Non-noble metal monatomic carbon material composite Pt alloy electrocatalyst and preparation method and application thereof

Abstract

The invention belongs to the technical field of new energy materials, and discloses a non-noble metal monatomic carbon material composite Pt alloy electrocatalyst and a preparation method and application thereof. The preparation method comprises the following steps: mixing dimethylimidazole and methanol to obtain a solution A; mixing cobalt nitrate hexahydrate, zinc nitrate hexahydrate and methanol to obtain a solution B; mixing polyvinylpyrrolidone with methanol to obtain a solution C; mixing the solution B and the solution C, adding the mixture into the solution A, and sequentially reacting and drying to obtain an organic metal framework compound; carrying out heat treatment on the organic metal framework compound to obtain an N-doped carbon material; mixing the platinum precursor solution and the cobalt precursor solution, adding the N-doped carbon material, and stirring to obtain a catalyst precursor; and carrying out heat treatment on the catalyst precursor to obtain the electrocatalyst. The activity of the obtained catalyst is improved, meanwhile, the use amount of Pt and the cost of the catalyst are remarkably reduced, precious metal resources are saved, and good economic benefits are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy materials, and in particular to an electrocatalyst of a non-noble metal single-atom carbon material composite Pt alloy, and a preparation method and application thereof. Background Art

[0002] Proton exchange membrane fuel cells (PEMFCs) have the advantages of high energy density, simple operation, zero carbon emissions and environmental friendliness. They are widely used in road traffic, aerospace, electronic equipment and backup power supplies.

[0003] As the terminal scenario for green hydrogen energy application, the performance of PEMFC is heavily dependent on catalysts with high Pt loading (>20wt.%) to promote the cathode oxygen reduction reaction (ORR). However, Pt resources are relatively scarce and expensive, resulting in high Pt loading catalysts with high cost.

[0004] The catalyst carrier is an important component of the cathode catalyst, which is used to provide sufficient conductivity and specific surface area to disperse the fine Pt nanoparticles to achieve sufficient electrochemically active surface areas (ECSAs). At present, most Pt-based catalysts are synthesized Pt nanoparticles loaded on commercial carbon powder (Ketjenblack, VulcanXC-72, etc.). However, the Pt nanoparticles loaded on these carbon materials will be thermodynamically unstable due to the weak metal-carrier interaction, causing the PEMFC to migrate, agglomerate or separate under dynamic operating conditions. In particular, during the start-up and shutdown process of the PEMFC, the Pt nanoparticles and the carrier do not interact enough, and the Pt nanoparticles are prone to detach from the carrier, resulting in ECSAs loss and severe performance degradation.

[0005] Therefore, it is of great significance to study and obtain an electrocatalyst composed of non-precious metal single-atom carbon material composite Pt alloy with low Pt loading, long life and strong interaction between Pt nanoparticles and carriers, as well as its preparation method and application. Summary of the invention

[0006] In view of this, the present invention provides an electrocatalyst of a non-precious metal single-atom carbon material composite Pt alloy and a preparation method and application thereof, the purpose of which is to solve the problems of high Pt loading in existing Pt-based catalysts and insufficient interaction between the carrier and Pt nanoparticles.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] The present invention provides a method for preparing an electrocatalyst of a non-noble metal single-atom carbon material composite Pt alloy, comprising the following steps:

[0009] (1) mixing dimethylimidazole and methanol to obtain solution A;

[0010] Mixing cobalt nitrate hexahydrate, zinc nitrate hexahydrate and methanol to obtain solution B;

[0011] Polyvinyl pyrrolidone is mixed with methanol to obtain solution C;

[0012] (2) After mixing solution B and solution C, the mixture is added to solution A, and reacted and dried in sequence to obtain a cobalt-doped organic metal framework compound;

[0013] (3) heat-treating the cobalt-doped organic metal framework compound to obtain an N-doped carbon material containing a single Co atom;

[0014] (4) mixing a platinum precursor solution and a cobalt precursor solution, adding an N-doped carbon material containing a Co single atom, and stirring to obtain a catalyst precursor;

[0015] (5) The catalyst precursor is heat-treated to obtain an electrocatalyst of a non-precious metal single-atom carbon material composite Pt alloy.

[0016] Preferably, in the step (1), the ratio of dimethylimidazole to methanol in solution A is 3-3.5 g:50 mL; the ratio of cobalt nitrate hexahydrate, zinc nitrate hexahydrate to methanol in solution B is 1-1.2 g:2.6-2.7 g:25 mL; and the ratio of polyvinyl pyrrolidone to methanol in solution C is 1-2 g:25 mL.

[0017] Preferably, in the step (1), the mass ratio of dimethylimidazole to polyvinyl pyrrolidone is 3-3.4:1-2, and the mass ratio of dimethylimidazole to cobalt nitrate hexahydrate is 3-3.4:1-1.2.

[0018] Preferably, in step (2), the mixing time is 10 to 15 minutes, the mixing rate is 200 to 400 rpm, the reaction temperature is 50 to 65°C, the reaction time is 25 to 35 minutes, the drying temperature is 55 to 65°C, and the drying time is 20 to 26 hours.

[0019] Preferably, in step (3), the heat treatment is carried out under a protective atmosphere of nitrogen; the heat treatment temperature is 880-940° C., and the heat treatment time is 1-3 h.

[0020] Preferably, in step (4), the platinum precursor in the platinum precursor solution is tetraammineplatinum hydroxide, chloroplatinic acid or platinum acetylacetonate, the solvent in the platinum precursor solution is anhydrous ethanol or water, and the ratio of the platinum precursor to the solvent is 0.0135-0.017 mmol:1.8-2.2 mL; the cobalt precursor in the cobalt precursor solution is cobalt nitrate hexahydrate, cobalt acetylacetonate, cobalt sulfate heptahydrate or cobalt chloride hexahydrate, the solvent in the cobalt precursor solution is anhydrous ethanol or water, and the ratio of the cobalt precursor to the solvent is 0.0045-0.006 mmol:1.8-2.2 mL;

[0021] The usage ratio of the platinum precursor, the cobalt precursor and the N-doped carbon material containing Co single atom is 0.0135-0.017 mmol: 0.0045-0.006 mmol: 50 mg.

[0022] Preferably, in step (4), the mixing is ultrasonic mixing, the power of the ultrasonic mixing is 300-400 W, and the time of the ultrasonic mixing is 25-35 min; the stirring time is 11-13 h, and the stirring speed is 250-350 rpm.

[0023] Preferably, in the step (5), the heat treatment is carried out under a protective atmosphere, the protective atmosphere is a mixture of nitrogen and hydrogen or nitrogen, the volume ratio of nitrogen to hydrogen in the mixture of nitrogen and hydrogen is 75-85:15-25; the heat treatment temperature is 600-800°C, and the heat treatment time is 2-4h.

[0024] The present invention also provides a non-noble metal single-atom carbon material composite Pt alloy electrocatalyst prepared by the preparation method of the non-noble metal single-atom carbon material composite Pt alloy electrocatalyst.

[0025] The present invention also provides the use of the non-noble metal single-atom carbon material composite Pt alloy electrocatalyst in a fuel cell.

[0026] It can be seen from the above technical solutions that, compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention uses nitrogen-doped carbon materials (MNC) dispersed at the transition metal atomic level as carbon carriers, and utilizes its advantages such as good hierarchical pore structure, high surface area, adjustable particle size and rich heterogeneous dopants to make it a carbon carrier for dispersing Pt alloy (PtM) nanoparticles. Pt and transition metal precursors are dispersed on the surface of the material, and PtM is loaded on the surface of the MNC material by heat treatment. On the one hand, during the high-temperature reduction process of the catalyst precursor to prepare PtM alloy nanoparticles, the PtM nanoparticles and the surface of the MNC material produce a strong metal nanoparticle-carrier interaction, which stabilizes the PtM nanoparticles, prevents their migration and agglomeration, and reduces the loss of catalyst activity. On the other hand, compared with traditional carbon carriers, MNC materials as carriers can also provide more MN X Active sites enhance the intrinsic activity of catalysts, PtM ​​nanoparticles and MN X There is a synergistic effect between the sites, which further promotes the improvement of the catalytic performance and durability of the catalyst.

[0028] The electrocatalyst of the non-precious metal single-atom carbon material composite Pt alloy prepared by the present invention has a mass activity 3 to 4 times that of the commercial Pt / C catalyst, and its Pt content can be as low as one-fourth of the commercial Pt / C catalyst. While the catalyst activity is improved, the amount of Pt used is significantly reduced, the cost of the catalyst is effectively reduced, and precious metal resources are saved, which has good economic benefits.

[0029] In the preparation method of the present invention, the raw materials are low in cost and easy to obtain, the preparation process is simple, the equipment requirements are low, and batch production can be carried out at a relatively low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0031] Figure 1 This is the SEM image of Co-NC obtained in Example 1;

[0032] Figure 2 HR-SEM image of Co-NC obtained in Example 1;

[0033] Figure 3 TEM image of a single particle of Co-NC obtained in Example 1;

[0034] Figure 4HADDF-STEM image of Co-NC obtained in Example 1;

[0035] Figure 5 This is a TEM image of the electrocatalyst of the non-noble metal single-atom carbon material composite Pt alloy obtained in Example 1;

[0036] Figure 6 HR-TEM image of the electrocatalyst of the non-noble metal single-atom carbon material composite Pt alloy obtained in Example 1;

[0037] Figure 7 The electrocatalyst of the non-noble metal single-atom carbon material composite Pt alloy obtained in Example 1, the Co-NC obtained in Example 1 and the Pt / C catalyst in O 2 Saturated 1M HClO 4 LSV polarization curve in solution;

[0038] Figure 8 The electrocatalyst of the non-noble metal single-atom carbon material composite Pt alloy obtained in Example 2 and the Pt / C catalyst in O 2 Saturated 1M HClO 4 LSV polarization curve in solution;

[0039] Fig. 9 The electrocatalyst of the non-noble metal single-atom carbon material composite Pt alloy obtained in Example 3 and the Pt / C catalyst in O 2 Saturated 1M HClO 4 LSV polarization curve in solution;

[0040] Fig.10 The electrocatalyst of the non-noble metal single-atom carbon material composite Pt alloy obtained in Example 4 and the Pt / C catalyst in O 2 Saturated 1M HClO 4 LSV polarization curve in solution. DETAILED DESCRIPTION

[0041] The present invention provides a method for preparing an electrocatalyst of a non-noble metal single-atom carbon material composite Pt alloy, comprising the following steps:

[0042] (1) mixing dimethylimidazole and methanol to obtain solution A;

[0043] Mixing cobalt nitrate hexahydrate, zinc nitrate hexahydrate and methanol to obtain solution B;

[0044] Polyvinyl pyrrolidone is mixed with methanol to obtain solution C;

[0045] (2) After mixing solution B and solution C, the mixture is added to solution A, and reacted and dried in sequence to obtain a cobalt-doped organic metal framework compound;

[0046] (3) heat-treating the cobalt-doped organic metal framework compound to obtain an N-doped carbon material containing a single Co atom;

[0047] (4) mixing a platinum precursor solution and a cobalt precursor solution, adding an N-doped carbon material containing a Co single atom, and stirring to obtain a catalyst precursor;

[0048] (5) The catalyst precursor is heat-treated to obtain an electrocatalyst of a non-precious metal single-atom carbon material composite Pt alloy.

[0049] In the present invention, in the step (1), the amount ratio of dimethylimidazole to methanol in solution A is preferably 3-3.5 g:50 mL, more preferably 3.1-3.4 g:50 mL, and more preferably 3.2-3.3 g:50 mL; the amount ratio of cobalt nitrate hexahydrate, zinc nitrate hexahydrate and methanol in solution B is preferably 1-1.2 g:2.6-2.7 g:25 mL, more preferably 1.12-1.18 g:2.62-2.68 g:25 mL, and more preferably 1.14-1.16 g:2.64-2.66 g:25 mL; the amount ratio of polyvinyl pyrrolidone to methanol in solution C is preferably 1-2 g:25 mL, more preferably 1.2-1.8 g:25 mL, and more preferably 1.4-1.6 g:25 mL.

[0050] In the present invention, in the step (1), the mass ratio of dimethylimidazole to polyvinylpyrrolidone is preferably 3-3.4:1-2, more preferably 3.1-3.3:1.2-1.8, more preferably 3.2:1.4-1.6, and the mass ratio of dimethylimidazole to cobalt nitrate hexahydrate is preferably 3-3.4:1-1.2, more preferably 3.1-3.3:1.05-1.15, more preferably 3.2:1.08-1.12.

[0051] In the present invention, in the step (1), the mixing is preferably magnetic stirring, the speed of the magnetic stirring is independently preferably 250 to 350 rpm, and the time of the magnetic stirring is independently preferably 20 to 40 min.

[0052] In the present invention, in the step (2), the mixing time is preferably 10 to 15 min, more preferably 11 to 14 min, more preferably 12 to 13 min, the mixing rate is preferably 200 to 400 rpm, more preferably, the reaction temperature is preferably 50 to 65°C, more preferably 55 to 60°C, more preferably 56 to 58°C, the reaction time is preferably 25 to 35 min, more preferably 28 to 34 min, more preferably 30 to 32 min, the drying temperature is preferably 55 to 65°C, more preferably 58 to 64°C, more preferably 60 to 62°C, and the drying time is preferably 20 to 26 h, more preferably 21 to 25 h, more preferably 22 to 24 h.

[0053] In the present invention, in the step (2), the mixing is preferably magnetic stirring, the reaction is preferably carried out under magnetic stirring, the speed of the magnetic stirring is preferably 250-400 rpm, more preferably 300-350 rpm, more preferably 320-340 rpm; after the reaction, centrifugation, washing, drying and grinding are carried out in sequence, the speed of the centrifugation is preferably 3500-4500 rpm, more preferably 3800-4200 rpm, more preferably 4000-4100 rpm, the centrifugation time is preferably 3-7 min, more preferably 4-6 min, more preferably 5 min, in the washing, the washing reagent is preferably anhydrous ethanol, the number of washings is preferably 2-5 times, more preferably 3-4 times, the drying is preferably vacuum drying, the vacuum drying temperature is preferably 50-70°C, more preferably 55-65°C, more preferably 58-60°C, the grinding time is 20-30 min, more preferably 22-28 min, more preferably 24-26 min.

[0054] In the present invention, in the step (3), the heat treatment is preferably carried out under a protective atmosphere, and the protective atmosphere is preferably nitrogen; the heat treatment temperature is preferably 880-940°C, more preferably 890-930°C, more preferably 900-920°C, and the heat treatment time is preferably 1-3h, more preferably 1.5-2.5h, more preferably 2h.

[0055] In the present invention, in the step (4), the platinum precursor in the platinum precursor solution is preferably tetraamine platinum hydroxide, chloroplatinic acid or platinum acetylacetonate, the solvent in the platinum precursor solution is preferably anhydrous ethanol or water, the water is preferably double distilled water, and the amount ratio of the platinum precursor to the solvent is preferably 0.0135-0.017 mmol: 1.8-2.2 mL, more preferably 0.0145-0.017 mmol: 1.9-2.1 mL, and more preferably 0.015-0.016 mmol: 1.9-2.1 mL. 2.1mL; the cobalt precursor in the cobalt precursor solution is preferably cobalt nitrate hexahydrate, cobalt acetylacetonate, cobalt sulfate heptahydrate or cobalt chloride hexahydrate, the solvent in the cobalt precursor solution is preferably anhydrous ethanol or water, the water is preferably double distilled water, and the amount ratio of the cobalt precursor to the solvent is preferably 0.0045-0.006mmol:1.8-2.2mL, more preferably 0.005-0.0055mmol:1.9-2.1mL, and more preferably 0.0052-0.0054mmol:2mL;

[0056] The usage ratio of platinum precursor, cobalt precursor and N-doped carbon material containing Co single atom is preferably 0.0135-0.017mmol:0.0045-0.006mmol:50mg, more preferably 0.0145-0.017mmol:0.005-0.0055mmol:50mg, and more preferably 0.015-0.016mmol:0.0052-0.0054mmol:50mg.

[0057] In the present invention, in the step (4), the mixing is ultrasonic mixing, the power of the ultrasonic mixing is preferably 300-400 W, more preferably 320-380 W, more preferably 340-350 W, the time of ultrasonic mixing is preferably 25-35 min, more preferably 26-32 min, more preferably 28-30 min, the stirring time is preferably 11-13 h, more preferably 11.5-12.5 h, more preferably 12 h, and the stirring speed is preferably 250-350 rpm, more preferably 280-340 rpm, more preferably 300-320 rpm.

[0058] In the present invention, in the step (4), the stirring is followed by drying; the drying is preferably rotary evaporation drying or freeze drying, the rotary evaporation drying is to rotary evaporate the mixed product and then dry it in vacuum, the rotary evaporation temperature is preferably 60 to 70°C, more preferably 62 to 68°C, more preferably 65 to 66°C, the rotary evaporation time is preferably 12 to 17 min, more preferably 13 to 16 min, more preferably 14 to 15 min, the rotary evaporation speed is preferably 80 to 120 rpm, more preferably 90 to 110 rpm, more preferably 100 rpm, the vacuum drying temperature is preferably 55-65°C, further preferably 56-64°C, more preferably 58-60°C, and the vacuum drying time is preferably 20-25h, further preferably 21-24h, more preferably 22-23h; the freeze-drying temperature is preferably -50--40°C, further preferably -48--42°C, more preferably -45--43°C, and the freeze-drying time is preferably 20-25h, further preferably 21-24h, more preferably 22-23h.

[0059] In the present invention, in the step (5), the heat treatment is preferably carried out under a protective atmosphere, and the protective atmosphere is preferably a mixed gas of nitrogen and hydrogen or nitrogen, and the volume ratio of nitrogen to hydrogen in the mixed gas of nitrogen and hydrogen is preferably 75-85:15-25, more preferably 78-84:16-22, and more preferably 80-82:18-20; the heat treatment temperature is preferably 600-800°C, more preferably 650-750°C, and more preferably 680-700°C. The heat treatment time is preferably 2-4h, more preferably 2.5-3.5h, and more preferably 3h.

[0060] In the present invention, in the step (5), cooling is performed after the heat treatment, and the cooling temperature is preferably 20 to 30°C, more preferably 22 to 28°C, and even more preferably 24 to 26°C.

[0061] The present invention also provides a non-noble metal single-atom carbon material composite Pt alloy electrocatalyst prepared by the preparation method of the non-noble metal single-atom carbon material composite Pt alloy electrocatalyst.

[0062] The present invention also provides the use of the non-noble metal single-atom carbon material composite Pt alloy electrocatalyst in a fuel cell, preferably as a cathode catalyst in a hydrogen-oxygen fuel cell.

[0063] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0064] Example 1

[0065] 3.2 g of dimethylimidazole was added to 50 mL of methanol and magnetically stirred at 300 rpm for 30 min to obtain solution A; 1.16 g of cobalt nitrate hexahydrate and 2.68 g of zinc nitrate hexahydrate were added to 25 mL of methanol and magnetically stirred at 300 rpm for 30 min to obtain a mixed solution B; 1 g of PVP was added to 25 mL of methanol and magnetically stirred at 300 rpm for 30 min to obtain a solution C;

[0066] Then, solution B and solution C were magnetically stirred at 300 rpm for 15 minutes and then added to solution A. After continuous stirring at 60°C for 30 minutes, the mixture was centrifuged at 4000 rpm for 5 minutes. The resulting precipitate was washed three times with anhydrous ethanol and then dried in a vacuum drying oven at 60°C for 24 hours. After drying, the product was ground in a mortar for 25 minutes to obtain a cobalt-doped organic metal framework compound.

[0067] 500 mg of cobalt-doped organic metal framework compound was placed in a quartz boat and transferred into a tube furnace under N 2 Heat treatment at 900 °C for 2 h under atmosphere protection to obtain N-doped carbon material containing Co single atoms, denoted as "Co-NC";

[0068] Take 2 mL of anhydrous ethanol solution of platinum acetylacetonate (concentration of 0.00675 mmol / mL), add it to 2 mL of anhydrous ethanol solution of cobalt acetylacetonate (concentration of 0.00225 mmol / mL), ultrasonicate at a power of 360 W for 30 minutes, add 50 mg of N-doped carbon material containing Co single atom under magnetic stirring at a rate of 300 rpm, ultrasonicate for 30 minutes, continue magnetic stirring at a speed of 300 rpm for 12 hours, then rotary evaporate at a speed of 100 rpm at 65 ° C for 15 minutes, and then vacuum dry at 60 ° C for 24 hours to obtain a catalyst precursor;

[0069] The catalyst precursor was heated in N 2 After heat treatment at 700°C for 2h under atmosphere, the mixture was naturally cooled to 25°C to obtain an electrocatalyst of non-precious metal single-atom carbon material composite Pt alloy.

[0070] Example 2

[0071] 3.2 g of dimethylimidazole was added to 50 mL of methanol and magnetically stirred at 300 rpm for 30 min to obtain solution A; 1.16 g of cobalt nitrate hexahydrate and 2.68 g of zinc nitrate hexahydrate were added to 25 mL of methanol and magnetically stirred at 300 rpm for 30 min to obtain a mixed solution B; 1 g of PVP was added to 25 mL of methanol and magnetically stirred at 300 rpm for 30 min to obtain a solution C;

[0072] Then, solution B and solution C were magnetically stirred at 300 rpm for 10 min and then added to solution A. After continuous stirring at 60°C for 30 min, the mixture was centrifuged at 4000 rpm for 5 min. The resulting precipitate was washed three times with anhydrous ethanol and then dried in a vacuum drying oven at 60°C for 24 h. After drying, the product was ground in a mortar for 25 min to obtain a cobalt-doped organic metal framework compound.

[0073] 500 mg of cobalt-doped organic metal framework compound was placed in a quartz boat and transferred into a tube furnace under N 2 Heat treatment at 900°C for 2h under atmosphere protection to obtain N-doped carbon material containing Co single atoms;

[0074] Take 2 mL of chloroplatinic acid anhydrous ethanol solution (concentration of 0.00675 mmol / mL), add it to 2 mL of acetylacetonate cobalt anhydrous ethanol solution (concentration of 0.00225 mmol / mL), ultrasonicate at a power of 350 W for 30 minutes, add 50 mg of N-doped carbon material containing Co single atom under magnetic stirring at a rate of 300 rpm, ultrasonicate for 30 minutes, continue magnetic stirring at a speed of 300 rpm for 12 hours, then rotary evaporate at a speed of 100 rpm at 65 ° C for 15 minutes, and then vacuum dry at 60 ° C for 24 hours to obtain a catalyst precursor;

[0075] The catalyst precursor was heated in N 2 After heat treatment at 700°C for 2h under atmosphere, the mixture was naturally cooled to 25°C to obtain an electrocatalyst of non-precious metal single-atom carbon material composite Pt alloy.

[0076] Example 3

[0077] 3.2 g of dimethylimidazole was added to 50 mL of methanol and magnetically stirred at 300 rpm for 30 min to obtain solution A; 1.16 g of cobalt nitrate hexahydrate and 2.68 g of zinc nitrate hexahydrate were added to 25 mL of methanol and magnetically stirred at 300 rpm for 30 min to obtain a mixed solution B; 1 g of PVP was added to 25 mL of methanol and magnetically stirred at 300 rpm for 30 min to obtain a solution C;

[0078] Then, solution B and solution C were magnetically stirred at 300 rpm for 10 min and then added to solution A. After continuous stirring at 60°C for 30 min, the mixture was centrifuged at 4000 rpm for 5 min. The resulting precipitate was washed three times with anhydrous ethanol and then dried in a vacuum drying oven at 60°C for 24 h. After drying, the product was ground in a mortar for 25 min to obtain a cobalt-doped organic metal framework compound.

[0079] 500 mg of cobalt-doped organic metal framework compound was placed in a quartz boat and transferred into a tube furnace under N 2 Heat treatment at 900°C for 2h under atmosphere protection to obtain N-doped carbon material containing Co single atoms;

[0080] 50 μL of an aqueous solution of tetraammine platinum hydroxide with a Pt content of 4.5% was added to 2 mL of double distilled water, and ultrasonicated to form a uniform solution, and then added to 2 mL of a hexahydrate aqueous solution of cobalt dichloride (with a concentration of 0.00225 mmol / mL), and ultrasonicated at a power of 400 W for 30 min, and then 50 mg of a N-doped carbon material containing a single Co atom was added under magnetic stirring at a rate of 300 rpm, and after ultrasonicating for 30 min, magnetic stirring was continued at a speed of 300 rpm for 12 h, and then freeze-dried at a temperature of -45 ° C for 24 h to obtain a catalyst precursor;

[0081] The catalyst precursor was heated in N 2 After heat treatment at 700°C for 2h under atmosphere, the mixture was naturally cooled to 25°C to obtain an electrocatalyst of non-precious metal single-atom carbon material composite Pt alloy.

[0082] Example 4

[0083] 3.2 g of dimethylimidazole was added to 50 mL of methanol and magnetically stirred at 300 rpm for 30 min to obtain solution A; 1.16 g of cobalt nitrate hexahydrate and 2.68 g of zinc nitrate hexahydrate were added to 25 mL of methanol and magnetically stirred at 300 rpm for 30 min to obtain a mixed solution B; 1 g of PVP was added to 25 mL of methanol and magnetically stirred at 300 rpm for 30 min to obtain a solution C;

[0084] Then, solution B and solution C were magnetically stirred at 300 rpm for 10 min and then added to solution A. After continuous stirring at 60°C for 30 min, the mixture was centrifuged at 4000 rpm for 5 min. The resulting precipitate was washed three times with anhydrous ethanol and then dried in a vacuum drying oven at 60°C for 24 h. After drying, the product was ground in a mortar for 25 min to obtain a cobalt-doped organic metal framework compound.

[0085] 500 mg of cobalt-doped organic metal framework compound was placed in a quartz boat and transferred into a tube furnace under N 2 Heat treatment at 900°C for 2h under atmosphere protection to obtain N-doped carbon material containing Co single atoms;

[0086] Take 2 mL of anhydrous ethanol solution of platinum acetylacetonate (concentration of 0.00675 mmol / mL), add it to 2 mL of anhydrous ethanol solution of cobalt acetylacetonate (concentration of 0.00225 mmol / mL), ultrasonicate at a power of 360 W for 30 minutes, add 50 mg of N-doped carbon material containing Co single atom under magnetic stirring at a rate of 300 rpm, ultrasonicate for 30 minutes, continue magnetic stirring at a speed of 300 rpm for 12 hours, then rotary evaporate at a speed of 100 rpm at 65 ° C for 15 minutes, and then vacuum dry at 60 ° C for 24 hours to obtain a catalyst precursor;

[0087] The catalyst precursor was heat treated at 600° C. for 2 h in a mixed gas of nitrogen and hydrogen with a volume ratio of 85:15 and then naturally cooled to 25° C. to obtain an electrocatalyst of a non-precious metal single-atom carbon material composite Pt alloy.

[0088] Comparative Example 1

[0089] Commercial Pt / C-JM (20 wt. % Pt) electrocatalyst, denoted as "Pt / C".

[0090] Performance Testing

[0091] The electrochemical performance of the non-noble metal single-atom carbon material composite Pt alloy electrocatalyst obtained in Examples 1 to 4 and the electrocatalyst in Comparative Example 1 were tested as follows to obtain LSV curves:

[0092] Test conditions: Three-electrode system was used in O 2 Saturated 1M HClO 4 In aqueous solution, the rotation speed was 1600 rpm and the scanning rate was 5 mV / s.

[0093] The SEM image of Co-NC obtained in Example 1 is as follows Figure 1 As shown. Figure 1 It can be seen that the electrocatalyst of the non-noble metal single-atom carbon material composite Pt alloy obtained in Example 1 has a unique morphology and uniform size.

[0094] The HR-SEM image of Co-NC obtained in Example 1 is as follows Figure 2 As shown. Figure 2 It can be seen that there are larger metal particles inside the particles, which are larger Co metal particles formed by the aggregation of Co elements during the high-temperature carbonization process.

[0095] The TEM image of a single particle of Co-NC obtained in Example 1 is as follows Figure 3 As shown. Figure 3 It can be seen that the Co element aggregates to form larger Co metal particles embedded in the carbon material matrix.

[0096] The HADDF-STEM image of Co-NC obtained in Example 1 is as follows Figure 4 As shown. Figure 4 It can be seen that a large number of Co single atoms ( Figure 4 The white bright spots in the middle are evenly distributed in the carbon layer on the surface of the catalyst particles, indicating that Co single-atom dispersed carbon material (Co-NC) has been prepared.

[0097] The TEM image of the electrocatalyst of the non-noble metal single-atom carbon material composite Pt alloy obtained in Example 1 is as follows: Figure 5 As shown. Figure 5 It can be seen that in addition to the larger metal particles produced by the aggregation of Co elements when preparing the carbon material, there are also a large number of tiny particles distributed on the surface of the catalyst carbon particles.

[0098] The HR-TEM image of the electrocatalyst of the non-noble metal single-atom carbon material composite Pt alloy obtained in Example 1 is as follows: Figure 6 As shown. Figure 6 It can be seen that the size of the tiny particles is 3 to 5 nm, proving that the Pt and Co precursors are reduced to form small-sized Pt alloy nanoparticles during the secondary pyrolysis.

[0099] The electrocatalyst of the non-noble metal single-atom carbon material composite Pt alloy obtained in Example 1, the Co-NC obtained in Example 1 and the Pt / C catalyst in O 2 Saturated 1M HClO 4 The LSV polarization curve in the solution is shown in Figure 7 As shown. Figure 7 It can be seen that the Co-NC material with Co single atom dispersion is 4 The solution shows good electrochemical activity, and the half-wave potential E 1 / 2 =0.66V, which proves that Co-NC material can provide additional catalytic active sites for Co-NC@PtCo composite catalyst; the electrochemical activity of the electrocatalyst of non-noble metal single-atom carbon material composite Pt alloy obtained in Example 1 is significantly higher than that of Pt / C and Co-NC materials, and its half-wave potential E 1 / 2 It is 25 mV higher than Pt / C and 220 mV higher than Co-NC materials, showing extremely high oxygen reduction activity, and its mass activity at 0.9 V is 3.5 times that of Pt / C.

[0100] The electrocatalyst of the non-noble metal single-atom carbon material composite Pt alloy obtained in Examples 2 to 4 and the Pt / C catalyst in O 2 Saturated 1M HClO 4 The LSV polarization curves in the solution are shown in Figures 8 to 10 As shown. Figures 8 to 10It can be seen that the electrocatalysts of the non-noble metal single-atom carbon material composite Pt alloy obtained in Examples 2 to 4 are 4 It shows good oxygen reduction performance in solution and its activity is higher than that of Pt / C.

[0101] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing an electrocatalyst of a non-noble metal single-atom carbon material composite Pt alloy, characterized in that: The steps include: (1) mixing dimethylimidazole and methanol to obtain solution A; Mixing cobalt nitrate hexahydrate, zinc nitrate hexahydrate and methanol to obtain solution B; Polyvinyl pyrrolidone is mixed with methanol to obtain solution C; (2) After mixing solution B and solution C, the mixture is added to solution A, and reacted and dried in sequence to obtain a cobalt-doped organic metal framework compound; (3) heat-treating the cobalt-doped organic metal framework compound to obtain an N-doped carbon material containing a single Co atom; (4) mixing a platinum precursor solution and a cobalt precursor solution, adding an N-doped carbon material containing a Co single atom, and stirring to obtain a catalyst precursor; (5) The catalyst precursor is heat-treated to obtain an electrocatalyst of a non-precious metal single-atom carbon material composite Pt alloy.

2. The method for preparing a non-noble metal single-atom carbon material composite Pt alloy electrocatalyst according to claim 1, characterized in that: In the step (1), the ratio of dimethylimidazole to methanol in solution A is 3-3.5 g:50 mL; the ratio of cobalt nitrate hexahydrate, zinc nitrate hexahydrate to methanol in solution B is 1-1.2 g:2.6-2.7 g:25 mL; and the ratio of polyvinyl pyrrolidone to methanol in solution C is 1-2 g:25 mL.

3. The method for preparing a non-noble metal single-atom carbon material composite Pt alloy electrocatalyst according to claim 2, characterized in that: In the step (1), the mass ratio of dimethylimidazole to polyvinyl pyrrolidone is 3-3.4:1-2, and the mass ratio of dimethylimidazole to cobalt nitrate hexahydrate is 3-3.4:1-1.

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4. The method for preparing a non-noble metal single-atom carbon material composite Pt alloy electrocatalyst according to claim 1, characterized in that: In the step (2), the mixing time is 10 to 15 minutes, the mixing rate is 200 to 400 rpm, the reaction temperature is 50 to 65° C., the reaction time is 25 to 35 minutes, the drying temperature is 55 to 65° C., and the drying time is 20 to 26 hours.

5. The method for preparing a non-noble metal single-atom carbon material composite Pt alloy electrocatalyst according to claim 2 or 4, characterized in that: In the step (3), the heat treatment is carried out under a protective atmosphere of nitrogen; the heat treatment temperature is 880 to 940° C., and the heat treatment time is 1 to 3 hours.

6. The method for preparing a non-noble metal single-atom carbon material composite Pt alloy electrocatalyst according to claim 5, characterized in that: In the step (4), the platinum precursor in the platinum precursor solution is tetraammineplatinum hydroxide, chloroplatinic acid or platinum acetylacetonate, the solvent in the platinum precursor solution is anhydrous ethanol or water, and the amount ratio of the platinum precursor to the solvent is 0.0135-0.017 mmol:1.8-2.2 mL; the cobalt precursor in the cobalt precursor solution is cobalt nitrate hexahydrate, cobalt acetylacetonate, cobalt sulfate heptahydrate or cobalt chloride hexahydrate, the solvent in the cobalt precursor solution is anhydrous ethanol or water, and the amount ratio of the cobalt precursor to the solvent is 0.0045-0.006 mmol:1.8-2.2 mL; The usage ratio of the platinum precursor, the cobalt precursor and the N-doped carbon material containing Co single atom is 0.0135-0.017 mmol: 0.0045-0.006 mmol: 50 mg.

7. The method for preparing a non-noble metal single-atom carbon material composite Pt alloy electrocatalyst according to claim 6, characterized in that: In the step (4), the mixing is ultrasonic mixing, the power of the ultrasonic mixing is 300 to 400 W, and the time of the ultrasonic mixing is 25 to 35 min; The stirring time is 11 to 13 hours, and the stirring speed is 250 to 350 rpm.

8. The method for preparing a non-noble metal single-atom carbon material composite Pt alloy electrocatalyst according to claim 7, characterized in that: In the step (5), the heat treatment is carried out under a protective atmosphere, wherein the protective atmosphere is a mixture of nitrogen and hydrogen or nitrogen, wherein the volume ratio of nitrogen to hydrogen in the mixture of nitrogen and hydrogen is 75-85:15-25; the heat treatment temperature is 600-800° C., and the heat treatment time is 2-4 hours.

9. The non-noble metal single-atom carbon material composite Pt alloy electrocatalyst obtained by the method for preparing the non-noble metal single-atom carbon material composite Pt alloy electrocatalyst according to any one of claims 1 to 8.

10. Use of the electrocatalyst of the non-noble metal single-atom carbon material composite Pt alloy as claimed in claim 9 in a fuel cell.

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