A method for preparing a high-dispersed partially disordered platinum-zinc intermetallic compound material by a confined pyrolysis strategy

Abstract

The present invention aims to provide a method for preparing highly dispersed, partially disordered platinum-zinc intermetallic compound materials using a confined pyrolysis strategy, belonging to the field of water electrolysis catalyst technology. This invention generates nitrogen-containing porous cavities and a small amount of zinc through the pyrolysis of zinc-containing metal-organic framework materials. Then, platinum atoms are confined within narrow pores inherited from the precursor through nitrogen coordination. Since zinc and platinum coexist within a confined space, confined rearranged platinum-zinc intermetallic compound materials are obtained through simple pyrolysis. This strategy not only avoids complex interface tuning between organic and inorganic precursors but also provides a general approach for constructing confined metal alloys.

Description

Technical Field

[0001] This invention belongs to the field of water electrolysis catalyst technology, specifically relating to a method for preparing highly dispersed, partially disordered platinum-zinc intermetallic compound materials using a confined pyrolysis strategy. Background Technology

[0002] Platinum-based alloys are promising catalysts for the hydrogen evolution reaction (HER). The introduction of a second transition metal endows platinum-based alloys with ligand, strain, geometric, and two-site effects, altering the electronic structure of platinum to improve its activity and stability in the HER. However, the second transition metal atoms on the surface of platinum-based alloys may rapidly dissolve into the electrolyte during acid cycling, leaving a poorly coordinated platinum surface and reducing stability.

[0003] Compared to disordered alloys, atomically ordered intermetallic compounds exhibit higher structural stability and reactivity due to the synergistic effects of geometry and electronics. Zinc's low melting point (419.5 °C) and low boiling point (907 °C) facilitate the formation of ordered platinum-zinc intermetallic compounds through annealing. However, zinc's high hydrogen overpotential leads to a large Gibbs free energy for the adsorption of the platinum-zinc intermediate (H*), consistently resulting in unsatisfactory hydrogen evolution reaction reactivity.

[0004] Previous research has mainly focused on improving material properties through nonmetallic element doping, lattice strain engineering, and intermetallic trimetallic design. However, these strategies cannot fundamentally overcome the hydrogen repulsion property of zinc, and current research still lacks methods to manipulate the atomic arrangement of platinum and zinc atoms to enhance the catalytic activity of platinum intermetallic compounds. Summary of the Invention

[0005] This invention addresses the problem of unfavorable proton adsorption on the atomic layer surface of zinc by providing a method for preparing highly dispersed, partially disordered platinum-zinc intermetallic compound materials using a confined pyrolysis strategy. This method synthesizes platinum-zinc intermetallic compounds with rearranged atoms through confined pyrolysis, and the rearranged structure stimulates the intrinsic activity of the platinum-zinc intermetallic compounds, thereby improving the material's performance.

[0006] The present invention adopts the following technical solution:

[0007] A method for preparing highly dispersed, partially disordered platinum-zinc intermetallic compound materials using a confined pyrolysis strategy is disclosed. The method uses zinc-containing metal-organic framework-derived carbon as a confined substrate, and further controls the pyrolysis temperature and platinum and zinc content to achieve precise preparation of rearranged platinum-zinc intermetallic compounds by spatially and coordinately confining platinum atoms.

[0008] The specific method is as follows:

[0009] S1. Disperse dimethylimidazole in methanol to obtain solution A;

[0010] S2. Disperse zinc nitrate hexahydrate in methanol to obtain solution B;

[0011] S3. Mix solution A with solution B, heat in a water bath at 35°C for 4 hours, wash five times with methanol and ethanol after heating, and dry overnight to obtain ZIF-8;

[0012] S4. Carbonize ZIF-8 at 1000℃ for 3 hours in an H2 / Ar atmosphere to obtain derived carbon;

[0013] S5. Add chloroplatinic acid to deionized water containing derivatized carbon, heat in a water bath at 60°C for 16 hours, wash three times with deionized water after heating, and dry overnight to obtain the precursor.

[0014] S6. The precursor was heated at 800 °C for 2 h in an H2 / Ar atmosphere to obtain a black solid powder, namely the platinum-zinc intermetallic compound.

[0015] Furthermore, in S1, the ratio of dimethylimidazole to methanol is 50-150 mmol: 30-90 mL.

[0016] Furthermore, in S2, the ratio of zinc nitrate hexahydrate to methanol is 20-40 mmol: 180-540 mL.

[0017] Furthermore, in S5, the ratio of chloroplatinic acid, derived carbon, and deionized water is 100-300 µL: 25-100 mg: 7-28 mL.

[0018] Furthermore, the derived carbon after ZIF-8 carbonization contains residual zinc.

[0019] Furthermore, in S6, the platinum-zinc intermetallic compound contains a partially substituted disordered structure.

[0020] The beneficial effects of this invention are as follows:

[0021] This invention proposes a restricted high-temperature pyrolysis strategy, different from traditional in-situ or low-temperature pyrolysis, to achieve localized disorder in ordered platinum-zinc intermetallic compounds. First, a zinc-containing metal-organic framework material is pyrolyzed to generate nitrogen-containing porous cavities and a small amount of zinc. Then, platinum atoms are confined within narrow pores inherited from the precursor through nitrogen coordination. Finally, a confined rearranged platinum-zinc intermetallic compound material can be obtained through simple pyrolysis. This invention fundamentally improves the catalytic activity and stability of the hydrogen evolution reaction by constructing locally disordered platinum atoms within a structurally ordered platinum-zinc intermetallic compound. Attached Figure Description

[0022] Figure 1 SEM image of the metal-organic framework-derived carbon prepared in Example 1;

[0023] Figure 2 STEM image of carbon-confined platinum derived from a metal-organic framework prepared in Example 1;

[0024] Figure 3 TEM image of the platinum-zinc intermetallic compound with partial rearrangement prepared in Example 1;

[0025] Figure 4 STEM image of the partially rearranged platinum-zinc intermetallic compound prepared in Example 1, and intensity map corresponding to the linear contour of the rearranged portion;

[0026] Figure 5 XRD images of various precursors and catalyst materials prepared in Example 1;

[0027] Figure 6 A comparison of the catalytic performance of the catalyst material prepared in Example 1 and most platinum-based noble metal catalysts in the hydrogen evolution reaction of water electrolysis;

[0028] Figure 7 The performance of the catalyst material prepared in Example 1 on the PEM device at different temperatures.

[0029] Figure 8 TEM image of the partially disordered platinum-zinc intermetallic compound prepared in Example 2;

[0030] Figure 9 TEM image of the platinum-zinc intermetallic compound prepared in Example 3 after stability testing. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below, but the scope of protection of the present invention is not limited to the following embodiments.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains, and all materials publicly cited herein and cited by them are incorporated herein by reference.

[0033] Equivalent technologies of the specific embodiments described herein that are readily apparent to those skilled in the art through routine experimentation are included in this application.

[0034] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the instruments and equipment used in the following examples are all standard laboratory instruments and equipment; unless otherwise specified, the experimental materials used in the following examples were all purchased from regular biochemical reagent stores.

[0035] Example 1

[0036] A method for preparing highly dispersed, partially disordered platinum-zinc intermetallic compound materials using a confined pyrolysis strategy is described below:

[0037] (1) 11.82 mg of dimethylimidazole was dispersed in 60 ml of methanol to obtain solution A; 10.71 mg of zinc nitrate hexahydrate was dispersed in 360 mL of methanol to obtain solution B; solution A and solution B were mixed, heated in a water bath at 35 °C for 4 h, washed five times with methanol and ethanol, and dried overnight to obtain ZIF-8;

[0038] (2) The ZIF-8 obtained in the above steps was carbonized at 1000 °C for 3 hours in an H2 / Ar atmosphere to obtain the derived carbon;

[0039] (3) Add 250µL of chloroplatinic acid to 14 mL of deionized water containing 50 mg of the derived carbon obtained in the above steps, heat in a water bath at 60°C for 16 hours, wash three times with deionized water, and dry overnight to obtain the precursor.

[0040] (4) The precursor obtained above was heated at 800 °C for 2 hours in an H2 / Ar atmosphere to obtain a black solid powder.

[0041] Figure 1 The image shows a SEM image of the metal-organic framework-derived carbon prepared in Example 1. As can be seen from the image, the polyhedral shape is well preserved.

[0042] Figure 2 STEM image of carbon-confined platinum derived from a metal-organic framework prepared in Example 1. As can be seen from the image, platinum and zinc exist in atomic form.

[0043] Figure 3 TEM images of a partially disordered platinum-zinc intermetallic compound prepared for Example 1 are shown. The images reveal particles with sizes ranging from 10 to 20 nm within the material.

[0044] Figure 4 This is a STEM image of the partially rearranged platinum-zinc intermetallic compound prepared in Example 1. The image shows that the atomic arrangement within the ordered intermetallic compound exhibits a disordered state where platinum partially substitutes for zinc.

[0045] Figure 5 The images show XRD patterns of various precursors and catalysts prepared in Example 1. As can be seen from the figures, this invention successfully prepared platinum-zinc intermetallic compound materials.

[0046] Figure 6This figure compares the catalytic performance of the catalyst material prepared in Example 1 with that of most platinum-based noble metal catalysts in the hydrogen evolution reaction of water electrolysis. As can be seen from the figure, the present invention exhibits superior catalytic performance in water electrolysis compared to most platinum-based noble metal catalysts.

[0047] Figure 7 The performance of the catalyst material prepared in Example 1 on a PEM device at different temperatures is shown. PEM water electrolysis for hydrogen production refers to the process of producing hydrogen using a proton exchange membrane as a solid electrolyte and pure water or a low-concentration acidic solution as the raw material. In short, it uses electrical energy to decompose water molecules into hydrogen and oxygen. This process is completed with the assistance of a proton exchange membrane; hydrogen is generated on one side of the membrane, and oxygen is generated on the other, achieving precise control of water electrolysis. This material is used for the hydrogen evolution reaction in acidic electrochemical water decomposition. The lower the voltage required to reach a certain current density, the better the hydrogen evolution performance of the material. As shown in the figure, at 70 °C, the material only requires 1.5 V to reach 1 A cm⁻¹. -2 This indicates that the material has certain application potential at a near-industrial scale.

[0048] Example 2

[0049] A method for preparing highly dispersed, partially disordered platinum-zinc intermetallic compound materials using a confined pyrolysis strategy is described below:

[0050] (1) Disperse 5.91 mg of dimethylimidazole in 30 ml of methanol to obtain solution A; disperse 5.355 mg of zinc nitrate hexahydrate in 180 mL of methanol to obtain solution B; mix solution A and solution B, heat in a water bath at 35 °C for 4 h, wash five times with methanol and ethanol, and dry overnight to obtain ZIF-8; (2) Carbonize the ZIF-8 obtained in the above steps at 1000 °C for 3 hours in an H2 / Ar atmosphere to obtain derived carbon; (3) Add 125 µL of chloroplatinic acid to 7 mL of deionized water containing 25 mg of the derived carbon obtained in the above steps, heat in a water bath at 60 °C for 16 hours, wash three times with deionized water, and dry overnight to obtain the precursor; (4) Heat the precursor obtained above at 800 °C for 2 hours in an H2 / Ar atmosphere to obtain a black solid powder.

[0051] Figure 8 TEM images of a partially disordered platinum-zinc intermetallic compound prepared for Example 2 are shown. The images reveal the presence of particles in the material, and the dodecahedral morphology was not destroyed by subsequent high-temperature pyrolysis.

[0052] Example 3

[0053] A method for preparing highly dispersed, partially disordered platinum-zinc intermetallic compound materials using a confined pyrolysis strategy is described below:

[0054] (1) Disperse 17.73 mg of dimethylimidazole in 90 ml of methanol to obtain solution A; disperse 16.065 mg of zinc nitrate hexahydrate in 540 mL of methanol to obtain solution B; mix solution A and solution B, heat in a water bath at 35 °C for 4 h, wash five times with methanol and ethanol, and dry overnight to obtain ZIF-8; (2) Carbonize the ZIF-8 obtained in the above steps at 1000 °C for 3 hours in an H2 / Ar atmosphere to obtain derived carbon; (3) Add 300 µL of chloroplatinic acid to 28 mL of deionized water containing 100 mg of the derived carbon obtained in the above steps, heat in a water bath at 60 °C for 16 hours, wash three times with deionized water, and dry overnight to obtain the precursor; (4) Heat the precursor obtained above at 800 °C for 2 hours in an H2 / Ar atmosphere to obtain a black solid powder.

[0055] Figure 9 The image shows a TEM image of the partially disordered platinum-zinc intermetallic compound prepared in Example 3 after a stability test. As can be seen from the image, the particles in the material are largely unaggregated, and the dodecahedral morphology remains well preserved.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing highly dispersed, partially disordered platinum-zinc intermetallic compound materials using a confined pyrolysis strategy, characterized in that: Using zinc-containing metal-organic framework-derived carbon as a confined substrate, and through spatial-coordination confinement of platinum atoms, the pyrolysis temperature and platinum and zinc contents are further controlled to achieve the precise preparation of rearranged platinum-zinc intermetallic compounds. The specific method is as follows: S1. Disperse dimethylimidazole in methanol to obtain solution A; S2. Disperse zinc nitrate hexahydrate in methanol to obtain solution B; S3. Mix solution A with solution B, heat in a water bath at 35°C for 4 hours, wash five times with methanol and ethanol after heating, and dry overnight to obtain ZIF-8; S4. ZIF-8 is carbonized at 1000°C for 3 hours in an H2 / Ar atmosphere to obtain derived carbon; the derived carbon after ZIF-8 carbonization contains zinc element; S5. Add chloroplatinic acid to deionized water containing derivatized carbon, heat in a water bath at 60°C for 16 hours, wash three times with deionized water after heating, and dry overnight to obtain the precursor. S6. The precursor is heated at 800 °C for 2 h in an H2 / Ar atmosphere to obtain a black solid powder, namely a platinum-zinc intermetallic compound; the platinum-zinc intermetallic compound contains a partially substituted disordered structure.

2. The method for preparing highly dispersed, partially disordered platinum-zinc intermetallic compound materials using a confined pyrolysis strategy according to claim 1, characterized in that: In S1, the ratio of dimethylimidazole to methanol is 50-150 mmol: 30-90 mL.

3. The method for preparing highly dispersed, partially disordered platinum-zinc intermetallic compound materials using a confined pyrolysis strategy according to claim 1, characterized in that: In S2, the ratio of zinc nitrate hexahydrate to methanol is 20-40 mmol: 180-540 mL.

4. The method for preparing highly dispersed, partially disordered platinum-zinc intermetallic compound materials using a confined pyrolysis strategy according to claim 1, characterized in that: In S5, the ratio of chloroplatinic acid, derived carbon, and deionized water is 100-300 µL: 25-100 mg: 7-28 mL.

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