A pvdf-based self-supported monatomic electrocatalyst and a preparation method thereof

Abstract

The application discloses a preparation method of a PVDF-based self-supporting monatomic electrocatalyst, uses polyvinylidene fluoride (PVDF) as a carbon precursor material, obtains a porous fiber with a large specific surface area through an electrostatic spinning technology, uses a crosslinking agent to make the PVDF obtain a reticular skeleton, uses carbon vacancy bonding metal atoms left by removal of-CF free radicals in a pyrolysis process to obtain a monatomic electrocatalyst, and the monatomic electrocatalyst of different metals can be prepared by changing metal salts, and the monatomic metal catalyst doped with N, P, S and other heteroatoms can be obtained by doping different reagents. The monatomic electrocatalyst prepared by the application has a self-supporting performance and can be directly used as an electrode material, effectively expands the use area, can be used in multiple fields such as hydrogen production, CO2 reduction, artificial nitrogen fixation, wastewater treatment, supercapacitors, battery materials and the like, has high stability, and has a simple preparation method.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrochemistry, and relates to a self-supporting single-atom metal catalyst prepared by using polyvinylidene fluoride (PVDF) as a carbon precursor material, in particular to a preparation method of a PVDF-based self-supporting single-atom electrocatalyst. BACKGROUND

[0002] Electrocatalytic hydrogen production and electrocatalytic carbon dioxide reduction are effective means to obtain clean energy and achieve carbon neutrality. Among numerous catalysts, single-atom catalysts have attracted widespread attention due to their 100% atom utilization efficiency. Single-atom catalyst supports include metals, metal compounds, and carbon supports, among which low-dimensional carbon supports have attracted widespread attention due to their large specific surface area, high electrical conductivity, and strong thermal stability. Single-atom catalysts prepared using carbon supports are usually obtained by pyrolysis of organic precursors (such as MOF materials), and the single-atom catalysts are bonded to the carbon skeleton or coated with carbon materials, thereby having good stability. However, the preparation of metal catalyst precursors is usually cumbersome, and the precursor material is prone to structural collapse during pyrolysis, reducing catalyst exposure. At the same time, single atoms have very high surface energy and are prone to fusion into clusters or even form larger particles during the pyrolysis process, thereby losing catalytic activity. In terms of electrode preparation, the electrocatalyst obtained by pyrolysis of a carbon material precursor is usually in powder form and needs to be bonded to a conductive substrate using a binder, which limits the number of available surface catalysts and reduces the stability of the catalyst after long-term use. SUMMARY

[0003] To solve the above problems, the application provides a PVDF-based self-supporting single-atom electrocatalyst and a preparation method thereof, to overcome the poor stability of the powder electrocatalyst, fix the single-atom metal catalyst on a high-specific-surface-area carbon fiber membrane, improve the stability of the carbon bonding material, and obtain a highly efficient and stable electrocatalyst.

[0004] The application is implemented by the following technical solutions:

[0005] A preparation method of a PVDF-based self-supporting single-atom electrocatalyst, comprising the following steps:

[0006] (1) Preparation of a PVDF fiber membrane: dissolve PVDF in a mixed solvent of N, N-dimethylformamide and acetone, add a metal salt and stir until completely dissolved as a spinning solution, use an electrospinning technology to prepare a PVDF fiber membrane, and dry it; the metal is a transition metal or a p-block metal;

[0007] (2) Skeleton crosslinking: prepare NaOH methanol solution, add appropriate amount of p-xylylenediamine to dissolve, then add the PVDF fiber membrane prepared in step (1), so that crosslinking reaction occurs, after the reaction is completed, the PVDF fiber membrane is taken out, washed and dried;

[0008] (3) Carbonization: after crosslinking, the PVDF fiber membrane is placed in a tube furnace, heated to 900 ℃ at a rate of 5 ℃ / min under argon atmosphere, and maintained at the temperature for two hours to obtain a PVDF-based self-supported metal-C monatomic electrocatalyst.

[0009] Further, the carbonization in step (3) further includes doped carbonization, specifically N-doped carbonization, P-doped carbonization or S-doped carbonization.

[0010] Further, the N-doped carbonization is that the PVDF fiber membrane after crosslinking is heated to 900 ℃ at a rate of 5 ℃ / min under an argon and ammonia atmosphere with a volume ratio of 1:1, and maintained at the temperature for two hours to obtain a PVDF-based self-supported metal-N-C monatomic electrocatalyst; the P-doped carbonization is that a porcelain boat with sodium hypophosphite and the crosslinked PVDF fiber membrane at both ends is placed in a tube furnace, heated to 320 ℃ at a rate of 2 ℃ / min under argon protection, and maintained at the temperature for two hours, then heated to 900 ℃ at a rate of 5 ℃ / min, and maintained at the temperature for two hours to obtain a PVDF-based self-supported metal-P-C monatomic electrocatalyst; and the S-doped carbonization step is that a porcelain boat with sublimed sulfur and the crosslinked PVDF fiber membrane at both ends is placed in a tube furnace, heated to 320 ℃ at a rate of 2 ℃ / min under argon protection, and maintained at the temperature for two hours, then heated to 900 ℃ at a rate of 5 ℃ / min, and maintained at the temperature for two hours to obtain a PVDF-based self-supported metal-S-C monatomic electrocatalyst.

[0011] Further, the sodium hypophosphite and the sublimed sulfur are close to one end of the gas inlet of the tube furnace.

[0012] Further, when the volume of the PVDF fiber membrane is 10 cm×10 cm, the amount of sodium hypophosphite and sublimed sulfur is 0.5-2 g.

[0013] Further, the transition metal is Fe, Ni, Co, Cu, Pt, Au, Ag, Ru, Zn, Mn or Pd, and the p-block metal mainly includes Sn, Pb and Bi.

[0014] Further, in step (1), the volume ratio of N,N-dimethylformamide and acetone is 2:3, the concentration of the PVDF solution is 10 wt%, and the amount of metal salt added is 0.5-2% of the mass of PVDF.

[0015] Further, the electrospinning condition in step (1) is: the applied voltage is 1.5 KV cm −1 , the distance between the needle and the drum is 15 cm, and the continuous collection of the spinning is 10 hours; and the drying temperature of the PVDF fiber membrane is 60 DEG C.

[0016] Further, the mass concentration of the NaOH methanol solution in step (2) is 6%, the mass concentration of the p-phenylenediamine is 20%, the crosslinking reaction time is 48 h, and the washing method is sequentially immersing in 1 M nitric acid, deionized water and methanol for two hours each, and drying at 60 DEG C.

[0017] In the application, the PVDF-based self-supporting monatomic electrocatalyst is prepared by the method.

[0018] In the application, polyvinylidene fluoride (PVDF) is used as a carbon precursor material to prepare a self-supporting monatomic metal electrocatalyst, and this material has not been reported to be used in the synthesis of electrocatalysts. A porous fiber with a large specific surface area is obtained by electrospinning technology, and a network skeleton is obtained by using a crosslinking agent, so that the basic structure is not collapsed during pyrolysis. In the application, metal atoms are bonded to carbon vacancies left by the removal of -CF free radicals during pyrolysis, and a monatomic catalyst is obtained. The micropores obtained by the removal of -CF free radicals enhance the adsorption of gas and increase the exposure of the catalyst. The carbon fiber-loaded monatomic catalyst with a porous structure prepared in the application has metal atoms bonded to the carbon structure, and has good stability and dispersity. At the same time, the catalyst has self-supporting performance and can be directly used as an electrode material, effectively expanding the use area.

[0019] In the application, different metal monatomic electrocatalysts can be prepared by changing metal salts, and N, P, S and other heteroatom-doped monatomic metal electrocatalysts can be obtained by doping different reagents. The fiber maintains the original morphology after carbonization, and a high specific surface area carbonized fiber membrane can be obtained and directly used as a self-supporting electrode, avoiding the defects of easy falling of powder catalyst, decrease of conductivity due to adhesion and decrease of available active components. The PVDF-based self-supporting monatomic electrocatalyst prepared in the application can be used in the fields of hydrogen production, CO2 reduction, artificial nitrogen fixation, wastewater treatment, supercapacitors, battery materials and the like, due to the different transition metals and doped heteroatoms. Since the utilization efficiency of the monatomic catalyst is 100% and the stability of the carbon combined material is high, the application is a high-efficiency and stable electrocatalyst, and the preparation method is simple.

[0020] Advantages

[0021] The preparation method provided by the application is a method for preparing a general metal monatomic or heteroatom-doped metal monatomic electrocatalyst using PVDF as a carrier. The basic principle is to use a cross-linked structure as a skeleton, use pyrolysis process CF removal to manufacture vacancies for heteroatom doping and metal atom anchoring, obtain a self-supporting metal monatomic catalyst, and use the transition metal and different doped heteroatoms for hydrogen production, CO2 reduction, artificial nitrogen fixation, wastewater treatment, supercapacitors, battery materials and other fields. Due to the 100% utilization efficiency of the monatomic catalyst and the stability of the carbon combined material, it is a high-efficiency and stable electrocatalyst, and the preparation method is simple. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 Morphology of PVDF-based self-supporting Fe-C monatomic electrocatalyst, Figure 1 (a) is a laboratory demonstration result, Figure 1 (b) shows that the prepared carbonized film can be directly clamped as an electrode;

[0023] Figure 2 PVDF-based self-supporting Fe-C monatomic electrocatalyst PVDF carbonized fiber SEM (a, b) and TEM (c) figure;

[0024] Figure 3 Single atom structure spherical aberration electron microscope figure (a) PVDF-based self-supporting Fe-C monatomic electrocatalyst (b) PVDF-based self-supporting Fe-N-C monatomic electrocatalyst;

[0025] Figure 4 Synchronous radiation measurement result of PVDF-based self-supporting Fe-C and Fe-N-C monatomic electrocatalyst;

[0026] Figure 5 PVDF-based self-supporting Fe-C and Fe-N-C monatomic electrocatalyst hydrogen production and CO2 reduction to CO efficiency;

[0027] Figure 6 PVDF-based self-supporting Ni-N-C monatomic electrocatalyst carbonized fiber SEM figure (a, b), polarization curve (c) and product catalytic reduction selectivity (d);

[0028] Figure 7 PVDF-based self-supporting Ag-C monatomic electrocatalyst carbonized fiber SEM figure (a, b) and product catalytic reduction selectivity (c. Product under different overvoltage; d. Reduction selectivity of catalysts with different Ag doping amounts at -0.56V). DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. The described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] The catalytic performance testing method for PVDF-based self-supporting single-atom electrocatalysts in the examples is as follows:

[0031] Performance testing was conducted using an electrochemical workstation, employing an H-type electrolyzer for hydrogen production and CO2 reduction. A conventional three-electrode system was used for measurements. A 1 cm × 1 cm piece of the carbon fiber membrane catalyst was cut as the working electrode, a saturated calomel electrode (SCE) as the reference electrode, and a platinum sheet electrode as the counter electrode. A 0.5 M NaHCO3 solution was used as the electrolyte. During testing, the selected voltage range was 0 to −1.1 V, the scan rate was 5 mV / s, and the voltage with the highest Faraday efficiency was determined through preliminary experiments. Electrolysis was performed for 1 hour, and product analysis was conducted using gas chromatography.

[0032] Example 1

[0033] (1) Mix N,N-dimethylformamide and acetone (volume ratio 2:3) to obtain a mixed solvent;

[0034] (2) 10 g of PVDF powder was placed in 90 g of the above solvent, and 0.2 g of FeCl3•6H2O was added. The mixture was magnetically stirred for 6 hours to obtain a transparent spinning solution.

[0035] (3) Take 5 mL of the above spinning solution into a syringe, place the syringe on an electrospinning machine for spinning, use a roller covered with aluminum foil as a collecting device, and apply a voltage of 1.5 KV cm. −1 The distance from the needle to the roller is 15 cm. The spinning is continuously collected for 10 hours to obtain PVDF fiber membrane, which is then dried at 60 ℃ for later use.

[0036] (4) Prepare 20 mL of NaOH methanol solution with a mass concentration of 6%, add 4 g of p-phenylenediamine, stir to dissolve, put a PVDF fiber membrane with an area of ​​10 cm × 10 cm into the solution, and place the mixture on a shaker for cross-linking reaction for 48 hours. After the reaction is completed, take out the PVDF fiber membrane, soak it in 1 M nitric acid, deionized water and methanol for two hours each, and dry it at 60 °C for later use.

[0037] (5) The cross-linked PVDF fiber membrane obtained in step (4) is placed in a tube furnace and heated to 900 °C at a rate of 5 °C / min under an argon atmosphere. The temperature is maintained for two hours to obtain a PVDF-based self-supporting Fe-C single-atom electrocatalyst.

[0038] Example 2

[0039] (1) Mix N,N-dimethylformamide and acetone (volume ratio 2:3) to obtain a mixed solvent;

[0040] (2) 10 g of PVDF powder was placed in 90 g of the above solvent, and 0.2 g of FeCl3•6H2O was added. The mixture was magnetically stirred for 6 hours to obtain a transparent spinning solution.

[0041] (3) Take 5 mL of the above spinning solution into a syringe, place the syringe on an electrospinning machine for spinning, use a roller covered with aluminum foil as a collecting device, and apply a voltage of 1.5 KV cm. −1 The distance from the needle to the roller is 15 cm. The spinning is continuously collected for 10 hours to obtain PVDF fiber membrane, which is then dried at 60 ℃ for later use.

[0042] (4) Prepare 20 mL of NaOH methanol solution with a mass concentration of 6%, add 4 g of p-phenylenediamine, stir to dissolve, put a PVDF fiber membrane with an area of ​​10 cm × 10 cm into the solution, and place the mixture on a shaker for cross-linking reaction for 48 hours. After the reaction is completed, take out the PVDF fiber membrane, soak it in 1 M nitric acid, deionized water and methanol for two hours each, and dry it at 60 °C for later use.

[0043] (5) The cross-linked PVDF fiber membrane obtained in step (4) is placed in a tube furnace and heated to 900 °C at a rate of 5 °C / min under an atmosphere of argon and ammonia in a ratio of 1:1. The temperature is maintained for two hours to obtain a PVDF-based self-supporting Fe-NC single-atom electrocatalyst.

[0044] Figure 1 The image shows the morphology of a PVDF-based self-supporting Fe-C single-atom electrocatalyst. Figure 1 (a) is a laboratory demonstration result; the prepared carbide film can be scaled up depending on the diameter of the tube furnace. Figure 1 (b) The prepared carbonized film can be directly clamped and used as an electrode without being pasted onto conductors such as carbon cloth, and can be used as a self-supporting electrode.

[0045] Figure 2 SEM (a, b) and TEM (c) images of PVDF-based self-supporting Fe-C single-atom electrocatalyst carbonized fibers; Figure 2 (a) shows that the carbonized fiber has a complete morphology and a network structure with micron-sized pores between fibers, which facilitates gas diffusion; Figure 2 (b) Shows that some tissues overflowed after pyrolysis, leaving pores on the fiber surface; Figure 2 (c) The fiber has a loose and porous internal structure, which facilitates gas adsorption;

[0046] Figure 3 For single-atom structure spherical aberration electron microscopy, (a) PVDF-based self-supported Fe-CF single-atom electrocatalyst (b) PVDF-based self-supported Fe-N-C single-atom electrocatalyst; from Figure 3 It can be seen that, whether it is a PVDF-based self-supported Fe-C-based electrocatalyst or a PVDF-based self-supported Fe-N-C single-atom electrocatalyst, Fe (bright spots in the figure) is atomically dispersed in the system;

[0047] Figure 4 For PVDF-based self-supported Fe-C and Fe-N-C single-atom electrocatalyst, the results of synchrotron radiation measurement are as follows: Figure 4 It can be seen that, whether it is a PVDF-based self-supported Fe-C-based electrocatalyst or a PVDF-based self-supported Fe-N-C single-atom electrocatalyst, there is no Fe-Fe characteristic peak, indicating that Fe is not aggregated and is in a single-atom state.

[0048] Figure 5 For PVDF-based self-supported Fe-C and Fe-N-C single-atom electrocatalyst, the efficiency of hydrogen production and CO2 reduction to CO is as follows: Figure 5 It can be seen that the PVDF-based self-supported Fe-C single-atom electrocatalyst mainly produces H2; while the PVDF-based Fe-N-C single-atom catalyst almost produces CO, showing high reduction selectivity; through testing, the PVDF-based self-supported Fe-N-C single-atom electrocatalyst has a CO yield of 4076 ppm· mg -1 ·h -1 under the condition of 2% FeCl3·6H2O addition.

[0049] Example 3

[0050] (1) Mix N, N-dimethylformamide and acetone (volume ratio 2:3) to obtain a mixed solvent;

[0051] (2) 10 g of PVDF powder is placed in 90 g of the above-mentioned solvent, 0.1 g of Ni(NO3)2 is added, and magnetic stirring is carried out for 6 hours to obtain a transparent spinning solution;

[0052] (3) Take 5 mL of the above-mentioned spinning solution in a needle tube, place the needle tube on the electrospinning machine for spinning operation, use an aluminum foil-coated roller as a collection device, apply a voltage of 1.5 KV cm −1 , the distance between the needle head and the roller is 15 cm, and the spinning is continuously collected for 10 hours to obtain a PVDF fiber membrane, which is dried at 60 ℃ for standby use;

[0053] (4) Prepare 20 mL of 6% NaOH methanol solution, add 4 g of p-xylylamine, stir to dissolve, place a PVDF fiber membrane with an area of 10 cm x 10 cm in the solution, and place the mixed system in a shaking bed for crosslinking reaction for 48 hours. After the reaction is completed, take out the PVDF fiber membrane, and sequentially soak in 1 M nitric acid, deionized water, and methanol for two hours each, and dry at 60°C for standby use;

[0054] (5) Place the crosslinked PVDF fiber membrane obtained in step (4) in a tube furnace, heat to 900°C at a rate of 5°C / min under an atmosphere of argon and ammonia at a ratio of 1:1, and maintain the temperature for two hours to obtain a PVDF-based self-supported Ni-N-C single-atom electrocatalyst.

[0055] In step (2), the amount of Ni(NO3)2 added is 0 g, 0.05 g, 0.1 g, and 0.2 g, respectively, to study the performance of the PVDF-based self-supported Ni-N-C single-atom electrocatalyst with different amounts of Ni(NO3)2 added;

[0056] Figure 6 (a, b) are SEM images of the PVDF-based self-supported Ni-N-C single-atom electrocatalyst PVDF carbonized fiber, 6(c) is the polarization curve of the PVDF-based self-supported Ni-N-C single-atom electrocatalyst, and 6(d) is the reduction selectivity of the PVDF-based self-supported Ni-N-C single-atom electrocatalyst. As known from Figure 6 (c, d), the Ni-N-C with a 1.0% Ni doping amount has the highest catalytic activity and the best CO conversion selectivity at -0.61 V; it is tested that the PVDF-based self-supported Ni-N-C single-atom electrocatalyst has a CO yield of 6832 ppm· mg -1 ·h -1 .

[0057] Example 4

[0058] (1) Mix N, N-dimethylformamide and acetone (volume ratio 2:3) to obtain a mixed solvent;

[0059] (2) Put 10 g of PVDF powder into 90 g of the above solvent, add AgNO3, and magnetically stir for 6 hours to obtain a transparent spinning solution;

[0060] (3) Take 5 mL of the above spinning solution in a needle tube, place the needle tube on an electrospinning machine for spinning operation, use an aluminum foil-coated roller as a collection device, apply a voltage of 1.5 KV cm −1 , the distance between the needle and the roller is 15 cm, and the spinning is continuously collected for 10 hours to obtain a PVDF fiber membrane, which is dried at 60°C for standby use;

[0061] (4) 20 mL of 6% NaOH methanol solution was prepared, 4 g of p-xylylenediamine was added and stirred to dissolve, a PVDF fiber membrane with an area of 10 cm x 10 cm was placed in the solution, and the mixed system was placed on a shaker for crosslinking reaction for 48 hours. After the reaction was completed, the PVDF fiber membrane was taken out and sequentially soaked in 1 M nitric acid, deionized water and methanol for two hours each, and dried at 60°C for standby;

[0062] (5) The crosslinked PVDF fiber membrane obtained in step (4) was placed in a tube furnace, heated to 900°C at a rate of 5°C / min under an argon atmosphere, and maintained at this temperature for two hours to obtain a PVDF-based self-supported Ag-C monatomic electrocatalyst.

[0063] In step (2), the amount of AgNO3 added was 0 g, 0.05 g, 0.1 g, 0.2 g and 0.5 g, respectively, to study the performance of the PVDF-based self-supported Ag-C monatomic electrocatalyst with different amounts of AgNO3 added.

[0064] Figure 7 The SEM images of the carbonized fiber of the PVDF-based self-supported Ag-C monatomic electrocatalyst (a, b) and the product catalytic reduction selectivity (c. Products at different overvoltages; d. Reduction selectivity of catalysts with different Ag addition amounts at -0.56 V) are known from Figure 7 The prepared Ag-CF catalyst has good CH4 generation selectivity under appropriate voltage and Ag addition amount.

[0065] Example 5

[0066] Steps (1)~(4) are the same as in Example 1.

[0067] (5) 0.2 g of sodium hypophosphite monohydrate was weighed and placed at one end of the porcelain boat, and the crosslinked PVDF fiber membrane covered the other end of the porcelain boat. The porcelain boat was placed in a tube furnace, with sodium hypophosphite near the gas inlet end, and heated to 400°C at a rate of 2°C / min under argon protection and maintained for two hours, then heated to 900°C at a rate of 5°C / min, and maintained at this temperature for two hours to obtain a PVDF-based self-supported Fe-P-C monatomic electrocatalyst. It is applied to the fields of hydrogen production, carbon dioxide reduction, artificial nitrogen fixation, wastewater treatment and battery materials, etc.

[0068] Example 6

[0069] Steps (1)~(4) are the same as in Example 1.

[0070] (5) Take 0.5 g of sublimed sulfur and place it at one end of a porcelain boat. After cross-linking, cover the other end of the porcelain boat with a PVDF fiber membrane. Place the porcelain boat in a tube furnace, with the sublimed sulfur near the gas inlet end. Under argon protection, heat to 320°C at a rate of 2°C / min and maintain for two hours. Then heat to 900°C at a rate of 5°C / min and maintain the temperature for two hours. Obtain a PVDF-based self-supported Fe-S-CF monatomic electrocatalyst, which can be applied in the production of hydrogen, carbon dioxide reduction, artificial nitrogen fixation, wastewater treatment, and battery materials, etc.

Claims

1. A method of preparing a PVDF-based self-supported monatomic electrocatalyst, characterized in that, The method comprises the following steps: (1) Preparation of the PVDF fiber membrane: dissolve PVDF in a mixed solvent of N, N-dimethylformamide and acetone, add metal salt and stir until completely dissolved as a spinning solution, use electrospinning technology to prepare the PVDF fiber membrane, and dry; the metal is a transition metal or a p-block metal; (2) Skeleton crosslinking: prepare a NaOH methanol solution, add a proper amount of p-xylylenediamine to dissolve, and then add the PVDF fiber membrane prepared in step (1) to make it undergo a crosslinking reaction, and after the reaction is completed, take out the PVDF fiber membrane, wash and dry; (3) Carbonization: place the crosslinked PVDF fiber membrane in a tube furnace, heat to 900 ℃ at a rate of 5 ℃ / min under an argon atmosphere, maintain the temperature for two hours, and obtain a PVDF-based self-supporting metal-C single-atom electrocatalyst.

2. The production method according to claim 1, characterized by, The carbonization in step (3) further comprises doped carbonization, specifically N-doped carbonization, P-doped carbonization or S-doped carbonization.

3. The preparation method according to claim 2, characterized in that, The N-doped carbonization is that the crosslinked PVDF fiber membrane is heated to 900 ℃ at a rate of 5 ℃ / min under an atmosphere of argon and ammonia with a volume ratio of 1:1, and the temperature is maintained for two hours to obtain a PVDF-based self-supporting metal-N-C single-atom electrocatalyst; the P-doped carbonization is that a porcelain boat with sodium hypophosphite and the crosslinked PVDF fiber membrane at both ends is placed in a tube furnace, heated to 320 ℃ at a rate of 2 ℃ / min under an argon atmosphere, and maintained for two hours, and then heated to 900 ℃ at a rate of 5 ℃ / min, and the temperature is maintained for two hours to obtain a PVDF-based self-supporting metal-P-C single-atom electrocatalyst; and the S-doped carbonization step is that a porcelain boat with sublimed sulfur and the crosslinked PVDF fiber membrane at both ends is placed in a tube furnace, heated to 320 ℃ at a rate of 2 ℃ / min under an argon atmosphere, and maintained for two hours, and then heated to 900 ℃ at a rate of 5 ℃ / min, and the temperature is maintained for two hours to obtain a PVDF-based self-supporting metal-S-C single-atom electrocatalyst.

4. The production method according to claim 3, characterized by, The sodium hypophosphite and the sublimed sulfur are close to one end of the gas inlet of the tube furnace.

5. The preparation method according to claim 3, characterized in that, When the area of the PVDF fiber membrane is 10 cm x 10 cm, the amount of sodium hypophosphite and sublimed sulfur is 0.5-2 g.

6. The method of claim 1, wherein, The transition metal is Fe, Ni, Co, Cu, Pt, Au, Ag, Ru, Zn, Mn or Pd, and the p-block metal mainly includes Sn, Pb and Bi.

7. The preparation method according to claim 1, characterized in that, In step (1), the volume ratio of N, N-dimethylformamide and acetone is 2:3, the concentration of the PVDF solution is 10 wt%, and the amount of metal salt added is 0.5-2% of the mass of PVDF.

8. The method of claim 1, wherein, The electrospinning conditions in step (1) are: applied voltage of 1.5 KV·cm -1 , needle-to-drum distance of 15 cm, continuous collection of the spun fibers for 10 hours; and the drying temperature of the PVDF fiber membrane is 60 °C.

9. The method of claim 1, wherein, In step (2), the mass concentration of the NaOH methanol solution is 6%, the mass concentration of p-xylylenediamine is 20%, the crosslinking reaction time is 48 h, the washing method is to sequentially soak in 1 M nitric acid, deionized water and methanol for two hours each, and dry at 60 ℃.

10. A PVDF-based self-supporting single-atom electrocatalyst prepared by the method of any one of claims 1-9.

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