HOF-derived thin-walled carbon nanotube loaded nickel monatomic catalyst and preparation method and application thereof

Abstract

The invention relates to the technical field of electrocatalytic reduction of carbon dioxide, and provides a preparation method of an HOF-derived thin-walled carbon nanotube loaded nickel monatomic catalyst, which comprises the following steps: preparing a Ni-HOF-T precursor; the preparation method comprises the following steps: preparing Ni-HOF-T (at) SiO2; preparing Ni-CNT (at) SiO2; and preparing the HOF-derived thin-walled carbon nanotube loaded nickel monatomic catalyst. The surface of the HOF precursor is coated with a layer of SiO2 armor, so that the pyrolysis behavior of the HOF is improved, and finally, the morphology of the thin-walled carbon nanotube is kept; catalysts with different monatomic coordination structures are constructed through different pyrolysis temperatures, an electron transfer path is optimized, and efficient mass transfer of electrons is promoted, so that the electrocatalytic activity and selectivity of the monatomic catalyst are improved. The invention also discloses an HOF-derived thin-walled carbon nanotube loaded nickel monatomic catalyst and an application thereof.

Description

Technical Field

[0001] The invention belongs to the technical field of electrocatalytic reduction of carbon dioxide, and in particular relates to a HOF-derived thin-walled carbon nanotube-loaded nickel single-atom catalyst and a preparation method and application thereof. Background Art

[0002] At present, with the rapid advancement of industrialization and urbanization, the continuous increase in carbon dioxide (CO2) emissions has triggered a global ecological crisis, such as climate warming, frequent extreme weather, glacier retreat and ocean acidification. These problems not only threaten natural ecosystems, but also pose a severe challenge to the sustainable development of human society. Among the many carbon resource utilization technologies, electrochemical reduction of CO2 (CO2 Reduction Reaction, CO2RR) has attracted widespread attention due to its clean and efficient, mild reaction conditions and the ability to be driven by renewable electricity. However, the promotion of CO2RR technology still faces major challenges. CO2 has a stable molecular structure and low chemical activity, making it difficult to activate. At the same time, the reaction involves a multi-step electron and proton transfer process, which usually requires a high overpotential and is accompanied by competition with the hydrogen evolution reaction, resulting in low selectivity of the target product. In order to achieve efficient conversion of CO2RR, the development of catalysts with excellent activity, selectivity and stability is the core problem and breakthrough direction of current research.

[0003] The highly tunable pore structure and abundant surface active sites of hydrogen-bonded organic frameworks (HOF) and their derivatives give them excellent catalytic performance. In addition, the light weight and highly ordered structure of HOF materials can effectively improve the adsorption capacity of reactants and promote the transfer of charge, making CO2RR a potential template carrier. Single-atom catalysts (SACs) have great application prospects in electrocatalytic CO2 reduction due to their excellent atomic utilization and structural controllability, and by adjusting the coordination environment of single atoms, the activity and selectivity of the catalyst can be significantly improved.

[0004] In order to solve the above technical problems, the present invention designs a HOF-derived thin-walled carbon nanotube-loaded nickel single-atom catalyst and a preparation method and application thereof. Summary of the invention

[0005] The present invention provides a HOF-derived thin-walled carbon nanotube-loaded nickel single-atom catalyst and its preparation method and application. A layer of SiO2 armor is coated on the surface of the HOF precursor, thereby improving the pyrolysis behavior of HOF and ultimately maintaining the morphology of the thin-walled carbon nanotube. Catalysts with different single-atom coordination structures are constructed at different pyrolysis temperatures, optimizing the electron transfer path, promoting efficient mass transfer of electrons, and thus improving the electrocatalytic activity and selectivity of the single-atom catalyst. The catalyst preparation process is simple, the process conditions are easy to control, and it can achieve high selectivity for carbon monoxide in the electrocatalytic reduction of carbon dioxide, while showing a high partial current density.

[0006] To achieve the above-mentioned purpose, the present invention provides the following technical scheme: a method for preparing a HOF-derived thin-walled carbon nanotube-loaded nickel single-atom catalyst, comprising the following steps: S1, preparation of a Ni-HOF-T precursor: mixing deionized water and anhydrous methanol to form a mixed solvent, then dissolving trimesic acid, melamine and nickel chloride hexahydrate in the mixed solvent to obtain a milky white mixed solution; after stirring until uniformly dispersed at room temperature, transferring the mixed solution to a hydrothermal reactor for hydrothermal reaction, cooling to room temperature after the reaction is complete, then washing by centrifugation for several times, and drying in a vacuum oven to finally obtain a white Ni-HOF-T precursor powder; S2, preparation of Ni-HOF-T@SiO2: mixing deionized water and anhydrous methanol to form a mixed solvent, then dissolving the Ni-HOF-T precursor powder obtained in step S1 and tetraethyl silicate in the mixed solvent to obtain a milky white mixed solution. liquid; after being ultrasonically dispersed, the mixed solution is transferred to a hydrothermal reactor for hydrothermal reaction. After the reaction is complete, it is cooled to room temperature, washed by centrifugation for several times, and placed in a vacuum oven to dry, and finally a white Ni-HOF-T@SiO2 powder is obtained; S3, preparation of Ni-CNT@SiO2: the white Ni-HOF-T@SiO2 powder in step S2 is fully ground, placed in a tube furnace and subjected to high-temperature pyrolysis in an inert atmosphere, and cooled to room temperature to obtain a black Ni-CNT@SiO2 powder; S4, HOF-derived thin-walled carbon nanotube-loaded nickel single-atom catalyst: the Ni-CNT@SiO2 powder obtained in step S3 is ground and added to a hydrofluoric acid solution for pickling. After removing SiO2, it is washed by centrifugation for several times with deionized water and anhydrous ethanol, and placed in a vacuum oven to dry, and finally a HOF-derived thin-walled carbon nanotube-loaded nickel single-atom catalyst is obtained.

[0007] Based on the above technical solution, the volume ratio of deionized water to anhydrous methanol in the mixed solvent in steps S1 and S2 is (1-2):(1-4), the molar ratio of trimesic acid to melamine in step S1 is 1:1, and the molar ratio of melamine to nickel chloride hexahydrate is (1-4):1.

[0008] Based on the above technical scheme, the hydrothermal temperature in steps S1 and S2 is 120-150°C; the hydrothermal time is 12-24h, the washing solvent is methanol or ethanol, the washing times are 3-6 times, the vacuum drying temperature is 50-80°C, and the time is 8-24h.

[0009] Based on the above technical solution, in step S2, the mass ratio of Ni-HOF-T precursor powder to tetraethyl silicate is 1:(5-10), and the ultrasonic treatment time is 15-45 min.

[0010] Based on the above technical solution, in step S3, the pyrolysis temperature is 800-1100° C., the pyrolysis atmosphere is argon atmosphere, and the pyrolysis time is 2-3 hours.

[0011] Based on the above technical solution, the concentration range of the hydrofluoric acid solution in step S4 is 12% to 48%.

[0012] Based on the above technical solution, in step S4, the pickling time is 12 to 48 hours, the washing solvent is methanol or ethanol, the washing times are 3 to 6 times, the vacuum drying temperature is 50 to 80° C., and the time is 8 to 24 hours.

[0013] In a second aspect, the present invention provides a HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst, which is prepared according to the preparation method of the HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst described in any one of the above embodiments.

[0014] In a third aspect, the present invention provides the use of a HOF-derived thin-walled carbon nanotube-loaded nickel single-atom catalyst prepared by the preparation method of a HOF-derived thin-walled carbon nanotube-loaded nickel single-atom catalyst described in any one of the above embodiments in the electroreduction of carbon dioxide to generate carbon monoxide.

[0015] Based on the above technical solution, the voltage applied in the process of electroreduction of carbon dioxide to produce carbon monoxide is in the range of -0.45 to -1.0 V (vs. RHE).

[0016] Compared with the related art, the beneficial effects of the present invention are as follows: 1. The present invention is based on hydrogen-bonded organic framework materials and uses a silicon dioxide-mediated HOF template method to prepare a thin-walled N-doped carbon nanotube catalyst loaded with Ni single atoms. The synthesis process is simple, easy to operate, and easy to promote and use; 2. The HOF-derived thin-walled carbon nanotubes obtained by the present invention are loaded with nickel single-atom catalysts, and nickel and nitrogen are coordinated to form catalytic active sites. The tube walls are ultra-thin, the skeleton is stable, and the pores are rich, which helps to increase the exposure of the active sites and can catalyze the electroreduction of carbon dioxide to produce carbon monoxide with high activity and high selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] 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 prior art descriptions are briefly introduced below. Obviously, the drawings described below are only one embodiment of the present invention, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0018] Figure 1 It is a schematic diagram of the preparation process of the HOF-derived thin-walled carbon nanotube-loaded nickel single-atom catalyst provided by the present invention.

[0019] Figure 2 It is the X-ray diffraction pattern of the HOF-T precursor prepared in Examples 1-3 of the present invention and Comparative Example 1.

[0020] Figure 3 1 is a scanning electron microscope image of the HOF-T precursors prepared in Examples 1-3 of the present invention and Comparative Example 1, wherein (a) Ni0-HOF-T precursor; (b) Ni 0.3 -HOF-T precursor; (c) Ni 0.5 -HOF-T precursor; (d) Ni 0.7 -HOF-T precursor.

[0021] Figure 4 3 is a nitrogen adsorption isotherm diagram of the HOF-T precursor prepared in Example 1 of the present invention and Comparative Example 1.

[0022] Figure 5 It is the pore size distribution diagram of the HOF-T precursor prepared in Example 1 of the present invention and Comparative Example 1.

[0023] Figure 6 It is the X-ray diffraction pattern of the HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst prepared in Examples 1-5 and Comparative Example 1 of the present invention.

[0024] Figure 7 It is the Raman spectrum of the HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst prepared in Examples 1-5 of the present invention and Comparative Example 1.

[0025] Figure 8 is a scanning electron microscope image of the HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst obtained in Example 2 and Example 4 of the present invention, wherein (a) Ni 0.5 -CNT-1000-SACs; (b)Ni 0.5 -CNT-900-SACs.

[0026] Fig. 9It is a nitrogen adsorption isotherm diagram of the HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst prepared in Examples 2, 4, and 5 of the present invention.

[0027] Fig.10 This is a pore size distribution diagram of the HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst prepared in Examples 2, 4, and 5 of the present invention.

[0028] Fig.11 It is a linear sweep voltammetric characteristic curve (LSV) diagram of carbon dioxide electroreduction of HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalysts prepared in Examples 1-5 of the present invention and Comparative Example 1 in an H-type electrolytic cell.

[0029] Fig.12 It is a bar graph of the Faraday efficiency (FE) of the HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst prepared in Examples 1-5 of the present invention and Comparative Example 1 for the electroreduction of carbon dioxide to carbon monoxide in an H-type electrolytic cell.

[0030] Fig.13 It is a graph of the partial current density of the HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst prepared in Examples 1-5 of the present invention and Comparative Example 1 for the electroreduction of carbon dioxide to carbon monoxide in an H-type electrolytic cell. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with the accompanying drawings and examples: Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0032] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] In the description of the present invention, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0034] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0035] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0036] Combination Figure 1 As shown, the present invention provides a method for preparing a HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst, comprising the following steps: S1, preparation of Ni-HOF-T precursor: deionized water and anhydrous methanol are mixed to form a mixed solvent, and then trimesic acid, melamine and nickel chloride hexahydrate are dissolved in the mixed solvent to obtain a milky white mixed solution; after stirring at room temperature until uniformly dispersed, the mixed solution is transferred to a hydrothermal reactor for hydrothermal reaction, and after the reaction is complete, it is cooled to room temperature, washed by centrifugation for several times, and placed in a vacuum oven to dry, and finally a white Ni-HOF-T precursor powder is obtained; S2, preparation of Ni-HOF-T@SiO2: deionized water and anhydrous methanol are mixed to form a mixed solvent, and then the Ni-HOF-T precursor powder obtained in step S1 and tetraethyl silicate are dissolved in the mixed solvent to obtain a milky white mixed solution; after being uniformly dispersed by ultrasonication, the mixed solution is transferred to a hydrothermal reactor for hydrothermal reaction, and after the reaction is complete, it is cooled to room temperature, washed by centrifugation for several times, and placed in a vacuum oven for drying to finally obtain white Ni-HOF-T@SiO2 powder; S3, preparation of Ni-CNT@SiO2: the white Ni-HOF-T@SiO2 powder in step S2 is fully ground, placed in a tube furnace and subjected to high-temperature pyrolysis in an inert atmosphere, and cooled to room temperature to obtain black Ni-CNT@SiO2 powder; S4, HOF-derived thin-walled carbon nanotube-loaded nickel single-atom catalyst: grind the Ni-CNT@SiO2 powder obtained in step S3 and add it to a hydrofluoric acid solution for pickling. After removing SiO2, wash it with deionized water and anhydrous ethanol by centrifugation for several times, and dry it in a vacuum oven to finally obtain a HOF-derived thin-walled carbon nanotube-loaded nickel single-atom catalyst.

[0037] Based on the above technical solution, the volume ratio of deionized water to anhydrous methanol in the mixed solvent in steps S1 and S2 is (1-2): (1-4), the molar ratio of trimesic acid to melamine in step S1 is 1:1, and the molar ratio of melamine to nickel chloride hexahydrate is (1-4): 1. Preferably, the volume ratio of deionized water to anhydrous methanol is 1:1.

[0038] Based on the above technical solution, the hydrothermal temperature in steps S1 and S2 is 120-150°C; the hydrothermal time is 12-24h, the washing solvent is methanol or ethanol, the washing times are 3-6 times, the vacuum drying temperature is 50-80°C, and the time is 8-24h. Preferably, the hydrothermal temperature is 150°C, the hydrothermal time is 12h, the washing solvent is methanol, the washing times are 3 times, the vacuum drying temperature is 60°C, and the time is 12h.

[0039] Based on the above technical solution, in step S2, the mass ratio of Ni-HOF-T precursor powder to tetraethyl silicate is 1:(5-10), and the ultrasonic treatment time is 15-45 min. Preferably, the mass ratio of Ni-HOF-T precursor powder to tetraethyl silicate is 1:8, and the ultrasonic treatment time is 30 min.

[0040] Based on the above technical solution, in step S3, the pyrolysis temperature is 800-1100° C., the pyrolysis atmosphere is argon atmosphere, and the pyrolysis time is 2-3 hours. Preferably, the pyrolysis time is 2 hours.

[0041] Based on the above technical solution, the concentration of the hydrofluoric acid solution in step S4 ranges from 12% to 48%. Preferably, the concentration of the hydrofluoric acid solution is 12%.

[0042] Based on the above technical solution, in step S4, the pickling time is 12 to 48 hours, the washing solvent is methanol or ethanol, the washing times are 3 to 6 times, the vacuum drying temperature is 50 to 80°C, and the time is 8 to 24 hours. Preferably, the pickling time is 24 hours, the washing solvent is methanol, the washing times are 3 times, the vacuum drying temperature is 60°C, and the time is 12 hours.

[0043] In a second aspect, the present invention provides a HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst, which is prepared according to the preparation method of the HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst described in any one of the above embodiments.

[0044] In a third aspect, the present invention provides the use of a HOF-derived thin-walled carbon nanotube-loaded nickel single-atom catalyst prepared by the preparation method of a HOF-derived thin-walled carbon nanotube-loaded nickel single-atom catalyst described in any one of the above embodiments in the electroreduction of carbon dioxide to generate carbon monoxide.

[0045] Based on the above technical solution, the voltage applied in the process of electroreduction of carbon dioxide to produce carbon monoxide is in the range of -0.45 to -1.0 V (vs. RHE).

[0046] The present invention coats a layer of SiO2 armor on the surface of the HOF precursor, thereby improving the pyrolysis behavior of HOF and ultimately maintaining the morphology of thin-walled carbon nanotubes; different catalysts with single-atom coordination structures are constructed at different pyrolysis temperatures, optimizing the electron transfer path, promoting efficient mass transfer of electrons, and thus improving the electrocatalytic activity and selectivity of the single-atom catalyst. The catalyst preparation process is simple, the process conditions are easy to control, and it can achieve high selectivity for carbon monoxide in the electrocatalytic reduction of carbon dioxide, while showing a higher partial current density.

[0047] Example 1 This embodiment provides a method for preparing a HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst, comprising the following steps: S1, 35ml of deionized water and 35ml of anhydrous methanol were mixed as solvents, 0.72mmol of nickel chloride hexahydrate, 2.4mmol of melamine and 2.4mmol of trimesic acid were added in sequence and dissolved in the mixed solvent to obtain a milky white mixed solution. After sufficient stirring, the mixed solution was transferred to a hydrothermal reactor and subjected to a hydrothermal reaction at 150°C for 12h. After cooling to room temperature, it was transferred to a centrifuge tube and washed three times by centrifugation with anhydrous methanol, and then placed in a vacuum drying oven at 60°C for 12h to obtain white Ni 0.3 -HOF-T precursor powder; S2, 35 ml of deionized water and 35 ml of anhydrous methanol were mixed as solvent, and then 500 mg of Ni obtained in step S1 was added. 0.3 -HOF-T precursor powder and 4g tetraethyl silicate were dissolved in a mixed solvent to obtain a milky white mixed solution; after ultrasonication for 30min, the mixed solution was transferred to a hydrothermal reactor and subjected to a hydrothermal reaction at 150°C for 12h. After cooling to room temperature, the mixed solution was transferred to a centrifuge tube and washed three times by centrifugation with anhydrous ethanol, and then placed in a vacuum drying oven at 60°C for 12h to obtain a white Ni 0.3 -HOF-T@SiO2 powder; S3, the white Ni in step S2 0.3 -HOF-T@SiO2 powder was fully ground and placed in a tube furnace protected by argon atmosphere at 1000℃ for 2h. After cooling to room temperature, black Ni 0.3 -CNT-1000@SiO2 powder; S4, the Ni obtained in step S3 0.3 After grinding, CNT@SiO2 powder was added to 12% hydrofluoric acid solution for pickling for 24 h. After removing SiO2, it was centrifugally washed three times with deionized water and anhydrous ethanol, and dried in a vacuum drying oven at 60 °C for 12 h. Finally, HOF-derived thin-walled carbon nanotubes loaded with nickel single atom catalyst Ni 0.3 -CNT-1000-SACs.

[0048] Example 2 The preparation method of this embodiment is the same as that of embodiment 1, and the same parts are omitted. The difference from embodiment 1 is that in this embodiment, the amount of nickel chloride hexahydrate added in step S1 is 1.2 mmol, and finally HOF-derived thin-walled carbon nanotube-supported nickel single atom catalyst Ni 0.5 -CNT-1000-SACs.

[0049] Example 3 The preparation method of this embodiment is the same as that of embodiment 1, and the same parts are omitted. The difference from embodiment 1 is that in this embodiment, the amount of nickel chloride hexahydrate added in step S1 is 1.68 mmol, and finally HOF-derived thin-walled carbon nanotube-supported nickel single atom catalyst Ni 0.7 -CNT-1000-SACs.

[0050] Example 4 The preparation method of this embodiment is the same as that of embodiment 2, and the same parts are omitted. The difference from embodiment 1 is that in this embodiment, the pyrolysis temperature of the tube furnace in step S3 is 900° C., and finally HOF-derived thin-walled carbon nanotubes loaded with nickel single atom catalyst Ni 0.5 -CNT-900-SACs.

[0051] Example 5 The preparation method of this embodiment is the same as that of embodiment 2, and the same parts are omitted. The difference from embodiment 1 is that in this embodiment, the tube furnace pyrolysis temperature in step S3 is 1100° C., and finally HOF-derived thin-walled carbon nanotubes loaded with nickel single atom catalyst Ni 0.5 -CNT-1100-SACs.

[0052] Comparative Example 1 The preparation method of this comparative example is the same as that of Example 1, and the same parts are omitted. The difference from Example 1 is that in this comparative example, nickel chloride hexahydrate is not added in step S1, and finally HOF-derived thin-walled carbon nanotube-loaded nickel single-atom catalyst Ni0-CNT-1000-SACs is obtained.

[0053] Example 6 The HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst prepared in Examples 1-5 of the present invention and Comparative Example 1 was used to test the carbon dioxide electroreduction performance.

[0054] The carbon dioxide electroreduction performance test was carried out using a three-electrode system, with carbon paper loaded with HOF-derived thin-walled carbon nanotubes loaded with nickel single-atom catalysts prepared in Examples 1-5 and Comparative Example 1 as the working electrode, a saturated silver / silver chloride electrode as the reference electrode, and a platinum electrode as the counter electrode. Potassium bicarbonate solution was used as the electrolyte, and an H-type electrolytic cell was used. A constant potential test was performed. Before the test, carbon dioxide gas was introduced to saturate the electrolyte, and the flow rate of CO2 was maintained at , time is 30min. The potential range of the test process is The gas phase products produced by the reaction are detected by gas chromatograph, and the liquid phase products are detected by nuclear magnetic resonance hydrogen spectrometer, and the Faraday efficiency is calculated based on them.

[0055] Figure 1 The present invention is a flow chart of preparing HOF-derived thin-walled carbon nanotube-loaded nickel single-atom catalyst.

[0056] Figure 2 The X-ray diffraction patterns of the HOF-T precursors prepared in Examples 1-3 of the present invention and Comparative Example 1 show that different molar ratios of the metal nickel source nickel chloride hexahydrate and the melamine ligand do not change the crystal structure of the HOF-T precursor, and a HOF-T precursor with sharp crystal shape and good crystallinity can be obtained.

[0057] Figure 3 The scanning electron microscope images of the HOF-T precursors prepared in Examples 1-3 of the present invention and Comparative Example 1 show that different molar ratios of the metal nickel source nickel chloride hexahydrate and the melamine ligand do not change the morphological characteristics of the HOF-T precursor, and uniform HOF-T nanotubes can be obtained.

[0058] Figure 4 and Figure 5 The nitrogen adsorption isotherms and pore size distribution diagrams of the HOF-T precursors prepared in Example 1 and Comparative Example 1 are shown respectively. It is shown that the HOF-T precursors containing nickel and those without nickel have mixed pore structures. It can be confirmed that the pore structure is mainly mesopores, and the size of the mesopores is about 2.5 nm. In addition, the specific surface area of ​​the sample can be calculated by the BET model. Ni 0.5 -HOF-T showed a significant increase in specific surface area compared to Ni0-HOF-T, indicating that the introduction of metal atoms can effectively increase the specific surface area of ​​the material.

[0059] Figure 6 The X-ray diffraction patterns of the HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalysts prepared in Examples 1-5 and Comparative Example 1 of the present invention are shown in Table 1. In the X-ray diffraction patterns, the catalysts prepared in Examples 1-5 and Comparative Example 1 have only about Two broad peaks appeared at , corresponding to the (002) and (101) crystal planes of graphite carbon, indicating that the obtained catalyst had a high degree of carbonization. No diffraction peak of Ni species was detected, indicating that the Ni species was amorphous, confirming that Ni existed in a single atomic form.

[0060] Figure 7 The Raman spectra of the HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalysts prepared in Examples 1-5 and Comparative Example 1 of the present invention are shown in Figure 1. In the spectra, the catalysts prepared in Examples 1-5 and Comparative Example 1 have only a Raman peak at about 1580 cm -1 and 1350cm -1 Two broad peaks appeared at , corresponding to the G peak and D peak of graphite carbon. The intensity ratios of the D peak and the G peak in Examples 1-5, ID / IG, were all less than 1, indicating that the introduction of nickel element can improve the graphitization degree of the material to improve the conductivity.

[0061] Figure 8 The scanning electron microscope images of the HOF-derived thin-walled carbon nanotubes loaded with nickel single-atom catalysts obtained in Examples 2 and 4 of the present invention show the protective effect of the silica armor, and different pyrolysis temperatures do not change the morphological characteristics of the derived carbon materials, and the morphology of the thin-walled carbon nanotubes is still maintained.

[0062] Fig. 9 and Fig.10 The nitrogen adsorption isotherms and pore size distribution diagrams of the HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalysts prepared in Examples 2, 4, and 5 of the present invention are shown. 0.5 -CNT-900-SACs, Ni 0.5 -CNT-1000-SACs, Ni 0.5 The pore structures of the three samples of CNT-1100-SACs are mainly micropores. 0.5 -CNT-1000-SACs have a large specific surface area, which is conducive to the contact between the surface sites of the material and the surrounding environment and the transmission of substances.

[0063] Fig.11 The linear sweep voltammetric characteristic curve (LSV) of the HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst prepared in Examples 1-5 of the present invention and Comparative Example 1 for carbon dioxide electroreduction in an H-type electrolytic cell. 0.5 -CNT-1000-SACs showed the lowest onset potential in CO2-saturated electrolyte, indicating that 0.5 -CO2RR on CNT-1000-SACs has the lowest reaction energy barrier and the highest catalytic activity, which is beneficial to improve the energy efficiency of the cathode reaction.

[0064] Fig.12The Faraday efficiency bar graph of the HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst prepared in Examples 1-5 of the present invention and Comparative Example 1 for the electroreduction of carbon dioxide to carbon monoxide in an H-type electrolytic cell. 0.5 -CNT-1000-SACs achieved a Faradaic efficiency of more than 90% for carbon monoxide products in a wide potential range of -0.7~-1.0V vs.RHE, and a Faradaic efficiency of up to 98% at -0.75V vs.RHE, which is higher than that of other embodiments, and has extremely excellent selectivity for CO products.

[0065] Fig.13 The graph is a partial current density curve of the electroreduction of carbon dioxide to carbon monoxide in an H-type electrolytic cell using the HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst prepared in Examples 1-5 of the present invention and Comparative Example 1. 0.5 -CNT-1000-SACs has the largest partial current density, which is greater than that of other embodiments and has the best catalytic performance.

[0066] In summary, the HOF-derived thin-walled carbon nanotubes loaded with nickel single-atom catalysts prepared in the present invention have ultra-thin tube walls, stable skeletons, and abundant pores, which help to increase the exposure of active sites and can catalyze the electroreduction of carbon dioxide to produce carbon monoxide with high activity and selectivity.

[0067] The present invention is described above by way of examples, but the present invention is not limited to the above specific embodiments, and any changes or modifications made based on the present invention belong to the scope of protection claimed by the present invention.

Claims

1. A method for preparing a HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst, characterized in that: The following steps are involved: S1, preparation of Ni-HOF-T precursor: deionized water and anhydrous methanol are mixed to form a mixed solvent, and then trimesic acid, melamine and nickel chloride hexahydrate are dissolved in the mixed solvent to obtain a milky white mixed solution; after stirring at room temperature until uniformly dispersed, the mixed solution is transferred to a hydrothermal reactor for hydrothermal reaction, and after the reaction is complete, it is cooled to room temperature, washed by centrifugation for several times, and placed in a vacuum oven to dry, and finally a white Ni-HOF-T precursor powder is obtained; S2, preparation of Ni-HOF-T@SiO2: deionized water and anhydrous methanol are mixed to form a mixed solvent, and then the Ni-HOF-T precursor powder obtained in step S1 and tetraethyl silicate are dissolved in the mixed solvent to obtain a milky white mixed solution; after being uniformly dispersed by ultrasonication, the mixed solution is transferred to a hydrothermal reactor for hydrothermal reaction, and after the reaction is complete, it is cooled to room temperature, washed by centrifugation for several times, and placed in a vacuum oven for drying to finally obtain white Ni-HOF-T@SiO2 powder; S3, preparation of Ni-CNT@SiO2: the white Ni-HOF-T@SiO2 powder in step S2 is fully ground, placed in a tube furnace and subjected to high-temperature pyrolysis in an inert atmosphere, and cooled to room temperature to obtain black Ni-CNT@SiO2 powder; S4, HOF-derived thin-walled carbon nanotube-loaded nickel single-atom catalyst: grind the Ni-CNT@SiO2 powder obtained in step S3 and add it to a hydrofluoric acid solution for pickling. After removing SiO2, wash it with deionized water and anhydrous ethanol by centrifugation for several times, and dry it in a vacuum oven to finally obtain a HOF-derived thin-walled carbon nanotube-loaded nickel single-atom catalyst.

2. The method for preparing the HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst according to claim 1, characterized in that: The volume ratio of deionized water to anhydrous methanol in the mixed solvent in steps S1 and S2 is (1-2):(1-4), the molar ratio of trimesic acid to melamine in step S1 is 1:1, and the molar ratio of melamine to nickel chloride hexahydrate is (1-4):

1.

3. The method for preparing the HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst according to claim 1, characterized in that: In the steps S1 and S2, the hydrothermal temperature is 120-150° C., the hydrothermal time is 12-24 hours, the washing solvent is methanol or ethanol, the washing times are 3-6 times, the vacuum drying temperature is 50-80° C., and the time is 8-24 hours.

4. The method for preparing the HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst according to claim 1, characterized in that: In step S2, the mass ratio of Ni-HOF-T precursor powder to tetraethyl silicate is 1:(5-10), and the ultrasonic treatment time is 15-45 minutes.

5. The method for preparing the HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst according to claim 1, characterized in that: In step S3, the pyrolysis temperature is 800-1100° C., the pyrolysis atmosphere is an argon atmosphere, and the pyrolysis time is 2-3 hours.

6. The method for preparing the HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst according to claim 1, characterized in that: The concentration of the hydrofluoric acid solution in step S4 is in the range of 12% to 48%.

7. The method for preparing the HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst according to claim 1, characterized in that: In step S4, the pickling time is 12 to 48 hours, the washing solvent is methanol or ethanol, the washing times are 3 to 6 times, the vacuum drying temperature is 50 to 80° C., and the time is 8 to 24 hours.

8. A HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst, characterized in that: The method for preparing the HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst according to any one of claims 1 to 7.

9. Use of the HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst prepared by the preparation method of the HOF-derived thin-walled carbon nanotube-supported nickel single-atom catalyst according to any one of claims 1 to 7 in the electroreduction of carbon dioxide to generate carbon monoxide.

10. The use according to claim 9, characterized in that: The voltage applied in the process of electroreduction of carbon dioxide to produce carbon monoxide is in the range of -0.45 to -1.0 V (vs. RHE).

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