A nitrogen-carbon nanosphere loaded PtCo alloy catalyst and a preparation method and application thereof

Abstract

This invention provides a nitrogen-carbon nanosphere-supported PtCo alloy catalyst, its preparation method, and its application. The preparation method includes the following steps: Co(NO3)2·6H2O and Zn(NO3)2·6H2O are dispersed in methanol to form solution A, and 2-methylimidazole is dispersed in methanol to form solution B. Solution A is added dropwise to solution B, and the mixture is stirred and reacted at room temperature. After washing and drying, a ZIF-67-ZnCo series precursor is obtained. The ZIF-67-ZnCo series precursor is dispersed in ethanol to form solution C, and H2PtCl6·6H2O is dispersed in deionized water to form solution D. Solution D is added dropwise to solution C, and the mixture is reacted at room temperature. After washing and drying, Pt-ZIF-67-ZnCo is obtained. The Pt-ZIF-67-ZnCo is annealed to obtain the nitrogen-carbon nanosphere-supported PtCo alloy catalyst. This invention enables Zn volatilization and Pt anchoring, and prepares nitrogen-doped carbon nanosphere-supported PtCo alloys. The higher electronegativity of Pt induces electron transfer from Co to Pt, promoting the co-adsorption of H at electron-rich Pt and electron-deficient Co sites. + Together with H2O, it can simultaneously achieve excellent electrocatalytic acidic hydrogen evolution activity and stability.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial synthesis, and more specifically, to a nitrogen-carbon nanosphere-supported PtCo alloy catalyst, its preparation method, and its application. Background Technology

[0002] Energy crises and environmental problems constrain human societal development. Hydrogen energy, renowned for its wide availability, high energy density, and zero pollution, is crucial for building a clean and low-carbon energy system. Water electrolysis is a green hydrogen production technology with zero greenhouse gas emissions, especially proton exchange membrane (PEM) electrolysis, which shows great promise due to its high efficiency, compact structure, and good compatibility with renewable energy sources. However, the highly acidic environment of PEM electrolyzers limits catalyst selection, and reliance on precious metals such as platinum (Pt) and iridium (Ir) increases overall costs. The kinetics of hydrogen evolution at the cathode directly affect hydrogen production efficiency. Therefore, developing low-cost, highly active transition metal-based catalysts to replace commercially available platinum-based materials is essential.

[0003] In recent years, transition metal-based materials such as sulfides, selenides, phosphides, nitrides, carbides, and borides have been used as electrocatalysts for hydrogen evolution, but their activity and stability remain insufficient. Improving hydrogen evolution efficiency fundamentally requires regulating the chemical composition and electronic structure of the catalyst to optimize surface charge distribution and achieve optimal adsorption / desorption of hydrogen-containing intermediates. Single-component catalysts have a fixed H binding energy, and introducing different components can regulate the efficiency through synergistic effects. * H2 adsorption / desorption behavior and optimized reaction kinetics are key areas of focus. Hybrid catalysts, such as those supporting metal nanoparticles on nitrogen-doped carbon (M / NC), combine the high conductivity of graphite carbon, the electron-donating capacity of nitrogen, and the intrinsic catalytic activity of dispersed metal sites, making them a promising alternative. Furthermore, alloy catalysts can balance atomic-level interactions between metal sites, improving mass transfer, intermediate bonding, and electron transfer. Currently, nitrogen-doped carbon / cobalt composites (Co / NC) are widely used in acidic hydrogen evolution due to their strong redox properties and oxygen affinity; however, their slow charge transfer kinetics limit their application in acidic hydrogen evolution.

[0004] Studies have shown that cobalt-based alloy MCo / NC catalysts exhibit good potential in acidic hydrogen evolution. However, traditional nitrogen-doped carbon supports have insufficient anchoring ability for MCo nanoparticles, leading to particle agglomeration during pyrolysis nucleation and reduced utilization of active sites. Summary of the Invention

[0005] In view of this, the present invention aims to propose a nitrogen-carbon nanosphere supported PtCo alloy catalyst, its preparation method and application, in order to solve the problems of low hydrogen evolution activity, poor acidic hydrogen evolution performance and low utilization of active sites in the prior art.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0007] A method for preparing a PtCo alloy catalyst supported on nitrogen-carbon nanospheres includes the following steps:

[0008] Step 1: Disperse Co(NO3)2·6H2O and Zn(NO3)2·6H2O in methanol and stir until homogeneous to form solution A. Disperse 2-methylimidazole in methanol and stir until homogeneous to form solution B. Add solution A dropwise to solution B, stir, and react at room temperature. After washing and drying, obtain ZIF-67-ZnCo series precursors.

[0009] Step 2: Disperse the prepared ZIF-67-ZnCo series precursor in ethanol and stir until homogeneous to form solution C. Disperse H2PtCl6·6H2O in deionized water and stir until homogeneous to form solution D. Add solution D dropwise to solution C. After reacting at room temperature, wash and dry to obtain Pt-ZIF-67-ZnCo.

[0010] Step 3: The prepared Pt-ZIF-67-ZnCo was annealed to obtain a nitrogen-carbon nanosphere-supported PtCo alloy catalyst.

[0011] Optionally, in step one, the molar ratio of the inorganic metal source formed by Co(NO3)2·6H2O and Zn(NO3)2·6H2O to 2-methylimidazole is 1:(6~10).

[0012] Optionally, in step one, the molar ratio of Co(NO3)2·6H2O to Zn(NO3)2·6H2O is (1~16):1.

[0013] Optionally, in step one, the reaction is carried out at room temperature for 22-26 hours.

[0014] Optionally, in step two, the molar ratio of added H2PtCl6·6H2O to Co(NO3)2·6H2O is 1:(125~235).

[0015] Optionally, in step three, the annealing conditions are as follows: using high-purity argon as the annealing atmosphere, an annealing temperature of 950~980℃, and an annealing time of 2~3 hours.

[0016] Optionally, in step one, the molar ratio of Co(NO3)2·6H2O to Zn(NO3)2·6H2O is 4:1.

[0017] The present invention also proposes a nitrogen-carbon nanosphere supported PtCo alloy catalyst, which is prepared by the above-mentioned method for preparing nitrogen-carbon nanosphere supported PtCo alloy catalyst.

[0018] Optionally, the nitrogen-carbon nanosphere-supported PtCo alloy catalyst has a nitrogen-doped carbon nanotube dodecahedron-supported metal nanoparticle morphology.

[0019] This invention also proposes the application of the above-mentioned nitrogen-carbon nanosphere-supported PtCo alloy catalyst in electrocatalytic acidic hydrogen evolution.

[0020] Compared with existing technologies, the nitrogen-carbon nanosphere-supported PtCo alloy catalyst, its preparation method, and its application described in this invention have the following advantages:

[0021] (1) In this invention, 2-methylimidazole is used as an organic ligand, and Co-containing and Zn-containing compounds are used as inorganic metal sources. ZnCo MOFs are first synthesized, and then ZnCo MOFs are used as templates to synthesize ZnCo MOFs by means of PtCl6. 2- Ion exchange and subsequent inert gas annealing treatment enable Zn volatilization and Pt anchoring to prepare nitrogen-doped carbon nanosphere-supported PtCo alloys (PtCo / NC-ZnCo). This method has the advantages of low raw material cost and easy availability, and the preparation process is mild, simple, and has no adverse environmental impact.

[0022] (2) PtCl6 is selected in this invention. 2- During ion exchange, the larger Pt atoms cause a downshift in X-ray diffraction peaks, increase interplanar spacing, and generate lattice defects, which can promote the capture of reaction intermediates. Furthermore, the higher electronegativity of Pt induces electron transfer from Co to Pt, modulates the electronic structure of the two-site system, and promotes the synergistic adsorption of H by electron-rich Pt and electron-deficient Co sites. + Together with H2O, it can simultaneously achieve excellent electrocatalytic acidic hydrogen evolution activity and stability.

[0023] (3) By adjusting the Zn / Co ratio in the ZnCo MOF template, the composition and structure of the catalyst can be controlled, thereby improving the acidic hydrogen evolution performance. Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0025] Figure 1 Transmission electron microscope image of the ZIF-67-Zn1Co4 precursor of the zeolite imidazole ester skeleton prepared in Example 1;

[0026] Figure 2 Transmission electron microscope image of the Pt-ZIF-67-Zn1Co4 precursor prepared in Example 1;

[0027] Figure 3 a is a transmission electron microscope image of the PtCo / NC-Zn1Co4 nanomaterials prepared in Example 1; Figure 3 b is the corresponding high-resolution transmission electron microscope image;

[0028] Figure 4 a is a transmission electron microscope image of the Co / NC-Zn1Co4 nanomaterial prepared in Comparative Example 1. Figure 4 b is a high-resolution transmission electron microscope image;

[0029] Figure 5 Selected area electron diffraction image of PtCo / NC-Zn1Co4 nanomaterials derived from the zeolite imidazole ester framework prepared in Example 1;

[0030] Figure 6 a is the elemental distribution diagram of the PtCo / NC-Zn1Co4 nanomaterials prepared in Example 1. Figure 6 b represents the corresponding EDS spectrum;

[0031] Figure 7 Inductively coupled plasma spectra of PtCo / NC-Zn1Co4 prepared in Example 1 and Co / NC-Zn1Co4 prepared in Comparative Example 1;

[0032] Figure 8 PtCo / NC-Zn zeolite imidazole ester-derived zeolite was prepared in Example 2. 2.5 Co 2.5 Transmission electron microscope images of nanomaterials;

[0033] Figure 9 PtCo / NC-Zn zeolite imidazole ester-derived zeolite was prepared in Example 3. 0.3 Co 4.7 Transmission electron microscope images of nanomaterials;

[0034] Figure 10 X-ray diffraction patterns of the ZIF-67-Zn1Co4 precursor prepared in Example 1 and the Pt-ZIF-67-ZnCo series precursors prepared in Examples 1-3, where the horizontal axis represents degrees and the vertical axis represents intensity.

[0035] Figure 11 The X-ray diffraction patterns of PtCo / NC-ZnCo prepared in Examples 1-3 and Co / NC-Zn1Co4 prepared in Comparative Example 1 are shown, where the horizontal axis represents degrees and the vertical axis represents intensity.

[0036] Figure 12Raman spectra of PtCo / NC-ZnCo prepared in Examples 1-3 and Co / NC-Zn1Co4 prepared in Comparative Example 1; where the horizontal axis represents Raman shift and the vertical axis represents intensity.

[0037] Figure 13 a represents the N2 isothermal adsorption / desorption curves of PtCo / NC-Zn1Co4 prepared in Example 1 and Co / NC-Zn1Co4 prepared in Comparative Example 1 at 77K, where the horizontal axis represents relative pressure / P / P0 and the vertical axis represents adsorption amount. Figure 13 b is the corresponding pore size distribution diagram, where the horizontal axis represents the pore size and the vertical axis represents the pore volume;

[0038] Figure 14 a shows the XPS total spectra of PtCo / NC-ZnCo prepared in Examples 1-3 and Co / NC-Zn1Co4 prepared in Comparative Example 1. Figure 14 b is the corresponding Co 2p spectrum. Figure 14 c is the corresponding Pt 4f spectrum. Figure 14 d is the high-resolution energy spectrum of the corresponding N 1s orbital;

[0039] Figure 15 a is a linear voltammetry curve, where the horizontal axis is the standard hydrogen electrode potential using Ag / AgCl reference electrode, and the vertical axis is the current density; Figure 15 b is the Tafel curve, where the horizontal axis is the logarithm of the current density and the vertical axis is the electrode potential; Figure 15 c is the double-layer capacitance fitting curve, where the horizontal axis is the scan rate and the vertical axis is the current density. Figure 15 d is the AC impedance diagram, and the inset diagram is the equivalent circuit diagram; Figure 15 e represents a comparison of the switching frequencies at -0.071V vs. RHE potential; Figure 15 f is a schematic diagram summarizing the acidic hydrogen evolution performance; Figure 15 g is at 0.1A cm -2 Vt curves of PtCo / NC-Zn1Co4 electrolysis for 100h, where the horizontal axis is time and the vertical axis is electrode potential;

[0040] Figure 16 a represents the LSV curve of PtCo / NC-Zn1Co4‖RuO2, where the horizontal axis represents the cell voltage and the vertical axis represents the current. Figure 16 b represents the membrane electrode at 0.1 A cm⁻¹ -2 The Vt curve is shown below, where the horizontal axis represents time and the vertical axis represents the tank pressure. Detailed Implementation

[0041] The present invention will be further described below with reference to specific embodiments. First, it should be noted that the data in the following experimental examples were obtained by the inventors through numerous experiments. Due to space limitations, only a portion of these data is shown in the specification, and those skilled in the art can understand and implement the present invention based on this data. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various modifications or alterations to the invention, and these modifications or alterations also fall within the scope of protection of this application.

[0042] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0043] The preparation method of a nitrogen-carbon nanosphere-supported PtCo alloy catalyst proposed in this invention includes the following steps:

[0044] Step 1: Disperse Co(NO3)2·6H2O and Zn(NO3)2·6H2O in methanol and stir until homogeneous to form solution A. Disperse 2-methylimidazole in methanol and stir until homogeneous to form solution B. Add solution A dropwise to solution B, stir, and react at room temperature. After washing and drying, obtain ZIF-67-ZnCo series precursors.

[0045] Step 2: Disperse the prepared ZIF-67-ZnCo series precursor in ethanol and stir until homogeneous to form solution C. Disperse H2PtCl6·6H2O in deionized water and stir until homogeneous to form solution D. Add solution D dropwise to solution C. After reacting at room temperature, wash and dry to obtain Pt-ZIF-67-ZnCo.

[0046] Step 3: The prepared Pt-ZIF-67-ZnCo was annealed to obtain a nitrogen-carbon nanosphere-supported PtCo alloy catalyst.

[0047] In step one, the molar ratio of the inorganic metal source formed by Co(NO3)2·6H2O and Zn(NO3)2·6H2O to 2-methylimidazole is 1:(6~10), and the molar ratio of Co(NO3)2·6H2O to Zn(NO3)2·6H2O is (1~16):1.

[0048] In step one, the reaction is carried out at room temperature for 22-26 hours.

[0049] In step two, the molar ratio of added H2PtCl6·6H2O to Co(NO3)2·6H2O is 1:(125~235).

[0050] In step three, the annealing conditions are as follows: high-purity argon is used as the annealing atmosphere, the annealing temperature is 950~980℃, and the annealing time is 2~3 hours. Specifically, the purity of the argon is 99.99%.

[0051] This invention uses 2-methylimidazole as an organic ligand and Co-containing and Zn-containing compounds as inorganic metal sources to first synthesize ZnCo MOFs. Then, using the ZnCo MOFs as templates, PtCl6 is used to synthesize... 2- Ion exchange and subsequent inert gas annealing treatment enable Zn volatilization and Pt anchoring to prepare nitrogen-doped carbon nanosphere-supported PtCo alloys (PtCo / NC-ZnCo). This method has the advantages of low raw material cost and easy availability, and the preparation process is mild, simple, and has no adverse environmental impact.

[0052] This invention uses PtCl6 2- During ion exchange, the larger Pt atoms cause a downshift in X-ray diffraction peaks, increase interplanar spacing, and generate lattice defects, which can promote the capture of reaction intermediates. Furthermore, the higher electronegativity of Pt induces electron transfer from Co to Pt, modulates the electronic structure of the two-site system, and promotes the synergistic adsorption of H by electron-rich Pt and electron-deficient Co sites. + and H2

[0053] In particular, only a 19mV overpotential is required to reach 0.01A cm⁻¹ in PtCo / NC-Zn1Co₄ 0.5M H₂SO₄. -2 The current density, and the PtCo / NC-Zn1Co4‖RuO2 film electrode was driven at 1.94V for 0.1A cm⁻¹ in a PEM electrolyzer. -2 It boasts high current density and stability exceeding 100 hours, demonstrating its potential for practical applications.

[0054] The use of H2PtCl6·6H2O in this invention is for the following reasons: First, the rate-determining step of acidic HER is usually H2PtCl6·6H2O. + The adsorption / reduction or desorption of H2 by Pt. The central position of the d-band of Pt makes it suitable for hydrogen intermediates ( * The adsorption of H by Pt is neither too strong nor too weak, thus exhibiting the highest intrinsic activity—a theoretical advantage unmatched by any other noble metal. Secondly, the alloying of Pt and Co produces a strong electron synergistic effect. With electronegativity Pt (2.28) > Co (1.88), electrons transfer from Co to Pt, forming electron-rich Pt and electron-deficient Co. This charge polarization promotes the adsorption of H by Pt. +Co adsorbs H2O, achieving "dual-function" synergistic catalysis and significantly reducing overpotential. If other metal sources are selected, such as Ir (electronegativity 2.20), its electronegativity difference with Co is small, resulting in weak electron transfer; for example, Ru (electronegativity 2.20), although Ru and Co can alloy, the H binding energy in Ru's acidic HER is slightly stronger, making it prone to poisoning; Au (2.54) has a higher electronegativity, but Au itself has too weak an H adsorption capacity, and after alloying, it may excessively deprive Co of electrons, which is not conducive to H2O activation. Third, Pt has a large atomic radius, which can induce lattice strain and defects. The atomic radius of Pt (139 pm) is greater than that of Co (125 pm), and its introduction leads to the expansion of the Co lattice and an increase in the interplanar spacing, resulting in tensile strain. This strain optimizes the d-band structure of Co sites and weakens the effect on the lattice. * Excessive adsorption of H. If smaller Ru (134 pm) or smaller Ir (136 pm) is used, the strain effect is not obvious; if larger Au (144 pm) is used, excessive strain may lead to lattice mismatch and phase separation.

[0055] Existing technologies often involve calcining MOF materials before loading, while in this invention, ZnCo MOFs are directly loaded with PtCl6 without calcination. 2- Ion exchange followed by annealing. The uncalcined MOFs retained their complete dodecahedral morphology, ordered pore structure, and uniformly distributed Co. 2+ / Zn 2+ Metal node. PtCl6 2- Pt can be uniformly anchored on the surface and within the pores of MOFs through ion exchange, thus forming uniformly loaded small-sized PtCo alloy nanoparticles after subsequent annealing. If calcined first, MOFs will carbonize into a disordered nitrogen-doped carbon framework, and the metal nodes tend to agglomerate into larger Co particles. In this case, Pt loading can only occur on the particle surface, failing to achieve atomic-level PtCo alloying, resulting in low Pt utilization and weak alloying effect. Furthermore, in uncooked ZnCo MOFs, Zn... 2+ The Zn atoms are uniformly distributed within the framework. During high-temperature annealing, Zn volatilizes, leaving Zn vacancies. These vacancies are beneficial for capturing Pt atoms and forming a PtCo alloy, while also generating lattice strain and defect sites, thus enhancing catalytic activity. If calcination is performed first, the Zn has already volatilized during the first high-temperature treatment, and the Zn vacancies in the formed Co / NC structure will be covered or collapsed by the carbon layer. Therefore, when Pt is loaded, the Zn vacancies cannot be used to regulate the alloy structure.

[0056] Example 1

[0057] (1) Preparation of ZIF-67-Zn1Co4: 4 mmol (1.16 g) of Co(NO3)2·6H2O and 1 mmol (297.49 mg) of Zn(NO3)2·6H2O were dispersed in 100 mL of methanol and stirred to form a homogeneous solution A. 40 mmol (3.28 g) of 2-methylimidazole was dispersed in 100 mL of methanol and stirred to form a homogeneous solution B. Solution A was added dropwise to solution B, and the mixture was stirred vigorously at 500 rpm for 5 min at room temperature (approximately 25 °C), and then allowed to stand at 25 °C for 24 h. The obtained purple product was centrifuged several times with methanol and then dried overnight under vacuum at 60 °C. The obtained precursor was named ZIF-67-Zn1Co4.

[0058] (2) Preparation of Pt-ZIF-67-Zn1Co4: 50 mg ZIF-67-Zn1Co4 was dispersed in 10 ml of ethanol and stirred vigorously at 500 rpm for 10 min at 25 °C to form a homogeneous solution C. 0.02 mmol (10 mg) H2PtCl6·6H2O was dispersed in 10 ml of deionized water and stirred vigorously at 500 rpm for 10 min at 25 °C to form a homogeneous solution D. Solution D was added dropwise to solution C, and the mixture was stirred at 25 °C for 2 h. The product was centrifuged several times with deionized water and ethanol, and then dried overnight under vacuum at 60 °C. The obtained precursor was named Pt-ZIF-67-Zn1Co4.

[0059] (3) Preparation of PtCo / NC-Zn1Co4: 100 mg of Pt-ZIF-67-Zn1Co4 precursor was placed in a porcelain boat, transferred to a tube furnace, and then incubated at 5 °C for 1 min. -1 The heating rate was increased to 950 °C and maintained under an argon atmosphere for 2 hours. After natural cooling to room temperature under an argon atmosphere, the resulting product was named PtCo / NC-Zn1Co4.

[0060] Example 2

[0061] (1) ZIF-67-Zn 2.5 Co 2.5 Preparation: 2.5 mmol (727.58 mg) Co(NO3)2·6H2O and 2.5 mmol (743.71 mg) Zn(NO3)2·6H2O were dispersed in 100 mL of methanol and stirred to form a homogeneous solution A. 40 mmol (3.28 g) 2-methylimidazole was dispersed in 100 mL of methanol and stirred to form a homogeneous solution B. Solution A was added dropwise to solution B, and the mixture was vigorously stirred at 500 rpm for 5 min at room temperature (approximately 25 °C), then allowed to stand at 25 °C for 24 h. The obtained purple product was centrifuged several times with methanol and then dried overnight under vacuum at 60 °C. The obtained precursor was named ZIF-67-Zn. 2.5Co 2.5 .

[0062] (2) Pt-ZIF-67-Zn 2.5 Co 2.5 Preparation: 50 mg ZIF-67-Zn 2.5 Co 2.5 Disperse the product in 10 ml of ethanol and stir vigorously at 500 rpm for 10 min at 25 °C to form a homogeneous solution C. Disperse 0.02 mmol (10 mg) of H₂PtCl₆·6H₂O in 10 ml of deionized water and stir vigorously at 500 rpm for 10 min at 25 °C to form a homogeneous solution D. Add solution D dropwise to solution C, and then stir the mixture at 25 °C for 2 h. Centrifuge the product several times with deionized water and ethanol, and then dry it overnight under vacuum at 60 °C. The obtained precursor is named Pt-ZIF-67-Zn. 2.5 Co 2.5 .

[0063] (3) PtCo / NC-Zn 2.5 Co 2.5 Preparation: 100 mg of Pt-ZIF-67-Zn 2.5 Co 2.5 The precursor was placed in a porcelain boat and transferred to a tube furnace, then heated at 5°C for 1 minute. -1 The heating rate was increased to 950 °C and maintained under an argon atmosphere for 2 hours. After natural cooling to room temperature under an argon atmosphere, the resulting product was named PtCo / NC-Zn. 2.5 Co 2.5 .

[0064] Example 3

[0065] (1) ZIF-67-Zn 0.3 Co 4.7 Preparation: 4.7 mmol (1.37 g) Co(NO3)2·6H2O and 0.3 mmol (89.24 mg) Zn(NO3)2·6H2O were dispersed in 100 mL of methanol and stirred to form a homogeneous solution A. 40 mmol (3.28 g) 2-methylimidazole was dispersed in 100 mL of methanol and stirred to form a homogeneous solution B. Solution A was added dropwise to solution B, and the mixture was vigorously stirred at 500 rpm for 5 min at room temperature (approximately 25 °C), then allowed to stand at 25 °C for 24 h. The purple product was centrifuged several times with methanol and then dried overnight under vacuum at 60 °C. The obtained precursor was named ZIF-67-Zn. 0.3 Co 4.7 .

[0066] (2) Pt-ZIF-67-Zn 0.3 Co 4.7Preparation: 50 mg ZIF-67-Zn 0.3 Co 4.7 Disperse the product in 10 ml of ethanol and stir vigorously at 500 rpm for 10 min at 25 °C to form a homogeneous solution C. Disperse 0.02 mmol (10 mg) of H₂PtCl₆·6H₂O in 10 ml of deionized water and stir vigorously at 500 rpm for 10 min at 25 °C to form a homogeneous solution D. Add solution D dropwise to solution C, and then stir the mixture at 25 °C for 2 h. Centrifuge the product several times with deionized water and ethanol, and then dry it overnight under vacuum at 60 °C. The obtained precursor is named Pt-ZIF-67-Zn. 0.3 Co 4.7 .

[0067] (3) PtCo / NC-Zn 0.3 Co 4.7 Preparation: 100 mg of Pt-ZIF-67-Zn 0.3 Co 4.7 The precursor was placed in a porcelain boat and transferred to a tube furnace, then heated at 5°C for 1 minute. -1 The heating rate was increased to 980 °C and maintained under an argon atmosphere for 2 hours. After natural cooling to room temperature under an argon atmosphere, the resulting product was named PtCo / NC-Zn. 0.3 Co 4.7 .

[0068] Comparative Example 1

[0069] Preparation of ZIF-67-Zn1Co4: 4 mmol (1.16 g) of Co(NO3)2·6H2O and 1 mmol (297.49 mg) of Zn(NO3)2·6H2O were dispersed in 100 mL of methanol and stirred to form a homogeneous solution A. 40 mmol (3.28 g) of 2-methylimidazole was dispersed in 100 mL of methanol and stirred to form a homogeneous solution B. Solution A was added dropwise to solution B, and the mixture was vigorously stirred at 500 rpm for 5 min at room temperature (approximately 25 °C), followed by standing at 25 °C for 24 h. The obtained purple product was centrifuged several times with methanol and then dried overnight under vacuum at 60 °C. The obtained precursor was named ZIF-67-Zn1Co4.

[0070] 100 mg of ZIF-67-Zn1Co4 precursor was placed in a ceramic boat, transferred to a tube furnace, and then incubated at 5 °C for 1 minute. -1 The heating rate was increased to 950 °C and maintained under an argon atmosphere for 2 hours. After natural cooling to room temperature under an argon atmosphere, the resulting product was named Co / NC-Zn1Co4.

[0071] The products obtained from each step of Examples 1, 2, and 3, as well as the final product prepared in Comparative Example 1, were characterized and tested.

[0072] like Figure 1 As shown, the zeolite imidazole ester framework ZIF-67-Zn1Co4 precursor prepared in Example 1 exhibits a smooth dodecahedral morphology (approximately 100 nm). Figure 2 As shown, the Pt-ZIF-67-Zn1Co4 formed after the introduction of Pt retains its polyhedral structure, but its surface roughness increases. A transmission electron microscope image of the imidazole ester-derived PtCo / NC-Zn1Co4 nanomaterial obtained in Example 1 is shown below. Figure 3 As shown in Figure a, after annealing, the material transforms into nitrogen-doped carbon nanotubes supported by metal nanoparticles with a size of approximately 100 nm. The fully exposed metal sites are beneficial for electrocatalytic reactions. A high-resolution transmission electron microscope image of the PtCo / NC-Zn1Co4 nanomaterial obtained in Example 1 is shown below. Figure 3 As shown in b, lattice spacings of 0.178 and 0.204 (0.206) nm are exposed, corresponding to the (200) and (111) crystal planes of Co, and lattice defects with Zn vacancies are present.

[0073] like Figure 4 a and 4b are transmission electron microscope (TEM) images and high-resolution TEM images of Co / NC-Zn1Co4 prepared in Comparative Example 1, respectively. Compared with PtCo / NC-Zn1Co4 in Example 1, Comparative Example 1 shows an aggregated morphology of Co nanoparticles, and only lattice spacings of 0.125 nm, 0.177 nm, and 0.204 nm can be measured, corresponding to the (220), (200), and (111) crystal planes of elemental Co, respectively.

[0074] PtCo / NC-Zn prepared in Example 2 2.5 Co 2.5 PtCo / NC-Zn prepared in Example 3 0.3 Co 4.7 Nanomorphological features are as follows Figure 8 , Figure 9 As shown, both exhibit the same nanosphere morphology with the same particle size.

[0075] Selected area electron diffraction (SED) images of the PtCo / NC-Zn1Co4 nanomaterials prepared in Example 1 are shown below. Figure 5 As shown, the SAED pattern only shows diffraction rings belonging to metallic Co, with no evidence of Pt phase segregation.

[0076] The elemental distribution diagram of the PtCo / NC-Zn1Co4 nanomaterials prepared in Example 1 is shown below. Figure 6 As shown in a, the EDS spectrum is as follows: Figure 6 As shown in b, due to the volatilization of Zn during high-temperature annealing and the Pt:Co atomic ratio of 1:145, Zn is absent, indicating only the interaction between Pt and Co exists. The simultaneous presence of N and C indicates that the nitrogen-containing ligand is transformed into a nitrogen-doped carbon support. Combined with... Figure 6 a. All elements are uniformly distributed, with Pt and Co exhibiting an overlapping spatial distribution, which is consistent with the formation of the alloy structure.

[0077] The inductively coupled plasma spectra of PtCo / NC-Zn1Co4 prepared in Example 1 and Co / NC-Zn1Co4 prepared in Comparative Example 1 are shown below. Figure 7 As shown, neither contains Zn, and Example 1 has a higher Pt:Co ratio (1:118), indicating that the PtCo alloy is distributed both on the surface and in the bulk phase.

[0078] The X-ray diffraction patterns of the ZIF-67-Zn1Co4 precursor prepared in Example 1 and the Pt-ZIF-67-ZnCo series precursors prepared in Examples 1-3 are as follows: Figure 10 As shown, all characteristic peaks are aligned with the simulated ZIF-67, confirming the formation of Zn-doped Co-based MOFs. The X-ray diffraction peaks of the precursor did not change after the introduction of Pt, indicating that PtCl6... 2- Electrostatic adsorption occurred in the absence of chemical bonds.

[0079] The X-ray diffraction patterns of PtCo / NC-ZnCo prepared in Examples 1-3 and Co / NC-Zn1Co4 prepared in Comparative Example 1 are as follows: Figure 11 As shown. The annealed products of Examples 1-3 all exhibit diffraction peaks at 44.22° and 51.53°, corresponding to the metal Co (JCPDS No. 89-4307), indicating that Zn volatilized at high temperatures. Comparative Example 1 shows similar peak positions but with reduced intensity, indicating no new phase formation on the surface. The slight low-angle shift observed in Examples 1-3 is attributed to lattice expansion caused by Pt atom doping.

[0080] The Raman spectra of PtCo / NC-ZnCo prepared in Examples 1-3 and Co / NC-Zn1Co4 prepared in Comparative Example 1 are as follows: Figure 12 As shown. Example 1 exhibits the highest I. D / I G The comparison indicates that the introduction and volatilization of an appropriate amount of Zn will generate a large number of carbon defects, which is beneficial for the adsorption of reactant species and enhances electrocatalytic activity.

[0081] The N2 isothermal adsorption / desorption measurement curves of PtCo / NC-Zn1Co4 prepared in Example 1 and Co / NC-Zn1Co4 prepared in Comparative Example 1 at 77 K are shown below. Figure 13As shown in Figure a, the pore size distribution diagram is as follows: Figure 13 As shown in b, the specific surface area of ​​PtCo / NC-Zn1Co4 is 140.58 m². 2 g -1 It is lower than the 241.39m of Co / NC-Zn1Co4. 2 g -1 The reduction in specific surface area and average pore size (2.08 nm) of PtCo / NC-Zn1Co4 is due to Pt occupying Zn vacancies, thus achieving effective anchoring of active metal sites.

[0082] The XPS spectra of PtCo / NC-ZnCo prepared in Examples 1-3 and Co / NC-Zn1Co4 prepared in Comparative Example 1 are as follows: Figure 14 As shown in a, the high-resolution Co 2p spectrum is as follows: Figure 14 As shown in b, the high-resolution Pt 4f spectrum is as follows: Figure 14 As shown in c, the high-resolution N1s spectrum is as follows: Figure 14 As shown in d. (Through) Figure 14 As can be seen from the peak of Pt 4f appearing near 59.00 eV, it is confirmed that Pt exists in all nanomaterials. Figure 14 b shows that the characteristic fitting peaks are located at 778.33, 779.93, and 782.11 eV, corresponding to the Co 2p of Co / NC-Zn1Co4. 3 / 2 Co in the orbit 0 Co 3+ and Co 2+ Compared to unalloyed ZnCo, PtCo / NC-Zn 0.3 Co 4.7 PtCo / NC-Zn 0.3 Co 4.7 Co 2+ Co 3+ and Co 0 The peak position remained almost unchanged. With increasing Zn source content, the Co fitting peak in PtCo / NC-Zn1Co4 shifted to higher binding energies. 2.5 Co 2.5 Co 2+ The fitted peak shifted by 0.84 eV, which is attributed to the transfer of electrons from Co to the more electronegative Pt (ENPt=2.28, ENCo=1.88), resulting in a decrease in the electron density at the Co site.

[0083] on the contrary, Figure 14 c indicates that in the PtCo / NC-ZnCo series of electrocatalysts, Pt 4f 5 / 2 and Pt 4f 7 / 2 The tracks are all made of Pt 2+and Pt 4+ The fitted peak composition shows that Co / NC-Zn1Co4 lacks Pt orbitals, while PtCo / NC-Zn... 0.3 Co 4.7 Pt 2+ and Pt 4+ The fitting peaks were located at 72.09 and 73.68 eV, respectively. With increasing Zn source content, PtCo / NC-Zn1Co4 and PtCo / NC-Zn... 2.5 Co 2.5 Pt 4f spectrum of Pt 2+ and Pt 4+ The fitted peaks all shifted to lower binding energies, indicating an increase in the electron density of Pt sites. This confirms the charge redistribution on the PtCo alloy surface, resulting in electron-rich Pt and electron-deficient Co sites, which is beneficial for H. + The adsorption of H2O optimizes the acidic hydrogen evolution kinetics. Figure 14 The value d indicates that the pyridine nitrogen content of all samples is similar (28.11~42.06%), indicating that Zn vacancies and PtCo alloying do not significantly change the support, thus ruling out the regulatory effect of nitrogen on hydrogen evolution performance.

[0084] Performance testing

[0085] The electrocatalytic acidic hydrogen evolution performance of the PtCo / NC-ZnCo prepared in Examples 1-3 and the Co / NC-Zn1Co4 prepared in Comparative Example 1 was tested. Taking Example 1 as an example, 5 mg of PtCo / NC-Zn1Co4 was dispersed in 500 μL of ethanol, and 20 μL of Nafion solution (5 wt%) was added to form a homogeneous slurry. The slurry was sonicated for 1 h, and then 100 μL of the resulting mixed solution was dropped onto the surface of pretreated carbon paper, with a loading of 1 mg / cm³. -2 The carbon paper was used as the working electrode. Pretreatment of the carbon paper involved placing it in concentrated nitric acid and boiling it at 60°C for 5-6 minutes. During performance testing, the treatment methods for Examples 2, 3, and Comparative Example 1 were the same as in Example 1.

[0086] The linear and cyclic voltammetric curves of this invention were tested using a CHI 660E electrochemical workstation in 0.5M H2SO4 solution, with Ag / AgCl as the reference electrode and a platinum sheet electrode as the counter electrode. Before each experiment, the electrolyte was pre-purged with nitrogen for 30 min to remove oxygen, and the scan rate was set to 5 mV / s. -1 .

[0087] Electrochemical impedance spectroscopy (EIS): obtained at a DC potential (-0.096 V vs. RHE), corresponding to a current density of 10 mA cm⁻¹ in the hydrogen evolution LSV curve. -2 The potential was measured at a frequency of 0.01~10.5 Hz, amplitude is 0.005V.

[0088] Tafel curve: obtained by iR-compensated linear polarization curve, the selected range is the Faraday interval where hydrogen evolution occurs.

[0089] Double-layer capacitor (C dl ): By using different scan rates (5~40mV s) within the non-Radical interval of hydrogen evolution (-0.002~0.098V vs. RHE). -1 The interval is 5mV s -1 ) Perform CV testing and calculate the results.

[0090] Among them, Pt / C refers to commercially available Pt / C with a Pt content of 20wt%.

[0091] The acidic hydrogen evolution performance of the materials prepared in each embodiment and Comparative Example 1 is as follows: Figure 15 As shown, by Figure 15 As can be seen from the iR-compensated LSV curves, the overpotential of the PtCo / NC-ZnCo series nanomaterials is significantly lower than that of Co / NC-Zn1Co4, confirming the important roles of Zn vacancies and PtCo alloying in enhancing hydrogen evolution activity. Among the synthesized nanomaterials, the PtCo / NC-Zn1Co4 nanomaterial prepared in Example 1 of this invention exhibits the highest acidic hydrogen evolution activity, requiring only 19 mV overpotential to reach 0.01 A cm⁻¹. -2 Especially at high current densities (>0.2A cm⁻¹) -2 The activity is better than that of 20wt% Pt / C.

[0092] This invention evaluates the kinetic performance of the catalyst for electrocatalytic hydrogen evolution using the Tafel slope in the Tafel curve of overpotential (η) versus log(j). The Tafel slope of the PtCo / NC-Zn1Co4 nanomaterial in Example 1 was calculated using the iR-compensated LSV curve. Figure 15 b indicates that Tafel analysis reveals the Tafel slope of PtCo / NC-Zn1Co4 to be 35.24 mV dec. -1 The Tafel slope (36.61 mV dec) is below 20 wt% Pt / C. -1 The value is much smaller than that of Co / NC-Zn1Co4 (170.52 mVdec). -1 ), surface PtCo alloying significantly optimized hydrogen evolution kinetics.

[0093] Furthermore, CV scanning tests were performed on the nanomaterials obtained in Examples 1-3 and Comparative Example 1 within the non-Radar range of -0.002 to 0.098 V vs. RHE to analyze the electrochemical surface area of ​​the electrocatalysts. The bilayer capacitance (C) obtained from the CV measurements was... dl () Figure 15 c) Shows that the C of the PtCo / NC-Zn1Co4 nanomaterials prepared in Example 1 of this invention is... dl The highest value (56.04 mFcm) -2 ), is Co / NC-Zn1Co4 (42.87mF cm -2 The PtCo alloying increases the electrochemically active surface area by 1.31 times, indicating that PtCo alloying increases the electrochemically active surface area.

[0094] The nanomaterials obtained in Examples 1-3 and Comparative Example 1 were subjected to EIS testing at -0.102V vs. RHE. Figure 15 The fitted equivalent circuit diagram embedded in d includes the solution resistance (R) s ), charge transfer resistance (R) ct ) and capacitor elements (CPE). Comparative Example 1: R of Co / NC-Zn1Co4 nanomaterials ct The Ω value (18.87 Ω) is significantly higher than that of the PtCo / NC-Zn-Co series electrocatalysts in Examples 1, and is 21.21 times that of the PtCo / NC-Zn1Co4 nanomaterial (0.89 Ω) obtained in Example 1, indicating that PtCo alloying significantly accelerates interfacial charge transfer. These results demonstrate that Zn vacancy formation and the PtCo alloy structure synergistically improve the conductivity of Co / NC, thereby enhancing the acidic hydrogen evolution performance.

[0095] like Figure 15 As shown in e, the TOF (1.714 s⁻¹) of the PtCo / NC-Zn1Co₄ nanomaterial obtained in Example 1 is... -1 The TOF of the Co / NC-Zn1Co4 nanomaterial obtained in Comparative Example 1 and the commercial 20wt% Pt / C nanomaterial exceeded that of the standard, indicating that it possesses the highest intrinsic activity and the fastest catalytic conversion per unit active site in acidic hydrogen evolution. Furthermore, as... Figure 15 As shown in f, PtCo / NC-Zn1Co4 also exhibits the largest radar map area, reflecting its overall superior hydrogen evolution performance.

[0096] The PtCo / NC-Zn1Co4 nanomaterials of Example 1 were used at 0.1 A cm⁻¹ -2 The constant current stability test curve under current density is as follows: Figure 15 As shown in g. The study found that at 0.1A cm... -2 After 100 hours of continuous electrolysis, the electrode voltage change rate of PtCo / NC-Zn1Co4 was only 0.52 mV / h.-1 This confirms its excellent electrocatalytic stability.

[0097] Finally, the PtCo / NC-Zn1Co4 obtained in Example 1 was sprayed onto carbon paper as the cathode, and commercial RuO2 was sprayed onto titanium fiber felt as the anode. The electrodes were separated by an N115 proton exchange membrane and hot-pressed to form a PtCo / NC-Zn1Co4‖RuO2 membrane electrode assembly. The LSV curve of the PtCo / NC-Zn1Co4‖RuO2 membrane electrode at 60°C with iR compensation is shown below. Figure 16 a) indicates that only 1.94V is needed to drive a 0.1A cm -2 And it is not significantly different from the curve without iR compensation. Furthermore, such as the timing potential curve ( Figure 16 As shown in b), the membrane electrode can stably electrolyze for more than 100 hours, demonstrating its potential for practical PEM water electrolysis applications.

[0098] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for preparing a PtCo alloy catalyst supported on nitrogen-carbon nanospheres, characterized in that, The steps include the following: Step 1: Disperse Co(NO3)2·6H2O and Zn(NO3)2·6H2O in methanol and stir until homogeneous to form solution A. Disperse 2-methylimidazole in methanol and stir until homogeneous to form solution B. Add solution A dropwise to solution B, stir, and react at room temperature. After washing and drying, obtain ZIF-67-ZnCo series precursors. Step 2: Disperse the prepared ZIF-67-ZnCo series precursor in ethanol and stir until homogeneous to form solution C. Disperse H2PtCl6·6H2O in deionized water and stir until homogeneous to form solution D. Add solution D dropwise to solution C. After reacting at room temperature, wash and dry to obtain Pt-ZIF-67-ZnCo. Step 3: The prepared Pt-ZIF-67-ZnCo was annealed to obtain a nitrogen-carbon nanosphere-supported PtCo alloy catalyst.

2. The method for preparing the PtCo alloy catalyst supported on nitrogen-carbon nanospheres according to claim 1, characterized in that, In step one, the molar ratio of the inorganic metal source formed by Co(NO3)2·6H2O and Zn(NO3)2·6H2O to 2-methylimidazole is 1:(6~10).

3. The method for preparing the PtCo alloy catalyst supported on nitrogen-carbon nanospheres according to claim 1, characterized in that, In step one, the molar ratio of Co(NO3)2·6H2O to Zn(NO3)2·6H2O is (1~16):

1.

4. The method for preparing the PtCo alloy catalyst supported on nitrogen-carbon nanospheres according to claim 1, characterized in that, In step one, the reaction is carried out at room temperature for 22-26 hours.

5. The method for preparing the PtCo alloy catalyst supported on nitrogen-carbon nanospheres according to claim 1, characterized in that, In step two, the molar ratio of added H2PtCl6·6H2O to Co(NO3)2·6H2O is 1:(125~235).

6. The method for preparing the PtCo alloy catalyst supported on nitrogen-carbon nanospheres according to claim 1, characterized in that, In step three, the annealing conditions are as follows: high-purity argon is used as the annealing atmosphere, the annealing temperature is 950~980℃, and the annealing time is 2~3h.

7. The method for preparing the PtCo alloy catalyst supported on nitrogen-carbon nanospheres according to claim 3, characterized in that, In step one, the molar ratio of Co(NO3)2·6H2O to Zn(NO3)2·6H2O is 4:

1.

8. A nitrogen-carbon nanosphere-supported PtCo alloy catalyst, characterized in that, The PtCo alloy catalyst supported on nitrogen-carbon nanospheres was prepared using the method described in any one of claims 1 to 7.

9. The nitrogen-carbon nanosphere-supported PtCo alloy catalyst according to claim 8, characterized in that, The nitrogen-carbon nanosphere-supported PtCo alloy catalyst exhibits the morphology of nitrogen-doped carbon nanotubes supporting metal nanoparticles.

10. The application of a nitrogen-carbon nanosphere-supported PtCo alloy catalyst as described in claim 8 or 9 in electrocatalytic acidic hydrogen evolution.

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