Preparation method and application of double-shell hollow porous carbon-supported Ni single-atom catalyst

Abstract

The invention discloses a preparation method and use of a double-shell hollow porous carbon-supported Ni single-atom catalyst, the method comprising the following steps: dissolving zinc acetate dihydrate, nickel acetate tetrahydrate and terephthalic acid in N, N-2 methylformamide to form a mixed solution, reacting at room temperature, and obtaining ZnNi-MOF-5 solid nanoparticles after multiple centrifugation and washing; ZnNi-MOF-5 solid nanoparticles are dispersed in ethanol to form a suspension C, 2-methylimidazole is dissolved in ethanol, a small amount of triethylamine is added thereto to form a solution D, and the solution D is added to the suspension C, reacted under low temperature conditions, and subsequently centrifuged to obtain ZnNi-ZIF double-shell hollow nanoparticles, which are then placed in an argon atmosphere for annealing to obtain a double-shell hollow porous carbon-supported Ni single-atom catalyst. The prepared double-shell hollow porous carbon-supported Ni single atom can be applied to a catalyst for high-performance electrocatalytic CO2 reduction.

Description

Technical Field

[0001] The present invention relates to the technical field of synthesis of single-atom catalysts, and in particular to a preparation method and application of a double-shell hollow porous carbon-supported Ni single-atom catalyst. Background Art

[0002] Due to the rapid development of industry, humanity's consumption of fossil fuels is becoming increasingly widespread, and increasing carbon dioxide emissions are leading to the greenhouse effect, posing a threat to the natural environment and human civilization in many regions of the world. Because catalytic reactions occur on the surface, the bulk atoms of metal-based catalysts are far less important than the surface atoms. Consequently, the large size of metal catalysts limits the effective utilization of the metal component. When a reaction requires expensive precious metals as active ingredients, developing highly dispersed metal catalysts with a high proportion of surface metal atoms is crucial to improve metal utilization efficiency and reduce catalyst costs. Single-atom catalysts differ from nanocatalysts and sub-nanocatalysts because when particle dispersion reaches single-atom size, their energy level structure and electronic structure undergo fundamental changes, such as a dramatic increase in surface free energy, quantum size effects, an unsaturated coordination environment, and interactions with the metal support. It is precisely because of these unique structural characteristics that single-atom catalysts exhibit exceptional activity, selectivity, and stability. However, when single-atom catalysts are prepared and reacting, due to the sharp increase in surface free energy and the lack of elements such as N to coordinate with the single-atom catalysts to anchor the single-atom catalysts on the carbon support, the single-atom catalysts will couple to form clusters. With the formation of clusters, the active sites of the single-atom catalysts will decrease sharply, resulting in catalyst deactivation. Summary of the Invention

[0003] The purpose of the present invention is to provide a preparation method and use of a double-shell hollow porous carbon-supported Ni single-atom catalyst, which can improve the selectivity and catalytic activity for electrocatalytic CO2 reduction.

[0004] In one aspect of the present invention, a method for preparing a double-shell hollow porous carbon-supported Ni single-atom catalyst is provided. According to an embodiment of the present invention, the method comprises the following steps:

[0005] (1) dissolving terephthalic acid in N,N-dimethylformamide to form solution A;

[0006] (2) dissolving nickel acetate tetrahydrate and zinc acetate dihydrate in N,N-dimethylformamide to form solution B;

[0007] (3) Solution A was slowly added dropwise to solution B, and after being thoroughly stirred, the mixture was placed in a reactor and placed in an oven for reaction. Finally, the product was centrifuged and washed with N,N-dimethylformamide to obtain ZnNi-MOF-5 solid nanoparticles;

[0008] (4) dispersing ZnNi-MOF-5 solid nanoparticles in ethanol to form suspension C;

[0009] (5) 2-Methylimidazole was dissolved in ethanol and a small amount of triethylamine was added to form solution D;

[0010] (6) slowly adding solution D dropwise to suspension C, reacting at -10 to 10°C, centrifuging the obtained product, washing it with ethanol, and drying it in an oven to obtain ZnNi-ZIF double-shell hollow nanoparticles;

[0011] (7) The ZnNi-ZIF micro-nanoparticles were placed in an argon atmosphere and annealed to obtain a double-shell hollow porous carbon-loaded Ni single-atom catalyst.

[0012] In addition, the preparation method of a double-shell hollow porous carbon-supported Ni single-atom catalyst according to the above embodiment of the present invention may also have the following additional technical features:

[0013] In some embodiments of the present invention, in step (1), the concentration of terephthalic acid is 10-30 g / L.

[0014] In some embodiments of the present invention, in step (2), the concentration of zinc acetate dihydrate is 0.126-0.1386 mol / L, the concentration of nickel acetate tetrahydrate is 0.014-0.0126 mol / L, and the total concentration of zinc acetate dihydrate and nickel acetate tetrahydrate is 0.14 mol / L.

[0015] In some embodiments of the present invention, in step (3), the stirring temperature is room temperature, the stirring time is 15 to 30 minutes, the oven drying temperature is 90 to 100° C., the drying time is 6 to 10 hours, and washing is performed 2 to 4 times with N,N-2-methylformamide.

[0016] In some embodiments of the present invention, in step (5), the concentration of 2-methylimidazole is 20-40 g / L, and the volume ratio of triethylamine to solvent ethanol is 1:600-1:300.

[0017] In some embodiments of the present invention, in step (6), the reaction time is 30 to 60 minutes, the drying temperature is 70 to 90° C., and the drying time is 10 to 16 hours.

[0018] In some embodiments of the present invention, in step (7), the annealing temperature is 700-900° C., the holding time is 2-4 h, and the heating rate is 2-10° C. / min.

[0019] In another aspect of the present invention, the present invention provides a double-shell hollow porous carbon-supported Ni single-atom catalyst prepared by the preparation method of the double-shell hollow porous carbon-supported Ni single-atom catalyst.

[0020] In another aspect of the present invention, a method for preparing a flow battery cathode is provided, comprising the following steps:

[0021] The double-shell hollow porous carbon supported Ni single atom catalyst was dispersed in a mixed solution of ethanol and water, ultrasonicated for 3-8 minutes to prepare a suspension, added with Nafion adhesive, and then sprayed on carbon paper with a loading of 0.5-1.0 mg cm -2 , and then placed in a vacuum drying oven at 70°C for 2 hours. The carbon paper loaded with the catalyst after drying is the cathode of the flow battery;

[0022] Among them, the volume ratio of ethanol to water is 4:1 to 9:1, the volume ratio of Nafion binder to suspension is 1:2000 to 1:1000, and the thickness of carbon paper is 0.21 + 0.01mm, the carbon paper is hydrophobic carbon paper, the size is 2cm*2cm, and the model is SGL29BC or SGL28BC.

[0023] In another aspect of the present invention, the present invention proposes a flow battery, which uses a 0.1-1 mol / L KOH solution or a 0.1-1.0 mol / L KHCO3 solution as the electrolyte, the flow battery cathode as the cathode material, and the flow battery anode material is a platinum sheet electrode with a size of 15mm*15mm*0.2mm.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1) Due to its rich nitrogen content, the double-shell hollow porous carbon-supported Ni single-atom catalyst can anchor the active metal sites on the carbon matrix, which not only increases the loading amount of the single-atom catalyst but also improves the stability of the single atom; secondly, the double-shell hollow porous carbon-supported Ni single-atom catalyst can change the adsorption and desorption selectivity of the active components on the catalyst for different molecules, thereby improving the selectivity of the catalyst.

[0026] 2) The double-shell hollow porous carbon-supported Ni single-atom catalyst of the present invention has a double-shell hollow structure, and the Ni single-atom catalyst is uniformly dispersed in the form of single atoms on the inner and outer layers of the double-shell porous carbon support. The double-shell structure of the carbon support can accelerate the mass transfer process during the electrocatalytic process, thereby improving the kinetic process of the catalytic reaction.

[0027] 3) The double-shell hollow porous carbon-supported Ni single-atom catalyst prepared by the present invention, ZIF (zeolite imidazolate framework material) as a subclass of MOFs, can achieve good dispersion and stability of the single-atom catalyst because its derived carbon material not only has a rich pore structure and a large specific surface area, but also is rich in nitrogen elements that can anchor metal atoms.

[0028] 4) The synthesis method used in the present invention, namely solvent-assisted ligand exchange combined with heat treatment process, can directly achieve good dispersion of single atoms, thereby showing excellent catalytic selectivity, reducing the separation cost of subsequent products, and at the same time having a higher current for CO2 reduction at low potential.

[0029] 5) The preparation method of the present invention is simple and easy to operate, safe and pollution-free, and has low cost compared to noble metal-based catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a FESEM image of Zn93Ni7-MOF-5 solid nanoparticles prepared in Example 1;

[0031] Figure 2 This is the FESEM image of the Zn93Ni7-ZIF double-shell hollow nanoparticles prepared in Example 1;

[0032] Figure 3 TEM image of Zn93Ni7-ZIF double-shell hollow nanoparticles prepared in Example 1;

[0033] Figure 4 TEM image of the double-shell hollow porous carbon-supported Ni single-atom catalyst prepared in Example 1;

[0034] Figure 5 XRD diffraction patterns of ZIF-8, Zn93Ni7-ZIF double-shell hollow nanoparticles prepared in Example 1, and Zn91Ni9-ZIF double-shell hollow nanoparticles prepared in the comparative example;

[0035] Figure 6 XRD diffraction patterns of double-shell hollow porous carbon-supported Ni single-atom catalysts prepared in Example 1 and the comparative example;

[0036] Figure 7 Faraday efficiency diagram of CO2 reduction catalyzed by double-shell hollow porous carbon-supported Ni single-atom catalysts prepared in Example 1 and Comparative Example;

[0037] Figure 8 Current performance diagram of CO2 reduction catalyzed by double-shell hollow porous carbon-supported Ni single-atom catalyst prepared in Example 1 and Comparative Example. DETAILED DESCRIPTION

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0039] Example 1

[0040] A method for preparing a double-shell hollow porous carbon-supported Ni single-atom catalyst specifically comprises the following steps:

[0041] (1) Dissolve 1.429 g zinc acetate dihydrate and 121.93 mg nickel acetate tetrahydrate in 35 mL N,N-dimethylformamide and dissolve them by ultrasonication to obtain solution B. Add 15 mL N,N-dimethylformamide to 150 mg terephthalic acid and ultrasonicate for 15 min to obtain solution A. Slowly add solution A to solution B, stir at room temperature for 15 min, place in a reactor, and place in a 95°C oven for reaction for 10 h.

[0042] (2) washing with N,N-dimethylformamide by centrifugation several times to obtain Zn93Ni7-MOF-5 solid nanoparticle powder;

[0043] (3) Zn93Ni7-MOF-5 solid nanoparticles were dispersed in 10 mL of ethanol to obtain dispersion C. 1 g of 2-methylimidazole was dissolved in 30 mL of ethanol and 80 μL of triethylamine was added to obtain solution D. Solution D was slowly added dropwise to dispersion C and stirred at 0°C for 30 min.

[0044] (4) After washing with ethanol by centrifugation for several times, the mixture was placed in an oven at 80°C for 12 h to obtain Zn93Ni7-ZIF double-shell hollow nanoparticle powder;

[0045] (5) The Zn93Ni7-ZIF double-shell hollow nanoparticles were placed in argon and carbonized at 800°C for 2 h at a heating rate of 2°C / min to obtain a double-shell hollow porous carbon-supported Ni single-atom catalyst.

[0046] Figure 1 This is a FESEM photograph of Zn93Ni7-MOF-5 solid nanoparticles prepared in this example. The particle size is 200nm~1.5μm.

[0047] Figure 2 This is a FESEM photograph of the Zn93Ni-ZIF double-shell hollow nanoparticles prepared in this example. The figure shows the double-shell hollow structure of the Zn93Ni7-ZIF nanoparticles.

[0048] Figure 3 This is a TEM image of the Zn93Ni7-ZIF double-shell hollow nanoparticles prepared in this example, from which the double-shell hollow structure of the Zn93Ni7-ZIF nanoparticles can be clearly seen.

[0049] Figure 4 This is a TEM image of the Zn93Ni7-ZIF double-shell hollow nanoparticle-derived double-shell hollow porous carbon-supported Ni single-atom catalyst prepared in this example. It can be seen that it has an obvious hollow double-shell structure.

[0050] Example 2

[0051] A method for preparing a double-shell hollow porous carbon-supported Ni single-atom catalyst specifically comprises the following steps:

[0052] (1) Dissolve 1.459 g zinc acetate dihydrate and 87.095 mg nickel acetate tetrahydrate in 35 mL N,N-dimethylformamide and dissolve them by ultrasonication to obtain solution B. Add 15 mL N,N-dimethylformamide to 150 mg terephthalic acid and ultrasonicate for 15 min to obtain solution A. Slowly add solution A to solution B, stir at room temperature for 15 min, place in a reactor, and place in a 95°C oven for reaction for 10 h.

[0053] (2) washing several times by centrifugation with N,N-dimethylformamide to obtain Zn95Ni5-MOF-5 solid nanoparticle powder;

[0054] (3) Disperse Zn95Ni5-MOF-5 solid nanoparticles in 10 mL of ethanol to obtain dispersion C. Dissolve 1 g of 2-methylimidazole in 30 mL of ethanol and add 80 μL of triethylamine to obtain solution D. Slowly add solution D dropwise to dispersion C and stir at 0°C for 30 min.

[0055] (4) After washing with ethanol by centrifugation several times, the mixture was placed in an oven at 80°C for 12 h to obtain Zn95Ni5-ZIF double-shell hollow nanoparticle powder;

[0056] (5) The Zn95Ni5-ZIF double-shell hollow nanoparticles were placed in argon and carbonized at 800°C for 2 h at a heating rate of 2°C / min to obtain a double-shell hollow porous carbon-supported Ni single-atom catalyst.

[0057] Comparative Example

[0058] A method for preparing a double-shell hollow porous carbon-supported Ni catalyst specifically comprises the following steps:

[0059] (1) Add 1.398 g zinc acetate dihydrate and 156.92 mg nickel acetate tetrahydrate to 35 mL N,N-dimethylformamide and ultrasonicate for 15 min to obtain solution B. Add 15 mL N,N-dimethylformamide to 150 mg terephthalic acid and ultrasonicate for 15 min to obtain solution A. Slowly add solution A to solution B, stir at room temperature for 15 min, and place in a 95°C oven to react for 10 h.

[0060] (2) washing several times by centrifugation with N,N-dimethylformamide to obtain Zn91Ni9-MOF-5 solid nanoparticle powder;

[0061] (3) Zn91Ni9-MOF-5 solid nanoparticles were dispersed in 10 mL of ethanol to obtain dispersion C. 2-Methylimidazole was dissolved in 30 mL of ethanol and 80 μL of triethylamine was added to obtain solution D. Solution D was slowly added dropwise to dispersion C and stirred at 0°C for 30 min.

[0062] (4) After washing with ethanol by centrifugation for several times, the mixture was placed in an oven at 80°C and dried for 12 h to obtain Zn91Ni9-ZIF double-shell hollow nanoparticle powder;

[0063] (5) The Zn91Ni9-ZIF double-shell hollow nanoparticles prepared in Example 2 were placed in argon and carbonized at 800°C for 2 h at a heating rate of 2°C / min to obtain a double-shell hollow porous carbon-supported Ni catalyst.

[0064] Figure 5 This is the XRD diffraction pattern of Zn91Ni9-ZIF and Zn93Ni7-ZIF double-shell hollow nanoparticles prepared based on Example 1 and the comparative example. It can be seen from the figure that the peak positions of the XRD diffraction patterns of Zn91Ni9-ZIF and Zn93Ni7-ZIF double-shell hollow nanoparticles are the same as those of the XRD diffraction pattern of ZIF-8. The doping of Ni does not change the physical phase, indicating that no new substance is generated.

[0065] Figure 6The XRD diffraction patterns of the double-shell hollow porous carbon-supported Ni single-atom catalyst samples prepared in Example 1 and the comparative example; It can be seen from the XRD diffraction patterns that the Zn93Ni7-ZIF-derived double-shell hollow porous carbon-supported Ni single-atom catalyst sample has only one carbon peak in its XRD, and no metallic nickel peak appears, indicating that nickel exists in the form of a single atom. The Zn91Ni9-ZIF-derived double-shell hollow porous carbon-supported Ni single-atom catalyst sample has not only a carbon peak but also a metallic nickel peak in its XRD, indicating that when the Ni doping amount exceeds a certain value (about 10%), nickel will agglomerate after high-temperature annealing. This is because the single-atom Ni has a large specific surface area and high free energy, and the single atoms will agglomerate autonomously during high-temperature annealing, and Ni is no longer anchored on the carbon support in the form of a single atom. Combined Figure 7 It can be seen that when the catalyst Ni agglomerates, its CO Faraday efficiency decreases compared with that of the non-agglomerated one. Specifically, the CO Faraday efficiency of the Zn93Ni7-ZIF-derived double-shell porous carbon-supported Ni single-atom catalyst sample is significantly improved compared with the CO Faraday efficiency of the Zn91Ni9-ZIF-derived double-shell porous carbon-supported Ni catalyst sample.

[0066] Example 3

[0067] A method for preparing a flow battery cathode comprises the following steps: taking out 15 mg of each of the double-shell hollow porous carbon-supported Ni single-atom catalysts prepared in Example 1 and the comparative example, dispersing the catalysts in a 60 mL mixed solution of ethanol and water (the volume ratio of ethanol to water being 4:1), ultrasonicating for 5 minutes to completely disperse the double-shell hollow porous carbon-supported Ni single-atom catalyst in the mixed solution to prepare a suspension, adding 20 μL of Nafion adhesive, and spraying the catalyst onto a 2 cm*2 cm carbon paper with a loading of 1.0 mg cm -2 , and then placed in a vacuum drying oven at 70°C for 2 hours. The carbon paper loaded with the catalyst after drying is the cathode of the flow battery.

[0068] A flow battery uses dried catalyst-loaded carbon paper as the cathode of the flow battery, a 1 mol / L KOH solution as the electrolyte, and a platinum sheet as the anode.

[0069] The flow cell was tested for electrocatalytic performance in the voltage range of -0.2 to -0.8 V.

[0070] Figure 7The Faraday efficiency of the double-shell hollow porous carbon supported Ni single-atom catalyst sample prepared in this embodiment; for single-atom catalysts, due to the lack of continuous active sites, it is difficult to directly convert the intermediate products in the CO2 conversion process into high-order products, such as products containing two carbons (ethanol, ethylene, etc.), and there are almost no liquid products such as formic acid. It is mainly gaseous products CO and H2, which are produced by Figure 7 It can be seen that the Zn93Ni7-ZIF derived double-shell hollow porous carbon supported Ni single atom catalyst has a very high CO Faraday efficiency (up to nearly 90%), indicating that the catalyst has a high selectivity for catalyzing the conversion of CO2 to CO, while the Faraday efficiency of H2 is basically stable at below 5%, indicating that the catalyst has a good inhibitory effect on the hydrogen evolution side reaction. Figure 8 This is a graph showing the current performance of the double-shell hollow porous carbon-supported Ni single-atom catalyst sample prepared in this example. It can be seen that the double-shell hollow porous carbon-supported Ni single-atom catalyst exhibits a high current at low potentials. Therefore, the prepared double-shell hollow porous carbon-supported Ni single-atom catalyst can be applied to high-performance electrocatalytic CO2 reduction to CO.

[0071] The above content is merely an example and explanation of the structure of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a double-shell hollow porous carbon-supported Ni single-atom catalyst, characterized in that: The following steps are involved: (1) Dissolve terephthalic acid in N,N-dimethylformamide to form solution A; (2) dissolving nickel acetate tetrahydrate and zinc acetate dihydrate in N,N-dimethylformamide to form solution B; (3) Solution A was slowly added dropwise to solution B, and after being thoroughly stirred, the mixture was placed in a reactor and placed in an oven for reaction. Finally, the product was centrifuged and washed with N,N-dimethylformamide to obtain ZnNi-MOF-5 solid nanoparticles; (4) dispersing ZnNi-MOF-5 solid nanoparticles in ethanol to form suspension C; (5) Dissolve 2-methylimidazole in ethanol and add a small amount of triethylamine to form solution D; (6) Solution D was slowly added dropwise to suspension C, and the reaction was carried out at -10~10°C. The obtained product was centrifuged, washed with ethanol, and dried in an oven to obtain ZnNi-ZIF double-shell hollow nanoparticles; (7) The ZnNi-ZIF double-shell hollow nanoparticles were placed in an argon atmosphere and annealed to obtain double-shell hollow porous carbon-supported Ni single-atom catalysts, wherein the annealing temperature was 700~900℃, the holding time was 2~4 h, and the heating rate was 2~10℃ / min.

2. The method for preparing a double-shell hollow porous carbon-supported Ni single-atom catalyst according to claim 1, characterized in that: In the step (1), the concentration of terephthalic acid is 10-30 g / L.

3. The method for preparing a double-shell hollow porous carbon-supported Ni single-atom catalyst according to claim 1, characterized in that: In the step (2), the concentration of zinc acetate dihydrate is 0.126-0.1386 mol / L, the concentration of nickel acetate tetrahydrate is 0.014-0.0126 mol / L, and the total concentration of zinc acetate dihydrate and nickel acetate tetrahydrate is 0.14 mol / L.

4. The method for preparing a double-shell hollow porous carbon-supported Ni single-atom catalyst according to claim 1, characterized in that: In the step (3), the stirring temperature is room temperature, the stirring time is 15-30 min, the oven drying temperature is 90-100° C., the drying time is 6-10 h, and the product is washed 2-4 times with N,N-2-methylformamide.

5. The method for preparing a double-shell hollow porous carbon-supported Ni single-atom catalyst according to claim 1, characterized in that: In the step (5), the concentration of 2-methylimidazole is 20-40 g / L, and the volume ratio of triethylamine to solvent ethanol is 1:600-1:

300.

6. The method for preparing a double-shell hollow porous carbon-supported Ni single-atom catalyst according to claim 1, characterized in that: In the step (6), the reaction time is 30-60 min, the drying temperature is 70-90° C., and the drying time is 10-16 h.

7. A double-shell hollow porous carbon-supported Ni single-atom catalyst prepared according to the method for preparing a double-shell hollow porous carbon-supported Ni single-atom catalyst according to any one of claims 1 to 6.

8. A method for preparing a flow battery cathode, characterized in that: The following steps are involved: The double-shell hollow porous carbon supported Ni single atom catalyst according to claim 7 is dispersed in a mixed solution of ethanol and water, ultrasonicated for 3-8 min to prepare a suspension, added with Nafion adhesive, and then sprayed on carbon paper with a loading of 0.5-1.0 mg / cm -2 , and then placed in a vacuum drying oven at 70°C for 2 h. The carbon paper loaded with the catalyst after drying is the cathode of the flow battery; The volume ratio of ethanol to water is 4:1~9:1, the volume ratio of Nafion binder to suspension is 1:2000~1:1000, and the thickness of carbon paper is 0.21 + 0.01mm.

9. A flow battery, characterized in that: A 0.1-1 mol / L KOH solution or a 0.1-1.0 mol / L KHCO3 solution is used as the electrolyte, the flow battery cathode according to claim 8 is used as the cathode material, and a platinum sheet electrode is used as the anode material.

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