A method for synthesizing a transition metal phosphide Pt-based composite catalyst with adjustable morphology

Abstract

The present invention belongs to the field of electrocatalysis technology, and specifically relates to a method for synthesizing a transition metal phosphide Pt-based composite catalyst with adjustable morphology, including preparing a precursor Fe-DCD, preparing a Fe-Co-DCD precursor, preparing a composite support, and preparing a composite catalyst. Hydrangea-shaped, spherical, and lamellar Pt / Fe2P-CoP-NDC composite catalysts can be obtained by the method of the present invention. Compared with the existing granular form, the present invention increases the specific surface area and improves the pore structure, which can accelerate the reaction kinetics and reaction process of methanol oxidation. At the same time, by regulating the morphology, the interaction force between Pt NPs and the carrier material can be effectively enhanced, the catalytic stability of the Pt-based catalyst in the methanol oxidation reaction can be improved, and the optimization of the Pt particle size, dispersion, surface state, exposed crystal surface, number of active sites, and resistance to CO poisoning plays a key role, thereby improving the catalytic activity of the Pt-based catalyst.

Description

Technical Field

[0001] The invention belongs to the technical field of electrocatalysis, and in particular relates to a method for synthesizing a transition metal phosphide Pt-based composite catalyst with controllable morphology. Background Art

[0002] As an energy conversion device, direct methanol fuel cells (DMFCs) have attracted extensive research due to their high energy conversion efficiency, abundant fuel sources, easy storage, and low pollution emissions. Currently, the lack of efficient DMFC anode catalysts is one of the main limitations on their large-scale commercial application. Numerous studies have shown that the precious metal Pt remains the best choice for catalytic methanol oxidation. However, Pt is expensive and easily poisoned by the intermediate CO. Therefore, achieving small-sized dispersion of Pt nanoparticles and increasing the utilization of the precious metal Pt are of great significance for reducing costs and improving the methanol oxidation activity of Pt-based composite catalysts.

[0003] Transition metal phosphides have attracted extensive attention due to their excellent catalytic effect. In the process of methanol oxidation, the metal center M δ+ and P δ- Active sites can play a significant promoting role, activating water molecules at a lower potential, accelerating the decomposition of H2O, generating abundant hydroxyl groups to participate in the reaction, and removing CO-like intermediates chemically adsorbed on the active sites of Pt nanoparticles, thereby releasing more active sites to participate in the reaction and increasing the utilization rate of precious metals. At the same time, based on the bifunctional mechanism and electronic effect, the embedding of transition metal phosphides can significantly improve the methanol oxidation activity of the catalyst. However, transition metal phosphides have poor stability and mostly exist in the form of particles. During the electrocatalytic process, they inevitably agglomerate and dissolve, resulting in the burial of the catalyst active sites and reduced catalytic activity and stability. Therefore, precise control of their morphology and structure has a significant impact on optimizing the size, dispersion, and surface state of Pt nanoparticles.

[0004] To date, precise control of the morphology and structure of Pt-based catalysts based on transition metal phosphides has been rare. Therefore, the screening and construction of inexpensive, readily available, and high-performance electrocatalytic materials is crucial for promoting the large-scale commercialization of DMFCs. Generally, a large surface area and a suitable pore structure promote mass and electron transfer during the reaction, accelerating the kinetics and progress of methanol oxidation. Furthermore, regulating the catalyst morphology not only effectively enhances the interaction between Pt NPs and the support material, improving the catalytic stability of Pt-based catalysts in methanol oxidation, but also plays a key role in optimizing Pt particle size, dispersion, surface state, exposed crystal faces, number of active sites, and resistance to CO poisoning, thereby influencing the catalytic activity of Pt-based catalysts. Therefore, designing, constructing, and controlling the morphology and structure of Pt-based catalysts is of great significance for improving catalytic performance and exploring the reaction mechanism during methanol oxidation. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for synthesizing a transition metal phosphide Pt-based composite catalyst with controllable morphology.

[0006] The purpose of the present invention is achieved by the following technical solution: a method for synthesizing a transition metal phosphide Pt-based composite catalyst with adjustable morphology, which comprises the following steps:

[0007] S1. Preparation of Fe-DCD precursor: Dissolve ferric nitrate and dicyandiamide in ethanol, heat in a water bath to 70-90°C, and continue stirring until the ethanol is completely evaporated to obtain Fe-DCD precursor.

[0008] S2. Preparation of Fe-Co-DCD precursor: The Fe-DCD precursor prepared in step S1, a surfactant, and cobalt nitrate were dissolved in methanol to form solution A; a methanol solution of dimethylimidazole was slowly added to solution A and mixed uniformly, and then transferred to a reactor at 110 to 130 ° C for 10 to 14 hours to generate a Fe-Co-DCD precursor;

[0009] S3. Preparation of a composite support: The Fe-Co-DCD precursor and triphenylphosphine were mixed and ground uniformly, and calcined at 580-620 ° C under a nitrogen atmosphere for 1.5 to 2.5 h, and then calcined at 780-820 ° C for 1.5 to 2.5 h to obtain a Fe2P-CoP-NDC composite support;

[0010] S4. Preparation of a composite catalyst: The Fe2P-CoP-NDC composite support obtained in step S3 was acid-etched, and after acid etching, Pt nanoparticles were loaded to obtain a Pt / Fe2P-CoP-NDC composite catalyst.

[0011] As a preferred technical solution, the weight ratio of ferric nitrate to dicyandiamide in step S1 is 1:3-5, and the volume ratio of the total mass of ferric nitrate and dicyandiamide to the ethanol solution is 1g:20-30ml.

[0012] As a preferred technical solution, the surfactant in step S2 is any one of cetyltrimethylammonium bromide, polyvinylpyrrolidone or sodium dodecylbenzenesulfonate. If the surfactants are cetyltrimethylammonium bromide, polyvinylpyrrolidone and sodium dodecylbenzenesulfonate, respectively, the morphologies of the prepared Pt / Fe2P-CoP-NDC composite catalyst are hydrangea-shaped, spherical and lamellar, respectively.

[0013] As a preferred technical solution, the weight ratio of the precursor Fe-DCD, surfactant and cobalt nitrate in step S2 is 1:1.5~3:1.2~1.8, the mass volume ratio of dimethylimidazole to methanol solution in the methanol solution of dimethylimidazole is 0.2~0.4g:10ml; the volume ratio of the solution A to the methanol solution of dimethylimidazole is 1.5~3:1.

[0014] As a preferred technical solution, the weight ratio of triphenylphosphine to Fe-DCD in step S3 is 3 to 5:1.

[0015] As a preferred technical solution, the heating rate in step S3 is 1.5-2.5°C / min.

[0016] As a preferred technical solution, the specific operation of the acid etching in step S4 is: the Fe2P-CoP-NDC composite support is immersed in a 0.3-0.8M H2SO4 solution for acid etching for 50-70 minutes.

[0017] As a preferred technical solution, the specific operation steps of loading Pt nanoparticles in step S4 are:

[0018] S41. The Fe2P-CoP-NDC composite support was dispersed in deionized water and uniformly dispersed by ultrasonication, denoted as solution B. The concentration of the Fe2P-CoP-NDC composite support in solution B was 0.8 to 1.2 mg / ml; trisodium citrate and 48.803 mM H2PtCl6-EG (chloroplatinic acid in ethylene glycol) were dissolved in deionized water, denoted as solution C. The concentration of trisodium citrate in solution C was 4 to 6 mg / ml, and the volume ratio of H2PtCl6-EG to deionized water was 1:8 to 12; NaBH4 was dissolved in deionized water, denoted as solution D, and the concentration of NaBH4 in solution D was 0.3 to 0.7 mg / ml;

[0019] S42. While stirring at a speed of 400 to 700 r / min, slowly add solution C to solution B. After mixing evenly, add solution D dropwise. The volume ratio of solution B, solution C and solution D is 3 to 5:1:1.2 to 2. Continue stirring at room temperature for 22 to 26 hours. After the reaction is completed, filter and wash with anhydrous ethanol and deionized water. Then, dry at a temperature of 55 to 65°C for 10 to 14 hours to obtain a transition metal phosphide Pt-based composite catalyst.

[0020] The present invention has the following advantages: The present invention discloses a method for synthesizing a transition metal phosphide Pt-based composite catalyst with controllable morphology. The method of the present invention can produce hydrangea-shaped, spherical, and lamellar Pt / Fe2P-CoP-NDC composite catalysts. Compared to existing granular transition metal phosphide Pt-based composite catalysts, the present invention increases the specific surface area and improves the pore structure, thereby accelerating the reaction kinetics and reaction process of methanol oxidation. Furthermore, by controlling the morphology, the interaction between Pt NPs and the support material can be effectively enhanced, improving the catalytic stability of the Pt-based catalyst in the methanol oxidation reaction. Furthermore, the method plays a key role in optimizing the Pt particle size, dispersion, surface state, exposed crystal planes, number of active sites, and resistance to CO poisoning, thereby enhancing the catalytic activity of the Pt-based catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 XRD patterns of hydrangea-shaped Pt / Fe2P-CoP-NDC (h), spherical Pt / Fe2P-CoP-NDC (s) and lamellar Pt / Fe2P-CoP-NDC (f) composite catalysts.

[0022] Figure 2 This is the SEM image of the lamellar Pt / Fe2P-CoP-NDC catalyst.

[0023] Figure 3 This is the SEM image of the hydrangea-shaped Pt / Fe2P-CoP-NDC catalyst.

[0024] Figure 4 SEM image of spherical Pt / Fe2P-CoP-NDC catalyst.

[0025] Figure 5 CV curves of hydrangea-shaped Pt / Fe2P-CoP-NDC (h), spherical Pt / Fe2P-CoP-NDC (s) and lamellar Pt / Fe2P-CoP-NDC (f) composite catalysts.

[0026] Figure 6Mass activity diagrams of hydrangea-shaped Pt / Fe2P-CoP-NDC (h), spherical Pt / Fe2P-CoP-NDC (s) and lamellar Pt / Fe2P-CoP-NDC (f) composite catalysts.

[0027] Figure 7 The specific activity diagrams of hydrangea-shaped Pt / Fe2P-CoP-NDC (h), spherical Pt / Fe2P-CoP-NDC (s) and lamellar Pt / Fe2P-CoP-NDC (f) composite catalysts.

[0028] Figure 8 CA curves of hydrangea-shaped Pt / Fe2P-CoP-NDC (h), spherical Pt / Fe2P-CoP-NDC (s) and lamellar Pt / Fe2P-CoP-NDC (f) composite catalysts.

[0029] Figure 9 This is a comparison chart of the mass activity of the layered Pt / Fe2P-CoP-NDC(f) catalyst before and after 1000 cycles of testing.

[0030] Figure 10 This is a comparison chart of the mass activity of the hydrangea-shaped Pt / Fe2P-CoP-NDC(h) catalyst before and after 1000 cycles of testing.

[0031] Figure 11 This is a comparison chart of the mass activity of spherical Pt / Fe2P-CoP-NDC(s) catalyst before and after 1000 cycles of testing. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with the accompanying drawings and examples. The scope of protection of the present invention is not limited to the following: Example 1: A method for synthesizing a transition metal phosphide Pt-based composite catalyst with adjustable morphology, comprising the following steps: S1. Preparing a Fe-DCD precursor: dissolving ferric nitrate and dicyandiamide in an ethanol solution, heating and maintaining the solution in a water bath to 70° C., and continuously stirring until the ethanol is completely evaporated to obtain a Fe-DCD precursor; wherein the weight ratio of the ferric nitrate to dicyandiamide is 1:3, and the volume ratio of the total mass of the ferric nitrate and dicyandiamide to the ethanol solution is 1 g:20 ml;

[0033] S2. Preparation of Fe-Co-DCD precursor: The precursor Fe-DCD, hexadecyltrimethylammonium bromide and cobalt nitrate prepared in step S1 were dissolved in methanol to form solution A; a methanol solution of dimethylimidazole was slowly added to solution A and mixed uniformly, and then transferred to a reactor and reacted at 110°C for 10 hours to generate a Fe-Co-DCD precursor;

[0034] The weight ratio of the precursor Fe-DCD, surfactant and cobalt nitrate is 1:1.5:1.2, the mass volume ratio of dimethylimidazole to methanol solution in the dimethylimidazole methanol solution is 0.2g:10ml; the volume ratio of solution A to the dimethylimidazole methanol solution is 1.5:1;

[0035] S3. Preparation of a composite support: After the Fe-Co-DCD precursor and triphenylphosphine were mixed and ground uniformly, the weight ratio of triphenylphosphine to Fe-DCD was 3: 1, and the temperature was increased at a rate of 1.5 ° C / min to 580 ° C and calcined for 1.5 h under a nitrogen atmosphere, and then the temperature was increased at a rate of 1.5 ° C / min to 780 ° C and calcined for 1.5 h to obtain a hydrangea-shaped Fe2P-CoP-NDC composite support;

[0036] S4 Preparation of a composite catalyst: The hydrangea-shaped Fe2P-CoP-NDC composite support obtained in step S3 was immersed in a 0.3M H2SO4 solution and acid-etched for 50 min, and the loaded Pt nanoparticles were loaded after acid etching. The specific steps of the loaded Pt nanoparticles are as follows:

[0037] S41. The hydrangea-shaped Fe2P-CoP-NDC composite carrier was dispersed in deionized water and uniformly dispersed by ultrasonication, denoted as solution B. The concentration of the Fe2P-CoP-NDC composite carrier in solution B was 0.8 mg / ml; trisodium citrate and 48.803 mM H2PtCl6-EG (chloroplatinic acid in ethylene glycol) were dissolved in deionized water, denoted as solution C. The concentration of trisodium citrate in solution C was 4 mg / ml, and the volume ratio of H2PtCl6-EG to deionized water was 1:8; NaBH4 was dissolved in deionized water, denoted as solution D, and the concentration of NaBH4 in solution D was 0.3 mg / ml;

[0038] S42. While stirring at a speed of 400 r / min, solution C was slowly added to solution B. After mixing evenly, solution D was added dropwise. The volume ratio of solution B, solution C and solution D was 3:1:1.2. Stirring was continued at room temperature for 22 hours. After the reaction was completed, the solution was filtered and washed with anhydrous ethanol and deionized water. It was then dried at 55°C for 10 hours to obtain a hydrangea-shaped transition metal phosphide Pt-based composite catalyst.

[0039] Example 2: A method for synthesizing a transition metal phosphide Pt-based composite catalyst with adjustable morphology, comprising the following steps: S1. Preparing a Fe-DCD precursor: dissolving ferric nitrate and dicyandiamide in an ethanol solution, heating the solution to 90°C in a water bath, and continuously stirring the solution until the ethanol is completely evaporated to obtain the Fe-DCD precursor; wherein the weight ratio of the ferric nitrate to dicyandiamide is 1:5, and the volume ratio of the total mass of the ferric nitrate and dicyandiamide to the ethanol solution is 1 g:30 ml;

[0040] S2. Preparation of Fe-Co-DCD precursor: The Fe-DCD precursor prepared in step S1, polyvinyl pyrrolidone and cobalt nitrate were dissolved in methanol to form solution A; the methanol solution of dimethylimidazole was slowly added to solution A and mixed uniformly, and then transferred to a reactor and reacted at 130°C for 14 hours to generate a Fe-Co-DCD precursor;

[0041] The weight ratio of the precursor Fe-DCD, surfactant and cobalt nitrate is 1:3:1.8, the mass volume ratio of dimethylimidazole to methanol solution in the dimethylimidazole methanol solution is 0.4g:10ml; the volume ratio of solution A to the dimethylimidazole methanol solution is 3:1;

[0042] S3. Preparation of a composite support: After the Fe-Co-DCD precursor and triphenylphosphine were mixed and ground uniformly, the weight ratio of triphenylphosphine to Fe-DCD was 5:1, and the mixture was calcined at a heating rate of 2.5 ° C / min to 620 ° C for 2.5 h under a nitrogen atmosphere, and then the temperature was increased at a heating rate of 2.5 ° C / min to 820 ° C and calcined for 2.5 h to obtain a spherical Fe2P-CoP-NDC composite support;

[0043] S4 Preparation of a composite catalyst: The spherical Fe2P-CoP-NDC composite support obtained in step S3 was immersed in a 0.8MH2SO4 solution of acid etching for 70min, and the loaded Pt nanoparticles were loaded after acid etching. The specific steps of the loaded Pt nanoparticles are as follows:

[0044] S41. The spherical Fe2P-CoP-NDC composite support was dispersed in deionized water and uniformly dispersed by ultrasonication, designated as solution B. The concentration of the Fe2P-CoP-NDC composite support in solution B was 1.2 mg / ml; trisodium citrate and 48.803 mM H2PtCl6-EG (chloroplatinic acid in ethylene glycol) were dissolved in deionized water, designated as solution C, the concentration of trisodium citrate in solution C was 6 mg / ml, and the volume ratio of H2PtCl6-EG to deionized water was 1:12; NaBH4 was dissolved in deionized water, designated as solution D, and the concentration of NaBH4 in solution D was 0.7 mg / ml;

[0045] S42. While stirring at a speed of 700 r / min, solution C was slowly added to solution B. After mixing evenly, solution D was added dropwise. The volume ratio of solution B, solution C and solution D was 5:1:2. Stirring was continued at room temperature for 26 hours. After the reaction was completed, the solution was filtered and washed with anhydrous ethanol and deionized water. It was then dried at 65°C for 14 hours to obtain a spherical transition metal phosphide Pt-based composite catalyst.

[0046] Example 3: A method for synthesizing a transition metal phosphide Pt-based composite catalyst with adjustable morphology, comprising the following steps: S1. Preparing a Fe-DCD precursor: dissolving ferric nitrate and dicyandiamide in an ethanol solution, heating the solution to 80°C in a water bath, and continuously stirring the solution until the ethanol is completely evaporated to obtain the Fe-DCD precursor; wherein the weight ratio of the ferric nitrate to dicyandiamide is 1:4, and the volume ratio of the total mass of the ferric nitrate and dicyandiamide to the ethanol solution is 1 g:25 ml;

[0047] S2. Preparation of Fe-Co-DCD precursor: The precursor Fe-DCD, sodium dodecylbenzenesulfonate and cobalt nitrate prepared in step S1 were dissolved in methanol to form solution A; a methanol solution of dimethylimidazole was slowly added to solution A and mixed uniformly, and then transferred to a reactor and reacted at 120°C for 12h to generate a Fe-Co-DCD precursor;

[0048] The weight ratio of the precursor Fe-DCD, surfactant and cobalt nitrate is 1:2:1.5, the mass volume ratio of dimethylimidazole to methanol solution in the dimethylimidazole methanol solution is 0.3g:10ml; the volume ratio of solution A to the dimethylimidazole methanol solution is 2:1;

[0049] S3. Preparation of a composite support: After the Fe-Co-DCD precursor and triphenylphosphine were mixed and ground uniformly, the weight ratio of triphenylphosphine to Fe-DCD was 4:1, and the mixture was calcined at a heating rate of 2°C / min to 600°C for 2h under a nitrogen atmosphere, and then calcined at a heating rate of 2°C / min to 800°C for 2h to obtain a lamellar Fe2P-CoP-NDC composite support;

[0050] S4 preparation of composite catalyst: the lamellar Fe2P-CoP-NDC composite support obtained in step S3 was immersed in 0.5MH2SO4 solution for acid etching for 60min, and the loaded Pt nanoparticles were loaded after acid etching. The specific operation steps of the loaded Pt nanoparticles are as follows:

[0051] S41. The lamellar Fe2P-CoP-NDC composite support was dispersed in deionized water and uniformly dispersed by ultrasonication, denoted as solution B. The concentration of the Fe2P-CoP-NDC composite support in solution B was 1 mg / ml; trisodium citrate and 48.803 mM H2PtCl6-EG (chloroplatinic acid in ethylene glycol) were dissolved in deionized water, denoted as solution C. The concentration of trisodium citrate in solution C was 5 mg / ml, and the volume ratio of H2PtCl6-EG to deionized water was 1:10; NaBH4 was dissolved in deionized water, denoted as solution D, and the concentration of NaBH4 in solution D was 0.5 mg / ml;

[0052] S42. While stirring at a speed of 500 r / min, solution C was slowly added to solution B. After mixing evenly, solution D was added dropwise. The volume ratio of solution B, solution C and solution D was 4:1:1.5. Stirring was continued at room temperature for 24 hours. After the reaction was completed, the solution was filtered and washed with anhydrous ethanol and deionized water. It was then dried at 60°C for 12 hours to obtain a lamellar transition metal phosphide Pt-based composite catalyst.

[0053] The beneficial effects of the present invention are described below by experiments:

[0054] Example 1: A method for synthesizing a transition metal phosphide Pt-based composite catalyst with adjustable morphology, comprising the following steps: S1. Preparing a Fe-DCD precursor: 0.404 g of ferric nitrate and 1.68 g of dicyandiamide were dissolved in 50 mL of ethanol solution, heated in a water bath to 80° C., and stirred continuously until the ethanol was completely evaporated to obtain the Fe-DCD precursor;

[0055] S2. Preparation of Fe-Co-DCD precursor: 0.2 g of the precursor prepared in step S1 Fe-DCD, 0.4g hexadecyltrimethylammonium bromide and 0.3g cobalt nitrate were dissolved in 20mL methanol to form solution A; 0.3g dimethylimidazole was dissolved in 10mL methanol, slowly added to solution A and mixed evenly, then transferred to a 50mL reactor and reacted at 120℃ for 12h. After cooling to room temperature, it was filtered and washed several times with anhydrous ethanol and deionized water, and placed in a 60℃ oven to dry for 12h to generate a Fe-Co-DCD precursor; S3. Preparation of a composite support: The dried Fe-Co-DCD precursor and 0.7g triphenylphosphine were mixed and ground evenly in a quartz mortar, transferred to a porcelain boat, and placed in the middle of a tube furnace. Under a nitrogen atmosphere, the temperature was increased at a rate of 2℃ / min to 600℃ for 2h, and then the temperature was increased at a rate of 2℃ / min to 800℃ for 2h to obtain a Fe2P-CoP-NDC composite support;

[0056] S4 Preparation of composite catalyst: The Fe2P-CoP-NDC composite support was immersed in a 0.5M H2SO4 solution and acid-etched for 60min, and the acid-etched loaded Pt nanoparticles were loaded. The specific steps of the loaded Pt nanoparticles were as follows:

[0057] S41. Accurately weigh 0.02 g of the Fe2P-CoP-NDC composite support and disperse it in 20 mL of deionized water. Ultrasonic dispersion was performed for 20 minutes to achieve uniformity. This was designated Solution B. 0.0245 g of trisodium citrate and 0.525 mL of 48.803 mM H2PtCl6-EG (chloroplatinic acid in ethylene glycol) were dissolved in 5 mL of deionized water. This was designated Solution C. 4.6 mg of NaBH4 was dissolved in 8 mL of deionized water. This was designated Solution D.

[0058] S42. While stirring at a speed of 500 r / min, slowly add solution C to solution B. After mixing evenly, add solution D dropwise and continue stirring at room temperature for 24 hours. After the reaction is completed, filter and wash with anhydrous ethanol and deionized water, and then dry at 60°C for 12 hours to obtain a transition metal phosphide Pt-based composite catalyst.

[0059] Example 2: Same as Example 1, except that the hexadecyltrimethylammonium bromide in step S2 is replaced by polyvinylpyrrolidone. Example 3: Same as Example 1, except that the hexadecyltrimethylammonium bromide in step S2 is replaced by sodium dodecylbenzenesulfonate.

[0060] The transition metal phosphide Pt-based composite catalysts prepared in Example 1, Example 2 and Example 3 were subjected to XRD detection and electron microscope scanning. The results are as follows: Figure 1-Figure 4 As shown, Figure 1 The XRD patterns of the hydrangea-shaped Pt / Fe2P-CoP-NDC (h), spherical Pt / Fe2P-CoP-NDC (s), and lamellar Pt / Fe2P-CoP-NDC (f) composite catalysts are shown. Comparison with the standard chart reveals that, despite some overlap in the diffraction peak positions, the diffraction peaks of the three catalysts still correspond well to the standard peaks of each substance. Furthermore, the XRD patterns of the flake-shaped, hydrangea-shaped, and porous spherical composite catalysts are similar in peak shape, indicating that the three catalysts have the same composition. Figure 2 、 Figure 3 and Figure 4 These are SEM images of three catalysts with different morphologies. It can be seen from the figure that the three catalysts are respectively lamellar, hydrangea-shaped and spherical, proving that the morphology and structure of the catalysts are precisely controlled.

[0061] Figure 5 The CV curves of three catalysts with different morphologies are shown in Figure 2. According to the calculation, the ECSA of the hydrangea-shaped Pt / Fe2P-CoP-NDC (h), spherical Pt / Fe2P-CoP-NDC (s) and lamellar Pt / Fe2P-CoP-NDC (f) composite catalysts are 75.8 m 2 ·g -1 、97.6m 2 ·g -1 and 51.4m 2 ·g -1 . Figure 6 The mass activity and specific activity of three catalysts with different morphologies are shown. The peak current density of spherical Pt / Fe2P-CoP-NDC(s) is 1292 mA·mg -1 Pt , respectively, lamellar Pt / Fe2P-CoP-NDC(f)(508mA·mg -1Pt ), hydrangea-shaped Pt / Fe2P-CoP-NDC(h)(917mA·mg -1 Pt ) composite catalyst current density of 2.54, 1.41 times. And, from Figure 7 The specific activity curves of the three catalysts show that the specific activity of the spherical catalyst is 1.32 mA·cm -2 , which is better than Pt / Fe2P-CoP-NDC(f)(0.99mA·cm -2 ) and Pt / Fe2P-CoP-NDC(h)(1.21mA·cm -2 ) catalyst. At the same time, Figures 8-11 The results of CA test and 1000-cycle cyclic stability test also confirmed that spherical catalysts have better catalytic stability than flake-shaped and hydrangea-shaped catalysts, indicating that the morphology and structure of the catalyst have a key influence on the catalytic performance of the catalyst. Regulating the morphology and structure of Pt-based catalysts is of great significance to the design and development of high-performance composite catalysts.

[0062] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, and they are all covered by the scope of protection of the present invention.

Claims

1. A method for synthesizing a transition metal phosphide Pt-based composite catalyst with adjustable morphology, characterized in that: It includes the following steps: S1. Preparation of Fe-DCD precursor: Dissolve ferric nitrate and dicyandiamide in ethanol. Heat in a water bath to 70-90°C with continuous stirring until the ethanol evaporates completely to prepare the Fe-DCD precursor. S2. Preparation of an Fe-Co-DCD precursor: The Fe-DCD precursor prepared in step S1, a surfactant, and cobalt nitrate are dissolved in methanol to form solution A. A methanol solution of dimethylimidazole is slowly added to solution A and mixed thoroughly. The mixture is then transferred to a reactor and reacted at 110-130°C for 10-14 hours to produce the Fe-Co-DCD precursor. The surfactant is sodium dodecylbenzenesulfonate. S3. Preparation of composite support: Fe-Co-DCD precursor and triphenylphosphine were mixed and ground uniformly, and calcined at 580-620 ° C for 1.5-2.5 h under nitrogen atmosphere, and then calcined at 780-820 ° C for 1.5-2.5 h to obtain Fe2P-CoP-NDC composite support; S4. Preparation of composite catalyst: The Fe2P-CoP-NDC composite support obtained in step S3 was acid-etched, and after acid etching, Pt nanoparticles were loaded to obtain a Pt / Fe2P-CoP-NDC composite catalyst. The morphology of the obtained Pt / Fe2P-CoP-NDC composite catalyst lamellar; The specific operation steps of loading Pt nanoparticles are as follows: S41. The Fe2P-CoP-NDC composite support was dispersed in deionized water and uniformly dispersed by ultrasonication (Solution B). The concentration of the Fe2P-CoP-NDC composite support in Solution B was 0.8-1.2 mg / ml. Trisodium citrate and 48.803 mM H2PtCl6-EG were dissolved in deionized water (Solution C). The concentration of trisodium citrate in Solution C was 4-6 mg / ml, and the volume ratio of H2PtCl6-EG to deionized water was 1:8-12. NaBH4 was dissolved in deionized water (Solution D). The concentration of NaBH4 in Solution D was 0.3-0.7 mg / ml. S42. While stirring at a speed of 400-700 r / min, slowly add solution C to solution B. After mixing evenly, add solution D dropwise. The volume ratio of solution B, solution C and solution D is 3-5:1:1.2-2. Continue stirring at room temperature for 22-26 hours. After the reaction is completed, filter and wash with anhydrous ethanol and deionized water. Then, dry at a temperature of 55-65°C for 10-14 hours to obtain a transition metal phosphide Pt-based composite catalyst.

2. The method for synthesizing a transition metal phosphide Pt-based composite catalyst with adjustable morphology according to claim 1, characterized in that: In step S1, the weight ratio of ferric nitrate to dicyandiamide is 1:3-5, and the volume ratio of the total mass of ferric nitrate and dicyandiamide to the ethanol solution is 1g:20-30ml.

3. The method for synthesizing a transition metal phosphide Pt-based composite catalyst with adjustable morphology according to claim 1, characterized in that: In step S2, the weight ratio of the precursor Fe-DCD, surfactant and cobalt nitrate is 1:1.5~3:1.2~1.8, the mass volume ratio of dimethylimidazole to methanol solution in the dimethylimidazole methanol solution is 0.2~0.4g:10ml; the volume ratio of the solution A to the dimethylimidazole methanol solution is 1.5~3:

1.

4. The method for synthesizing a transition metal phosphide Pt-based composite catalyst with adjustable morphology according to claim 1, characterized in that: The weight ratio of triphenylphosphine to Fe-DCD in step S3 is 3 to 5:

1.

5. The method for synthesizing a transition metal phosphide Pt-based composite catalyst with adjustable morphology according to claim 1, characterized in that: The heating rate in step S3 is 1.5-2.5°C / min.

6. The method for synthesizing a transition metal phosphide Pt-based composite catalyst with adjustable morphology according to claim 1, characterized in that: The specific operation of the acid etching in step S4 is: the Fe2P-CoP-NDC composite support is immersed in a 0.3-0.8M H2SO4 solution and acid-etched for 50-70 minutes.

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