TEM image of the catalyst prepared in Comparative Example 2. Since Comparative Example 2 was not prepared in an acid solution, partial agglomeration of the platinum-cobalt intermetallic compound nanoparticles occurred on the carbon carrier.

[0120] Figure 7 This is the TEM image of the catalyst prepared in Comparative Example 3. A higher small molecule ratio in the acidic coordination environment resulted in an overly thick carbon layer (greater than 2 nm) on the surface of the platinum-cobalt intermetallic particles.

[0121] Figure 9The XPS spectrum of the catalyst prepared in Example 1 proves the existence of sulfur element in the carbon layer on the catalyst surface, and the sulfur element still exists after the etching depth reaches 5 nm and 10 nm.

[0122] The oxygen reduction (ORR) catalytic activity of the catalysts in Example 1 and Comparative Example 1 was tested under a three-electrode test system. The specific test conditions are as follows:

[0123] 1. The working electrode is a glassy carbon electrode, the counter electrode is a graphite electrode, and the reference electrode is a saturated calomel electrode.

[0124] 2. The test environment is an O2-saturated 0.1 mol / L HClO4 solution. The scanning potential range is -0.27 to 0.8 V, the scanning rate is 10 mV / s, and the rotation speed of the working electrode is 1600 rpm.

[0125] 3. The catalyst slurry composition includes 1.5 mg of catalyst, 790 μL of isopropanol, 200 μL of ultrapure water, and 10 μL of Nafion solution. All the above components are placed in a 2 mL vial and sonicated in cold water for 30 min until the slurry is uniform.

[0126] 4. Take 10 μL of the catalyst slurry and drop it on the glassy carbon electrode in two portions. After drying under an infrared lamp, the ORR activity test is carried out. The accelerated durability test of the catalyst in Example 6 was carried out under a three-electrode test system. The specific test conditions are as follows:

[0127] 1. The working electrode is a glassy carbon electrode, the counter electrode is a graphite electrode, and the reference electrode is a saturated calomel electrode.

[0128] 2. The test environment is an O2-saturated 0.1 mol / L HClO4 solution. The scanning potential range is 0.6 to 1.1 V (vs. RHE), the scanning rate is 10 mV / s, and it is cycled 30,000 times.

[0129] 3. After the catalyst durability test, the ORR activity test is carried out again and compared with that before the durability test.

[0130] Through the comparison chart of the LSV curves of the catalyst prepared in Example 1 and Comparative Example 1 ( Figure 4 ), it can be seen that the half-wave potential of Example 1 is 0.934 V, which is better than 0.906 V of Comparative Example 1, indicating that the ORR catalytic activity of the catalyst in Example 1 is better than that of the commercial catalyst.

[0131] Through the LSV curve of Example 6 ( Figure 8 ), it can be seen that the performance of the catalyst does not show obvious decline after 30,000 cycles.

[0132] The above is only a preferred embodiment of the present invention, and thus the scope of implementation of the present invention cannot be limited thereby. That is, equivalent changes and modifications made according to the scope of the present invention patent and the content of the specification should still fall within the scope covered by the present invention.

Claims

1. A carbon-supported platinum-cobalt intermetallic compound catalyst, characterized in that, There is a carbon layer containing sulfur element with a thickness of 0.5 - 1.5 nm on the surface of platinum-cobalt intermetallic compound nanoparticles supported on a carbon carrier.

2. The carbon-supported platinum-cobalt intermetallic compound catalyst according to claim 1, wherein The source of the sulfur element is a small molecule compound containing a mercapto group; the small molecule compound containing a mercapto group is one or more of mercaptoacetic acid, ethanethiol, 1-propanethiol, mercaptopropionic acid, 1,3-propanedithiol, glutathione, ammonium mercaptoacetate, cysteine, cysteine hydrochloride, 2-mercaptobenzimidazole, dimercaptosuccinic acid, and lipoic acid.

3. The carbon-supported platinum-cobalt intermetallic compound catalyst according to claim 1, wherein The atomic ratio of platinum to cobalt in the platinum-cobalt intermetallic compound nanoparticles is 1:0.3 - 1.5; preferably, the atomic ratio of platinum to cobalt is 1:0.33 - 1.

4. The carbon-supported platinum-cobalt intermetallic compound catalyst according to claim 1, wherein The average particle size of the platinum-cobalt intermetallic compound nanoparticles is 2 - 4 nm.

5. The carbon-supported platinum-cobalt intermetallic compound catalyst according to claim 1, wherein The platinum-cobalt intermetallic compound nanoparticles account for 20 - 50% of the total mass of the catalyst.

6. Use of the carbon-supported platinum-cobalt intermetallic compound catalyst according to any one of claims 1 to 5 in a proton exchange membrane fuel cell catalyst.

7. A preparation method of the carbon-supported platinum-cobalt intermetallic compound catalyst according to any one of claims 1 to 5, characterized in that, Comprising the following steps: S1: A small molecule compound containing a mercapto group and a metal precursor are placed in an acid solution and mixed evenly to obtain system A; S2: The carbon carrier and system A are mixed evenly to obtain a mercapto small molecule coordinated carbon-supported platinum-cobalt precursor dispersion liquid. After solid-liquid separation, a mercapto small molecule coordinated carbon-supported platinum-cobalt precursor B is obtained; S3: The precursor B is placed in a porcelain boat and subjected to high-temperature treatment in a reducing atmosphere. After cooling to room temperature, pickling and drying are carried out to obtain a carbon-supported platinum-cobalt intermetallic compound catalyst.

8. The preparation method of the carbon-supported platinum-cobalt intermetallic compound catalyst according to claim 7, characterized in that, In step S1, the metal precursor is one or more of chloroplatinic acid hexahydrate, platinum acetylacetonate, potassium chloroplatinate, cobalt acetylacetonate, cobalt nitrate, cobalt chloride hexahydrate, cobalt formate, and cobalt acetate; the molar ratio of the metal precursor to the small molecule compound containing a mercapto group is 1:0.5 - 1:6; preferably, the molar ratio is 1:0.5 - 1:2.

5.

9. The preparation method of the carbon-supported platinum-cobalt intermetallic compound catalyst according to claim 7, characterized in that, In step S1 or S3, the concentration of the acid solution is 0.01 - 0.5 mol / L.

10. The preparation method of the carbon-supported platinum-cobalt intermetallic compound catalyst according to claim 7, wherein, The high-temperature treatment in step S3 includes a high-temperature section and an isothermal section. The temperature of the high-temperature section is 800°C - 1000°C, and the temperature of the isothermal section is 500°C - 700°C.

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