Preparation Method and Application of Zinc Single-Atom Loaded Porous Carbon Nanotubes

Abstract

The present invention discloses a preparation method and application of zinc single-atom loaded porous carbon nanotubes. The preparation method is as follows: Sodium tellurite is dissolved in an aqueous solution of polyvinylpyrrolidone, and then ammonia water and hydrazine hydrate are added. Tellurium nanowires are generated by a one-step hydrothermal method. After separating the tellurium nanowires, they are dissolved in deionized water to obtain an aqueous solution of tellurium nanowires; Glucosamine as a carbon source and zinc nitrate as a metal source are added to the aqueous solution of tellurium nanowires, stirred evenly, and then subjected to a hydrothermal reaction. The obtained black complex is freeze-dried to obtain a black aerogel, and after being subjected to high-temperature calcination treatment and cooled to room temperature, zinc single-atom loaded porous carbon nanotubes can be obtained. The porous carbon nanotubes prepared by the present invention not only have the advantages of large specific surface area, good conductivity, strong permeability, high temperature resistance, etc., but also have atomically dispersed Zn-N-C highly active sites to drive the oxygen reduction reaction, and can be used as a cathode oxygen reduction electrocatalyst in alkaline electrolytes and an air cathode catalyst in zinc-air batteries.

Description

Technical Field

[0001] The present invention relates to a preparation method and application of porous carbon nanotubes, and particularly to a preparation method and application of zinc single-atom loaded porous carbon nanotubes. Background Art

[0002] The oxygen reduction reaction (ORR) plays a crucial role in various energy conversion and storage systems, such as fuel cells and metal-air batteries. Atomically dispersed transition metal (M) and nitrogen co-doped carbon materials (M-N-C) are promising platinum-free ORR catalysts, in which transition metal and nitrogen atoms can induce charge distribution, thereby improving the adsorption and reduction behavior of O 2 . The best-developed M-N-C catalysts currently have high initial activity and turnover frequency comparable to Pt / C, but their practical application is hindered due to their unsatisfactory physical and chemical stability. In addition, the reported transition metal sources are mainly limited to Fe, Co, Ni, and Mn. Studies have shown that the intermediate valence states of these transition metals, as well as the residues of some incompletely coordinated ions, will damage the stability of the electrode and electrolyte membrane during the ORR process. Compared with Fe, Co, Ni, and Mn, the d orbitals (3d 10 4s 2 ) of Zn element are completely filled and cannot form higher-valent oxidation ions. Therefore, Zn-N-C catalysts are expected to have no harmful effects on the electrode and electrolyte membrane. However, the reported Zn-N-C catalysts have lower catalytic performance in ORR than Fe-N-C catalysts, probably because Zn precursors are highly volatile and easily removed during high-temperature pyrolysis, resulting in a low density of active sites. Some recent experimental and computational studies have shown that M-N 4 sites with axial ligands (XA, such as OH, Cl, F, Br) can improve ORR catalytic activity. However, these axial ligands are bonded to the M-N 4 sites through ionic bonds, and the axial ligands are prone to fall off during the ORR catalytic process. Therefore, achieving stable axial charge redistribution on a limited number of Zn-N 4 sites to improve its intrinsic activity has important practical significance for the practical application of Zn-N-C catalysts. Summary of the Invention

[0003] Object of the Invention: The present invention aims to provide a preparation method of zinc single-atom loaded porous carbon nanotubes with high electrochemical activity and stability; another object of the present invention is to provide the application of the catalyst prepared by this method in cathodic oxygen reduction electrocatalysis in alkaline electrolyte and as an air cathode catalyst in zinc-air batteries.

[0004] Technical Solution: The preparation method of the zinc single-atom loaded porous carbon nanotubes described in the present invention is as follows:

[0005] Using polyvinylpyrrolidone (PVP) as a surfactant and sodium tellurite in a mixed solution of ammonia water and hydrazine hydrate, tellurium nanowires are generated by a one-step hydrothermal method. After separating the tellurium nanowires with acetone, they are dissolved in water to obtain an aqueous solution of tellurium nanowires. Then, carbon source glucosamine and metal source zinc nitrate are added to the aqueous solution of tellurium nanowires and stirred evenly, followed by hydrothermal reaction. The obtained black complex is freeze-dried to obtain a black aerogel, and after high-temperature calcination treatment and cooling to room temperature, zinc single-atom loaded porous carbon nanotubes can be obtained.

[0006] The specific steps are as follows:

[0007] (1) Synthesize an aqueous solution of tellurium nanowires: Dissolve sodium tellurite in an aqueous solution of polyvinylpyrrolidone (PVP) and stir evenly. Then add ammonia water and hydrazine hydrate thereto and continue to stir at room temperature to form a uniform mixed solution. A precipitate complex is formed by a one-step hydrothermal method. After separating the tellurium nanowires with acetone, they are dissolved in water to form an aqueous solution of tellurium nanowires;

[0008] (2) Synthesize an intermediate product: Use zinc nitrate as the metal source and glucosamine as the carbon source, add them to the aqueous solution of tellurium nanowires obtained in step (1), stir at room temperature to dissolve them fully, and obtain a black complex by hydrothermal method. After cooling, it is freeze-dried to obtain a black aerogel;

[0009] (3) Prepare zinc single-atom loaded porous carbon nanotubes: Heat-treat the black solid obtained in step (2) in an inert atmosphere by programmed heating to 800 °C - 1000 °C, and then cool it to obtain the final product - zinc single-atom loaded porous carbon nanotubes.

[0010] In the present invention, a black complex adsorbed with Zn(II) on the surface is pre-generated by a simple one-step hydrothermal synthesis method, and then zinc single-atom loaded porous carbon nanotubes are prepared through freeze-drying and high-temperature calcination, which not only effectively improves the catalytic activity of the catalyst but also endows the catalyst with extremely high structural stability.

[0011] Preferably, in step (1), the hydrothermal temperature in the hydrothermal method is 160 °C - 200 °C, and the hydrothermal time is 3 - 4 h.

[0012] Preferably, in step (2), the hydrothermal temperature in the hydrothermal method is 160 °C - 200 °C, the hydrothermal time is 12 - 18 h; the input molar amount of zinc nitrate is 1 - 4 mmol.

[0013] Preferably, the inert atmosphere in step (3) is one or more mixtures of nitrogen, helium, or argon.

[0014] Preferably, the heating rate in step (3) is 0.5 - 10 °C·min -1, the heat treatment time is 1 to 3 h.

[0015] The material prepared by the method for preparing zinc single-atom-loaded porous carbon nanotubes of the present invention is used as a catalyst for oxygen reduction at the cathode of a fuel cell in an alkaline electrolyte.

[0016] The material prepared by the method for preparing zinc single-atom-loaded porous carbon nanotubes of the present invention is used as an air cathode catalyst in a zinc-air battery.

[0017] In the method of the present invention, sodium tellurite is used as the metal source, and polyvinylpyrrolidone is used as the surfactant. Tellurium nanowires are pre-coordinated and complexed to generate tellurium nanowires, and then glucose amine is fully coated on its surface to adsorb Zn(II). After freeze-drying and high-temperature carbonization and self-reduction in an inert atmosphere, zinc single-atom-loaded porous carbon nanotubes can be prepared. This method is simple and easy to operate, and the raw material cost is low, and large-scale production can be realized. The zinc single-atom-loaded porous carbon nanotubes prepared by the present invention have the advantages of large specific surface area, good electrical conductivity, strong permeability, high temperature resistance, etc.; and at the same time, they have atomically dispersed Zn-N-C highly active sites to drive the oxygen reduction reaction. As a cathode oxygen reduction catalyst under alkaline conditions, it exhibits higher electrocatalytic activity and stability than commercial Pt / C, and also exhibits higher energy conversion efficiency and stronger charge-discharge cycle stability in zinc-air batteries.

[0018] The zinc single-atom-loaded porous carbon nanotube catalyst prepared in the present invention has the following advantages: ① The one-dimensional porous carbon nanotube structure is beneficial to mass transfer during the electrocatalytic reaction. At the same time, the doping of N elements is beneficial to improving the graphitization degree of the carbon carrier and improving the electronic structure of the carbon carrier to provide more active sites; ② Synchrotron radiation test results show that the coordination environment of the synthesized Zn-N-C material is Zn-N 5 -C. The special axial coordination can induce electron redistribution and improve the intrinsic activity; ③ Atomically dispersed metal active sites avoid aggregation and dissolution during the catalytic reaction, thereby improving its anti-sintering performance and electrochemical stability.

[0019] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages: (1) The zinc single atoms of the porous carbon nanotube catalyst prepared by the preparation method are uniformly embedded in the porous carbon nanotubes. When used as a catalyst, it is highly efficient, stable, and has a long service life; compared with the commercial 20% Pt / C catalyst, the prepared porous carbon nanotubes loaded with zinc single atoms have more excellent oxygen reduction electrocatalytic performance and stability in alkaline electrolytes, and are a very promising substitute for platinum-based catalysts, with broad application prospects in the future energy industry; (2) The preparation method prepares the porous carbon nanotube catalyst loaded with zinc single atoms by a simple and scalable high-temperature carbothermal reduction method. The raw materials such as polyvinylpyrrolidone and glucosamine used are cheap and easily available, the reaction conditions are easy to control, the equipment is simple, and large-scale production can be achieved. Description of the Drawings

[0020] Figure 1 It is the transmission electron microscope (TEM) image of the porous carbon nanotubes loaded with zinc single atoms prepared in Example 1;

[0021] Figure 2 It is the scanning electron microscope (SEM) image of the porous carbon nanotubes loaded with zinc single atoms prepared in Example 1;

[0022] Figure 3 It is the aberration-corrected scanning transmission electron microscope (AC-STEM) image of the porous carbon nanotubes loaded with zinc single atoms prepared in Example 1;

[0023] Figure 4 It is the X-ray diffraction (XRD) pattern of the porous carbon nanotubes loaded with zinc single atoms prepared in Example 1;

[0024] Figure 5 It is the oxygen electrocatalytic reduction (ORR) curve of the porous carbon nanotubes loaded with zinc single atoms prepared in Example 1 compared with the commercial 20% Pt / C;

[0025] Figure 6 It is the stability chronoamperometry test curve of the porous carbon nanotubes loaded with zinc single atoms prepared in Example 1 compared with the porous Pt / C framework and the commercial 20% Pt / C;

[0026] Figure 7 It is the charge-discharge curve of the zinc-air battery assembled with the porous carbon nanotubes loaded with zinc single atoms prepared in Example 1 as the air cathode under the condition of a constant current density of 5 mA cm -2 Condition. Detailed Embodiments

[0027] The technical solutions of the present invention will be further described below with reference to the drawings.

[0028] Example 1

[0029] Preparation method of zinc single-atom loaded porous carbon nanotubes, comprising the following steps:

[0030] 1) Preparation of tellurium nanowire aqueous solution: Weigh 0.5 g of polyvinylpyrrolidone and dissolve it in 25 mL of deionized water, add 0.095 g of sodium tellurite, stir to form a homogeneous solution, then add 1.65 mL of hydrazine hydrate and 3.35 mL of ammonia water thereto, continue stirring for 30 min, and then put the mixed solution into an oven at 180 °C for hydrothermal treatment for 3.5 h. After the hydrothermal treatment is completed and it is cooled, separate the tellurium nanowire solid with acetone, and dissolve it in 50 mL of deionized water to form a tellurium nanowire aqueous solution;

[0031] 2) Synthesis of intermediate product: Weigh 2 mmol of zinc nitrate and 0.5 g of glucosamine, dissolve them in 25 mL of the above-prepared tellurium nanowire solution, stir for 1 h, and then put the mixed solution into an oven at 180 °C for hydrothermal treatment for 15 h. After the hydrothermal treatment is completed and it is cooled, obtain a black aerogel through freeze-drying;

[0032] 3) Preparation of zinc single-atom loaded porous carbon nanotubes: Heat-treat the black aerogel prepared in step 2) in a nitrogen atmosphere at a programmed heating rate of 3 °C / min -1 Raise the temperature to 900 °C, hold at this temperature for 2 h, and then cool to obtain zinc single-atom loaded porous carbon nanotubes.

[0033] Example 2

[0034] Preparation method of zinc single-atom loaded porous carbon nanotubes, comprising the following steps:

[0035] 1) Preparation of tellurium nanowire aqueous solution: Weigh 0.5 g of polyvinylpyrrolidone and dissolve it in 25 mL of deionized water, add 0.095 g of sodium tellurite, stir to form a homogeneous solution, then add 1.65 mL of hydrazine hydrate and 3.35 mL of ammonia water thereto, continue stirring for 30 min, and then put the mixed solution into an oven at 160 °C for hydrothermal treatment for 3.5 h. After the hydrothermal treatment is completed and it is cooled, separate the tellurium nanowire solid with acetone, and dissolve it in 50 mL of deionized water to form a tellurium nanowire aqueous solution;

[0036] 2) Synthesis of intermediate product: Weigh 2 mmol of zinc nitrate and 0.5 g of glucosamine, dissolve them in 25 mL of the above-prepared tellurium nanowire solution, stir for 1 h, and then put the mixed solution into an oven at 180 °C for hydrothermal treatment for 15 h. After the hydrothermal treatment is completed and it is cooled, obtain a black aerogel through freeze-drying;

[0037] 3) Preparation of zinc single-atom loaded porous carbon nanotubes: Heat-treat the black aerogel prepared in step 2) in a nitrogen atmosphere at a programmed heating rate of 3 °C / min -1 Raise the temperature to 900 °C, hold at this temperature for 2 h, and then cool to obtain zinc single-atom loaded porous carbon nanotubes.

[0038] Example 3

[0039] A method for preparing zinc single-atom loaded porous carbon nanotubes, comprising the following steps:

[0040] 1) Preparation of tellurium nanowire aqueous solution: Weigh 0.5 g of polyvinylpyrrolidone and dissolve it in 25 mL of deionized water, add 0.095 g of sodium tellurite, stir to form a homogeneous solution, then add 1.65 mL of hydrazine hydrate and 3.35 mL of ammonia water to it, continue stirring for 30 min, and then put the mixed solution into an oven at 200 °C for hydrothermal treatment for 3.5 h. After the hydrothermal treatment is completed and it cools down, separate the tellurium nanowire solid with acetone, and dissolve it in 50 mL of deionized water to form a tellurium nanowire aqueous solution;

[0041] 2) Synthesis of intermediate product: Weigh 2 mmol of zinc nitrate and 0.5 g of glucosamine, dissolve them in 25 mL of the above-prepared tellurium nanowire solution, stir for 1 h, and then put the mixed solution into an oven at 180 °C for hydrothermal treatment for 15 h. After the hydrothermal treatment is completed and it cools down, obtain a black aerogel through freeze-drying;

[0042] 3) Preparation of zinc single-atom loaded porous carbon nanotubes: Heat-treat the black aerogel prepared in step 2) at a programmed heating rate of 3 °C / min -1 in a nitrogen atmosphere to 900 °C, hold at this temperature for 2 h, and then cool to obtain zinc single-atom loaded porous carbon nanotubes.

[0043] Example 4

[0044] A method for preparing zinc single-atom loaded porous carbon nanotubes, comprising the following steps:

[0045] 1) Preparation of tellurium nanowire aqueous solution: Weigh 0.5 g of polyvinylpyrrolidone and dissolve it in 25 mL of deionized water, add 0.095 g of sodium tellurite, stir to form a homogeneous solution, then add 1.65 mL of hydrazine hydrate and 3.35 mL of ammonia water to it, continue stirring for 30 min, and then put the mixed solution into an oven at 180 °C for hydrothermal treatment for 3 h. After the hydrothermal treatment is completed and it cools down, separate the tellurium nanowire solid with acetone, and dissolve it in 50 mL of deionized water to form a tellurium nanowire aqueous solution;

[0046] 2) Synthesis of intermediate product: Weigh 2 mmol of zinc nitrate and 0.5 g of glucosamine, dissolve them in 25 mL of the above-prepared tellurium nanowire solution, stir for 1 h, and then put the mixed solution into an oven at 180 °C for hydrothermal treatment for 15 h. After the hydrothermal treatment is completed and it cools down, obtain a black aerogel through freeze-drying;

[0047] 3) Preparation of zinc single-atom loaded porous carbon nanotubes: Heat-treat the black aerogel prepared in step 2) at a programmed heating rate of 3 °C / min -1Heat to 900 °C for heat treatment, hold at this temperature for 2 h, and then cool to obtain zinc single-atom loaded porous carbon nanotubes.

[0048] Example 5

[0049] A method for preparing zinc single-atom loaded porous carbon nanotubes, comprising the following steps:

[0050] 1) Preparation of tellurium nanowire aqueous solution: Weigh 0.5 g of polyvinylpyrrolidone and dissolve it in 25 mL of deionized water. Add 0.095 g of sodium tellurite, stir to form a homogeneous solution, then add 1.65 mL of hydrazine hydrate and 3.35 mL of ammonia water to it, continue stirring for 30 min, and then put the mixed solution into an oven at 180 °C for hydrothermal treatment for 4 h. After the hydrothermal treatment is completed and it cools down, separate the tellurium nanowire solid with acetone and dissolve it in 50 mL of deionized water to form a tellurium nanowire aqueous solution;

[0051] 2) Synthesis of intermediate product: Weigh 2 mmol of zinc nitrate and 0.5 g of glucosamine, dissolve them in 25 mL of the above-prepared tellurium nanowire solution, stir for 1 h, and then put the mixed solution into an oven at 180 °C for hydrothermal treatment for 15 h. After the hydrothermal treatment is completed and it cools down, obtain a black aerogel through freeze-drying;

[0052] 3) Preparation of zinc single-atom loaded porous carbon nanotubes: Heat the black aerogel prepared in step 2) under a nitrogen atmosphere at a programmed heating rate of 3 °C / min -1 Heat to 900 °C for heat treatment, hold at this temperature for 2 h, and then cool to obtain zinc single-atom loaded porous carbon nanotubes.

[0053] Example 6

[0054] A method for preparing zinc single-atom loaded porous carbon nanotubes, comprising the following steps:

[0055] 1) Preparation of tellurium nanowire aqueous solution: Weigh 0.5 g of polyvinylpyrrolidone and dissolve it in 25 mL of deionized water. Add 0.095 g of sodium tellurite, stir to form a homogeneous solution, then add 1.65 mL of hydrazine hydrate and 3.35 mL of ammonia water to it, continue stirring for 30 min, and then put the mixed solution into an oven at 180 °C for hydrothermal treatment for 3.5 h. After the hydrothermal treatment is completed and it cools down, separate the tellurium nanowire solid with acetone and dissolve it in 50 mL of deionized water to form a tellurium nanowire aqueous solution;

[0056] 2) Synthesis of intermediate product: Weigh 1 mmol of zinc nitrate and 0.5 g of glucosamine, dissolve them in 25 mL of the above-prepared tellurium nanowire solution, stir for 1 h, and then put the mixed solution into an oven at 180 °C for hydrothermal treatment for 15 h. After the hydrothermal treatment is completed and it cools down, obtain a black aerogel through freeze-drying;

[0057] 3) Preparation of zinc single-atom loaded porous carbon nanotubes: The black aerogel obtained in step 2) is heated at a programmed heating rate of 3 °C min -1 to 900 °C under a nitrogen atmosphere for heat treatment, maintained at this temperature for 2 h, and then cooled to obtain zinc single-atom loaded porous carbon nanotubes.

[0058] Example 7

[0059] A method for preparing zinc single-atom loaded porous carbon nanotubes, comprising the following steps:

[0060] 1) Preparation of tellurium nanowire aqueous solution: Weigh 0.5 g of polyvinylpyrrolidone and dissolve it in 25 mL of deionized water, add 0.095 g of sodium tellurite, stir to form a homogeneous solution, then add 1.65 mL of hydrazine hydrate and 3.35 mL of ammonia water thereto, continue stirring for 30 min, and then place the mixed solution in an oven at 180 °C for hydrothermal treatment for 3.5 h. After the hydrothermal treatment is completed and it is cooled, the tellurium nanowire solid is separated by acetone and dissolved in 50 mL of deionized water to form a tellurium nanowire aqueous solution;

[0061] 2) Synthesis of intermediate product: Weigh 4 mmol of zinc nitrate and 0.5 g of glucosamine, dissolve them in 25 mL of the tellurium nanowire solution prepared above, stir for 1 h, and then place the mixed solution in an oven at 180 °C for hydrothermal treatment for 15 h. After the hydrothermal treatment is completed and it is cooled, it is freeze-dried to obtain a black aerogel;

[0062] 3) Preparation of zinc single-atom loaded porous carbon nanotubes: The black aerogel obtained in step 2) is heated at a programmed heating rate of 3 °C min -1 to 900 °C under a nitrogen atmosphere for heat treatment, maintained at this temperature for 2 h, and then cooled to obtain zinc single-atom loaded porous carbon nanotubes.

[0063] Example 8

[0064] A method for preparing zinc single-atom loaded porous carbon nanotubes, comprising the following steps:

[0065] 1) Preparation of tellurium nanowire aqueous solution: Weigh 0.5 g of polyvinylpyrrolidone and dissolve it in 25 mL of deionized water, add 0.095 g of sodium tellurite, stir to form a homogeneous solution, then add 1.65 mL of hydrazine hydrate and 3.35 mL of ammonia water thereto, continue stirring for 30 min, and then place the mixed solution in an oven at 180 °C for hydrothermal treatment for 3.5 h. After the hydrothermal treatment is completed and it is cooled, the tellurium nanowire solid is separated by acetone and dissolved in 50 mL of deionized water to form a tellurium nanowire aqueous solution;

[0066] 2) Synthesis of intermediate product: Weigh 2 mmol of zinc nitrate and 0.5 g of glucosamine, dissolve them in 25 mL of the tellurium nanowire solution prepared above, stir for 1 h, and then place the mixed solution in an oven at 160 °C for hydrothermal treatment for 15 h. After the hydrothermal treatment and cooling, freeze-dry to obtain a black aerogel;

[0067] 3) Preparation of zinc single-atom-loaded porous carbon nanotubes: Heat-treat the black aerogel prepared in step 2) in a nitrogen atmosphere at a programmed heating rate of 3 °C min -1 to 900 °C and hold at this temperature for 2 h, then cool to obtain zinc single-atom-loaded porous carbon nanotubes.

[0068] Example 9

[0069] A method for preparing zinc single-atom-loaded porous carbon nanotubes, comprising the following steps:

[0070] 1) Preparation of tellurium nanowire aqueous solution: Weigh 0.5 g of polyvinylpyrrolidone, dissolve it in 25 mL of deionized water, add 0.095 g of sodium tellurite, stir to form a homogeneous solution, then add 1.65 mL of hydrazine hydrate and 3.35 mL of ammonia water, continue to stir for 30 min, and then place the mixed solution in an oven at 180 °C for hydrothermal treatment for 3.5 h. After the hydrothermal treatment and cooling, separate the tellurium nanowire solid with acetone and dissolve it in 50 mL of deionized water to form a tellurium nanowire aqueous solution;

[0071] 2) Synthesis of intermediate product: Weigh 2 mmol of zinc nitrate and 0.5 g of glucosamine, dissolve them in 25 mL of the tellurium nanowire solution prepared above, stir for 1 h, and then place the mixed solution in an oven at 200 °C for hydrothermal treatment for 15 h. After the hydrothermal treatment and cooling, freeze-dry to obtain a black aerogel;

[0072] 3) Preparation of zinc single-atom-loaded porous carbon nanotubes: Heat-treat the black aerogel prepared in step 2) in a nitrogen atmosphere at a programmed heating rate of 3 °C min -1 to 900 °C and hold at this temperature for 2 h, then cool to obtain zinc single-atom-loaded porous carbon nanotubes.

[0073] Example 10

[0074] A method for preparing zinc single-atom-loaded porous carbon nanotubes, comprising the following steps:

[0075] 1) Preparation of tellurium nanowire aqueous solution: Weigh 0.5 g of polyvinylpyrrolidone and dissolve it in 25 mL of deionized water. Add 0.095 g of sodium tellurite, stir to form a homogeneous solution, then add 1.65 mL of hydrazine hydrate and 3.35 mL of ammonia water to it, continue stirring for 30 min, and then put the mixed solution into an oven at 180 °C for hydrothermal treatment for 3.5 h. After the hydrothermal treatment is completed and it cools down, separate the tellurium nanowire solid with acetone, and dissolve it in 50 mL of deionized water to form a tellurium nanowire aqueous solution;

[0076] 2) Synthesis of intermediate product: Weigh 2 mmol of zinc nitrate and 0.5 g of glucosamine, dissolve them in 25 mL of the tellurium nanowire solution prepared above, stir for 1 h, and then put the mixed solution into an oven at 180 °C for hydrothermal treatment for 12 h. After the hydrothermal treatment is completed and it cools down, obtain a black aerogel through freeze-drying;

[0077] 3) Preparation of zinc single-atom-loaded porous carbon nanotubes: Heat-treat the black aerogel prepared in step 2) at a programmed heating rate of 3 °C / min -1 in a nitrogen atmosphere up to 900 °C, hold at this temperature for 2 h, and then cool down to obtain zinc single-atom-loaded porous carbon nanotubes.

[0078] Example 11

[0079] A method for preparing zinc single-atom-loaded porous carbon nanotubes, comprising the following steps:

[0080] 1) Preparation of tellurium nanowire aqueous solution: Weigh 0.5 g of polyvinylpyrrolidone and dissolve it in 25 mL of deionized water. Add 0.095 g of sodium tellurite, stir to form a homogeneous solution, then add 1.65 mL of hydrazine hydrate and 3.35 mL of ammonia water to it, continue stirring for 30 min, and then put the mixed solution into an oven at 180 °C for hydrothermal treatment for 3.5 h. After the hydrothermal treatment is completed and it cools down, separate the tellurium nanowire solid with acetone, and dissolve it in 50 mL of deionized water to form a tellurium nanowire aqueous solution;

[0081] 2) Synthesis of intermediate product: Weigh 2 mmol of zinc nitrate and 0.5 g of glucosamine, dissolve them in 25 mL of the tellurium nanowire solution prepared above, stir for 1 h, and then put the mixed solution into an oven at 180 °C for hydrothermal treatment for 18 h. After the hydrothermal treatment is completed and it cools down, obtain a black aerogel through freeze-drying;

[0082] 3) Preparation of zinc single-atom-loaded porous carbon nanotubes: Heat-treat the black aerogel prepared in step 2) at a programmed heating rate of 3 °C / min -1 in a nitrogen atmosphere up to 900 °C, hold at this temperature for 2 h, and then cool down to obtain zinc single-atom-loaded porous carbon nanotubes.

[0083] Example 12

[0084] Preparation method of zinc single-atom loaded porous carbon nanotubes, comprising the following steps:

[0085] 1) Preparation of tellurium nanowire aqueous solution: Weigh 0.5 g of polyvinylpyrrolidone and dissolve it in 25 mL of deionized water, add 0.095 g of sodium tellurite, stir to form a homogeneous solution, then add 1.65 mL of hydrazine hydrate and 3.35 mL of ammonia water thereto, continue stirring for 30 min, and then place the mixed solution in an oven at 180 °C for hydrothermal treatment for 3.5 h. After the hydrothermal treatment is completed and it is cooled, the tellurium nanowire solid is separated by acetone and dissolved in 50 mL of deionized water to form a tellurium nanowire aqueous solution;

[0086] 2) Synthesis of intermediate product: Weigh 2 mmol of zinc nitrate and 0.5 g of glucosamine, dissolve them in 25 mL of the above-prepared tellurium nanowire solution, stir for 1 h, and then place the mixed solution in an oven at 180 °C for hydrothermal treatment for 15 h. After the hydrothermal treatment is completed and it is cooled, freeze-dry to obtain a black aerogel;

[0087] 3) Preparation of zinc single-atom loaded porous carbon nanotubes: Heat-treat the black aerogel prepared in step 2) in a nitrogen atmosphere at a programmed heating rate of 1 °C / min -1 to 900 °C, hold at this temperature for 2 h, and then cool to obtain zinc single-atom loaded porous carbon nanotubes.

[0088] Example 13

[0089] Preparation method of zinc single-atom loaded porous carbon nanotubes, comprising the following steps:

[0090] 1) Preparation of tellurium nanowire aqueous solution: Weigh 0.5 g of polyvinylpyrrolidone and dissolve it in 25 mL of deionized water, add 0.095 g of sodium tellurite, stir to form a homogeneous solution, then add 1.65 mL of hydrazine hydrate and 3.35 mL of ammonia water thereto, continue stirring for 30 min, and then place the mixed solution in an oven at 180 °C for hydrothermal treatment for 3.5 h. After the hydrothermal treatment is completed and it is cooled, the tellurium nanowire solid is separated by acetone and dissolved in 50 mL of deionized water to form a tellurium nanowire aqueous solution;

[0091] 2) Synthesis of intermediate product: Weigh 2 mmol of zinc nitrate and 0.5 g of glucosamine, dissolve them in 25 mL of the above-prepared tellurium nanowire solution, stir for 1 h, and then place the mixed solution in an oven at 180 °C for hydrothermal treatment for 15 h. After the hydrothermal treatment is completed and it is cooled, freeze-dry to obtain a black aerogel;

[0092] 3) Preparation of zinc single-atom loaded porous carbon nanotubes: Heat-treat the black aerogel prepared in step 2) in a nitrogen atmosphere at a programmed heating rate of 5 °C / min -1 to 900 °C, hold at this temperature for 2 h, and then cool to obtain zinc single-atom loaded porous carbon nanotubes.

[0093] Example 14

[0094] A method for preparing zinc single-atom loaded porous carbon nanotubes, comprising the following steps:

[0095] 1) Preparation of tellurium nanowire aqueous solution: Weigh 0.5 g of polyvinylpyrrolidone and dissolve it in 25 mL of deionized water, add 0.095 g of sodium tellurite, stir to form a homogeneous solution, then add 1.65 mL of hydrazine hydrate and 3.35 mL of ammonia water thereto, continue stirring for 30 min, and then place the mixed solution in an oven at 180 °C for hydrothermal treatment for 3.5 h. After the hydrothermal treatment is completed and it is cooled, the tellurium nanowire solid is separated by acetone and dissolved in 50 mL of deionized water to form a tellurium nanowire aqueous solution;

[0096] 2) Synthesis of intermediate product: Weigh 2 mmol of zinc nitrate and 0.5 g of glucosamine, dissolve them in 25 mL of the above-prepared tellurium nanowire solution, stir for 1 h, and then place the mixed solution in an oven at 180 °C for hydrothermal treatment for 15 h. After the hydrothermal treatment is completed and it is cooled, it is freeze-dried to obtain a black aerogel;

[0097] 3) Preparation of zinc single-atom loaded porous carbon nanotubes: The black aerogel prepared in step 2) is heated to 800 °C at a programmed heating rate of 3 °C / min in a nitrogen atmosphere, held at this temperature for 2 h, and then cooled to obtain zinc single-atom loaded porous carbon nanotubes. -1

[0098] Example 15

[0099] A method for preparing zinc single-atom loaded porous carbon nanotubes, comprising the following steps:

[0100] 1) Preparation of tellurium nanowire aqueous solution: Weigh 0.5 g of polyvinylpyrrolidone and dissolve it in 25 mL of deionized water, add 0.095 g of sodium tellurite, stir to form a homogeneous solution, then add 1.65 mL of hydrazine hydrate and 3.35 mL of ammonia water thereto, continue stirring for 30 min, and then place the mixed solution in an oven at 180 °C for hydrothermal treatment for 3.5 h. After the hydrothermal treatment is completed and it is cooled, the tellurium nanowire solid is separated by acetone and dissolved in 50 mL of deionized water to form a tellurium nanowire aqueous solution;

[0101] 2) Synthesis of intermediate product: Weigh 2 mmol of zinc nitrate and 0.5 g of glucosamine, dissolve them in 25 mL of the above-prepared tellurium nanowire solution, stir for 1 h, and then place the mixed solution in an oven at 180 °C for hydrothermal treatment for 15 h. After the hydrothermal treatment is completed and it is cooled, it is freeze-dried to obtain a black aerogel;

[0102] 3) Preparation of zinc single-atom loaded porous carbon nanotubes: The black aerogel prepared in step 2) is heated to 800 °C at a programmed heating rate of 3 °C / min in a nitrogen atmosphere, held at this temperature for 2 h, and then cooled. -1 ​Heat it to 1000 °C for heat treatment, hold at this temperature for 2 h, and then cool it to obtain zinc single-atom loaded porous carbon nanotubes.

[0103] Example 16

[0104] A method for preparing zinc single-atom loaded porous carbon nanotubes, comprising the following steps:

[0105] 1) Preparation of tellurium nanowire aqueous solution: Weigh 0.5 g of polyvinylpyrrolidone and dissolve it in 25 mL of deionized water, add 0.095 g of sodium tellurite, stir to form a homogeneous solution, then add 1.65 mL of hydrazine hydrate and 3.35 mL of ammonia water thereto, continue stirring for 30 min, and then put the mixed solution into an oven at 180 °C for hydrothermal treatment for 3.5 h. After the hydrothermal treatment is completed and it is cooled, separate the tellurium nanowire solid with acetone, and dissolve it in 50 mL of deionized water to form a tellurium nanowire aqueous solution;

[0106] 2) Synthesis of intermediate product: Weigh 2 mmol of zinc nitrate and 0.5 g of glucosamine, dissolve them in 25 mL of the above-prepared tellurium nanowire solution, stir for 1 h, and then put the mixed solution into an oven at 180 °C for hydrothermal treatment for 15 h. After the hydrothermal treatment is completed and it is cooled, obtain a black aerogel through freeze-drying;

[0107] 3) Preparation of zinc single-atom loaded porous carbon nanotubes: Heat the black aerogel prepared in step 2) at a programmed heating rate of 3 °C / min -1 in a nitrogen atmosphere to 900 °C for heat treatment, hold at this temperature for 1 h, and then cool it to obtain zinc single-atom loaded porous carbon nanotubes.

[0108] Example 17

[0109] A method for preparing zinc single-atom loaded porous carbon nanotubes, comprising the following steps:

[0110] 1) Preparation of tellurium nanowire aqueous solution: Weigh 0.5 g of polyvinylpyrrolidone and dissolve it in 25 mL of deionized water, add 0.095 g of sodium tellurite, stir to form a homogeneous solution, then add 1.65 mL of hydrazine hydrate and 3.35 mL of ammonia water thereto, continue stirring for 30 min, and then put the mixed solution into an oven at 180 °C for hydrothermal treatment for 3.5 h. After the hydrothermal treatment is completed and it is cooled, separate the tellurium nanowire solid with acetone, and dissolve it in 50 mL of deionized water to form a tellurium nanowire aqueous solution;

[0111] 2) Synthesis of intermediate product: Weigh 2 mmol of zinc nitrate and 0.5 g of glucosamine, dissolve them in 25 mL of the above-prepared tellurium nanowire solution, stir for 1 h, and then put the mixed solution into an oven at 180 °C for hydrothermal treatment for 15 h. After the hydrothermal treatment is completed and it is cooled, obtain a black aerogel through freeze-drying;

[0112] 3) Preparation of zinc single-atom loaded porous carbon nanotubes: The black aerogel obtained in step 2) was heated at a programmed heating rate of 3 °C min -1 to 900 °C under a nitrogen atmosphere for heat treatment, maintained at this temperature for 3 h, and then cooled to obtain zinc single-atom loaded porous carbon nanotubes.

[0113] The zinc single-atom loaded porous carbon nanotubes prepared in the above examples were characterized by means such as TEM, SEM, AC-STEM, and XRD. From the transmission electron microscopy images (TEM, Figure 1 ), its uniform one-dimensional tubular structure can be clearly observed. The scanning electron microscopy images (SEM, Figure 2 ) also show that the prepared zinc single-atom loaded porous carbon nanotubes have a uniform morphology, presenting an interlaced network structure. Further analysis by aberration-corrected scanning transmission electron microscopy images (AC-STEM, Figure 3 ) reveals that Zn is uniformly dispersed at the atomic level on the surface of the obtained product, and the carbon nanotubes also have abundant pores on the surface. From Figure 4 , no metal peak of Zn appears in the XRD pattern, further proving the successful preparation of zinc single-atom loaded porous carbon nanotubes. Figure 5 and Figure 6 are the comparisons of the activity and stability of the two catalysts respectively. It can be seen from Figure 5 that compared with the commercial Pt / C catalyst (purchased from Johnson Matthey, with a Pt mass percentage of 20%), the zinc single-atom loaded porous carbon nanotubes (Zn Sas@CNTs) have better oxygen reduction electrocatalytic activity. After 43200 s of chronoamperometry test ( Figure 6 ), the oxygen reduction activity loss of the zinc single-atom loaded porous carbon nanotubes is smaller, while the oxygen reduction activity of the commercial Pt / C catalyst shows a significant decline, which is mainly attributed to the atomic-level dispersion of the prepared catalyst, which can effectively avoid the dissolution and aggregation of active sites. Applying the zinc single-atom loaded porous carbon nanotube material of the present invention as an air cathode catalyst in a zinc-air battery can stably cycle charge and discharge more than 400 times (>113 h, Figure 7 ), proving that this material has certain potential for practical applications.

Claims

1. A preparation method of zinc single-atom loaded porous carbon nanotubes, characterized in that, it includes the following steps: (1) Using polyvinylpyrrolidone as a surfactant and sodium tellurite in a mixed solution of ammonia water and hydrazine hydrate to generate tellurium nanowires by a one-step hydrothermal method. After separating the tellurium nanowires, they are dissolved in water to obtain an aqueous solution of tellurium nanowires; (2) Adding carbon source glucosamine and metal source zinc nitrate to the above-mentioned aqueous solution of tellurium nanowires, stirring evenly, and then carrying out a hydrothermal reaction. The obtained black complex is freeze-dried to obtain a black aerogel; (3) The black aerogel is subjected to high-temperature calcination treatment and cooled to room temperature to obtain zinc single-atom loaded porous carbon nanotubes.

2. The preparation method of zinc single-atom loaded porous carbon nanotubes according to claim 1, characterized in that, in step (1), the hydrothermal temperature of the hydrothermal method is 160°C to 200°C, and the hydrothermal time is 3 to 4 h.

3. The preparation method of zinc single-atom loaded porous carbon nanotubes according to claim 1, characterized in that, in step (2), the input molar amount of zinc nitrate is 1 to 4 mmol.

4. The preparation method of zinc single-atom loaded porous carbon nanotubes according to claim 1, characterized in that, in step (2), the reaction temperature of the hydrothermal reaction is 160°C to 200°C, and the reaction time is 12 to 18 h.

5. The preparation method of zinc single-atom loaded porous carbon nanotubes according to claim 1, characterized in that, in step (3), the high-temperature calcination treatment is carried out in an inert atmosphere, and the inert atmosphere is one or more mixtures of nitrogen, helium or argon.

6. The preparation method of zinc single-atom loaded porous carbon nanotubes according to claim 1, characterized in that, The temperature of the high-temperature calcination treatment described in step (3) is 800°C to 1000°C, and the heating rate is 0.5 to 10 °C·min -1 , and the heat treatment time is 1 to 3 h.

7. A zinc single-atom loaded porous carbon nanotube prepared by the preparation method according to any one of claims 1-6.

8. An application of the zinc single-atom loaded porous carbon nanotube according to claim 7 as a cathode oxygen reduction catalyst in a fuel cell in an alkaline electrolyte.

9. An application of the zinc single-atom loaded porous carbon nanotube according to claim 7 as an air cathode catalyst in a zinc-air battery.

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