Nitrogen-doped carbon fiber loaded with Ni-Zn bimetallic and application of nitrogen-doped carbon fiber in electrocatalytic reduction of carbon dioxide

Abstract

The invention relates to a Ni-Zn bimetallic loaded nitrogen-doped carbon fiber and an application thereof in electrocatalytic reduction of carbon dioxide, the Ni-Zn bimetallic loaded nitrogen-doped carbon fiber is used as a catalyst, the adsorption performance of a carbon dioxide intermediate product can be optimized through the synergistic effect of Ni and Zn, and the strong binding affinity of Ni and the weak affinity of Zn are balanced; the excessive activation is effectively prevented. Electron transfer in the catalyst promotes rapid electron transfer to carbon dioxide, so that the catalyst shows excellent catalytic performance in the electrochemical reduction reaction of carbon dioxide.

Description

Technical Field

[0001] The present invention belongs to the field of functional materials, and particularly relates to a nitrogen-doped carbon fiber loaded with Ni-Zn bimetal and its application in electrocatalytic reduction of carbon dioxide. Background Art

[0002] To address the global warming issue and promote the storage of renewable energy, electrocatalytic reduction of carbon dioxide (CO2RR) is a promising strategy. It can not only effectively reduce CO2 emissions but also convert CO2 into high-value-added fuels and chemicals, including carbon monoxide (CO), methane, formic acid, methanol, ethanol, ethylene, acetic acid, and propanol. Among these products, CO has particular advantages due to its high economic value, strong selectivity, and easy separation in liquid electrolytes. In addition, as an important industrial raw material, CO can be used as a key intermediate in a tandem reactor for the synthesis of multi-carbon products or directly for the preparation of syngas (CO + H2), which is a necessary raw material for the conversion of chemicals such as methanol, acetic acid, and dimethyl ether through the Fischer-Tropsch process. However, the development of highly efficient and stable CO2RR catalysts still faces many challenges, including the precise regulation of the adsorption energy of reaction intermediates, the long-term stability of catalytic active sites, and industrial scale-up.

[0003] Currently, single-atom catalysts such as Ni-N-C show good catalytic activity in CO2RR. However, due to the strong adsorption of Ni on CO2 intermediates, it is easy to cause catalyst deactivation or CO poisoning. In contrast, bimetallic catalysts can optimize the electronic structure through synergistic effects and balance the adsorption strength of intermediates, thereby improving catalytic activity and selectivity. Research shows that the introduction of Zn can regulate the d-band center of Ni, reduce the formation energy barriers of COOH and CO intermediates, and avoid catalyst deactivation caused by excessive adsorption. However, existing Ni-Zn bimetallic catalysts still have problems such as insufficient structural stability and unclear reaction mechanisms, which limit their practical applications. Therefore, there is an urgent need to develop an efficient, stable, and easily scalable Ni-Zn bimetallic catalyst to promote the industrialization process of CO2RR technology. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a nitrogen-doped carbon fiber loaded with Ni-Zn bimetal and its application in electrocatalytic reduction of carbon dioxide, and particularly relates to a nitrogen-doped carbon fiber catalyst loaded with Ni-Zn bimetal and its preparation and application.

[0005] The present invention provides a preparation method for a nitrogen-doped carbon fiber loaded with Ni-Zn bimetal, comprising:

[0006] (1) Mix polyacrylonitrile (PAN) and a solvent, pyrolyze, and after cooling, add zinc oxide (ZnO), zinc acetate (C4H6O4Zn·2H2O), and nickel acetate (C4H 14 NiO8), stir to obtain a spinning solution, and perform electrospinning to obtain a nanofiber composite membrane;

[0007] (2) Pre-oxidize the nanofiber composite membrane, then carbonize it under a nitrogen (N2) atmosphere, grind, wash, and dry to obtain nitrogen-doped carbon fibers loaded with Ni / Zn bimetals.

[0008] Preferably, in step (1), the solvent includes N,N-dimethylformamide (DMF); the ratio of polyacrylonitrile (PAN) to the solvent in step (1) is (0.5 - 2) g : (5 - 20) mL.

[0009] Preferably, the mass ratio of zinc oxide, zinc acetate, and nickel acetate in step (1) is 1:1:0.5 - 3.

[0010] The ratio of zinc oxide to the solvent in step (1) is (0.25 - 1) g : (5 - 20) mL.

[0011] Preferably, the pyrolysis in step (1) is carried out at 55 - 65 °C for 5 - 15 h; the stirring time is 5 - 15 h.

[0012] Preferably, the electrospinning process parameters in step (1) include: the electrospinning flow rate is 0.8 - 1.5 mL / h, the voltage provided by a high-power DC power supply is 12 - 20 kV, and the electrospinning duration is 3 - 12 h.

[0013] Preferably, the pre-oxidation in step (2) has a heating rate of 1 - 5 °C / min, is heated to 150 - 300 °C, and the holding time is 1 - 3 h.

[0014] Preferably, the carbonization in step (2) has a heating rate of 15 - 25 °C / min, is heated to 800 - 1100 °C, and the holding time is 1 - 3 h.

[0015] Preferably, the washing in step (2) is first pickling and then water washing and suction filtration; the pickling is immersing in 1 - 3 M hydrochloric acid for 6 - 12 h.

[0016] The present invention provides nitrogen-doped carbon fibers loaded with Ni-Zn bimetals prepared by the above method, wherein the diameter of the nitrogen-doped carbon fibers loaded with Ni-Zn bimetals is 80 - 120 nm, and the nitrogen-doped carbon fibers loaded with Ni-Zn bimetals have a heterostructure with Ni / Zn-N-C nanoparticles uniformly distributed in the carbon fibers, and the particle size of the Ni / Zn-N-C nanoparticles is 8 - 11 nm.

[0017] The present invention provides an electrocatalyst, and the electrocatalyst includes the nitrogen-doped carbon fiber loaded with Ni-Zn bimetal.

[0018] The present invention provides an application of the nitrogen-doped carbon fiber loaded with Ni-Zn bimetal or the electrocatalyst in electrocatalytic reduction of carbon dioxide, such as a zero-gap MEA reactor, an H-type electrolytic cell, etc.

[0019] The present invention provides a Ni-Zn bimetal catalyst supported on nitrogen-doped carbon nanofibers (CNFs), a preparation method thereof and an application thereof. The catalyst is prepared by an electrospinning combined with a high-temperature carbonization process, and has excellent CO2 electroreduction activity and long-term stability.

[0020] The present invention provides a heterostructure catalyst for electrocatalytic carbon dioxide reduction reaction. The catalyst is a Ni / Zn-N-C composite metal particle supported on nitrogen-doped carbon nanofibers and is prepared by an electrospinning strategy. The synergistic effect of Ni and Zn in the catalyst can optimize the adsorption performance of carbon dioxide intermediates, balance the strong binding affinity of Ni and the weaker affinity of Zn, and effectively prevent over-activation. The electron transfer inside the catalyst promotes the rapid electron transfer to carbon dioxide, so that it shows excellent catalytic performance in the carbon dioxide electrochemical reduction reaction. In a traditional H-type reactor, the Faraday efficiency of the catalyst for CO is close to 90% at a potential of -0.86 V vs. RHE, and the current density can reach 17.51 mA cm -2 , and can maintain stable catalytic activity during a 50-hour electrolysis process. Further in a membrane electrode assembly reactor, the catalyst achieves 91.7% FE at a battery voltage of -3 V CO , and the current density is as high as 200 mA cm at a high potential of -3.9 V -2 , showing good practical application prospects.

[0021] Beneficial effects

[0022] (1) The carbon nanofibers prepared by using the electrospinning technology have a high specific surface area, excellent electrical conductivity and adjustable porosity, and are a unique carbon carrier material. They not only promote the dispersion of metal particles and charge transfer, but also enhance the stability through Ni-Zn bonds and metal-N-C bonds, and still maintain a high catalytic activity after continuous electrolysis for 50 h; the micropores of the carbon substrate of the catalyst not only match the size of CO2 molecules (0.35 - 0.51 nm) relatively well, which is beneficial to the adsorption and enrichment of CO2, but also can confine the reaction intermediate (*COOH), thereby promoting the conversion of CO2 to CO. In addition, the introduction of N element further improves the electrical conductivity of the substrate;

[0023] (2) Through the Zn-Ni bimetallic synergistic regulation strategy, by constructing a NiZnC 0.7 heterostructure to achieve electron transfer, optimize the adsorption free energy of *COOH, and achieve a CO Faraday efficiency of nearly 90% at -0.86 V vs. RHE;

[0024] (3) Apply the Ni-Zn@CNFs catalyst to a zero-gap MEA reactor, and achieve an industrial-level current density of 200 mA cm -2 at a battery voltage of -3.9 V. This performance index has met the requirements of commercial applications, highlighting its potential for practical applications. Description of the Drawings

[0025] Figure 1 In (a) is the SEM image of the catalyst prepared in Example 1; (b) is the TEM image of the catalyst prepared in Example 1; (c) is the TEM-EDS image of the catalyst prepared in Example 1;

[0026] Figure 2 is the BET image of the catalyst prepared in Example 1;

[0027] Figure 3 is the XRD image of the catalysts prepared in Examples 1-3;

[0028] Figure 4 In (a) is the XPS spectrum of Ni 2p of the catalysts prepared in Examples 1-3; (b) is the XPS spectrum of Zn 2p of the catalysts prepared in Examples 1-3;

[0029] Figure 5 In (a) is the LSV image of the catalysts prepared in Examples 1-3; (b) is the FE image of the catalysts prepared in Examples 1-3 for catalytic reduction of carbon dioxide;

[0030] Figure 6 is the long-term stability test image of the catalysts prepared in Examples 1 and 2;

[0031] Figure 7 In (a) is the device diagram of the zero-gap MEA reactor; (b) is the i-t curve diagram measured for the catalyst prepared in Example 1 in the zero-gap MEA reactor; (c) is the FE image of the catalyst prepared in Example 1 for catalytic reduction of carbon dioxide in the zero-gap MEA reactor. Detailed Implementation Modes

[0032] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application. Related tests:

[0033] The products of the embodiments of the present invention were characterized by surface morphology using a scanning electron microscope (FESEM, S-4800) and a field emission transmission electron microscope (TEM, JEM-2100F).

[0034] Electrochemical performance test: It was completed using a CHI760E electrochemical workstation in cooperation with an H-type electrolytic cell reactor and a zero-gap MEA reactor. After the gas reacted in the cathode chamber, it entered a gas chromatograph (GC9790Ⅱ type) through the gas outlet for real-time on-line analysis of the products. The Faraday efficiency (FE) of the gas products was calculated using the following formula:

[0035]

[0036] where ν is the CO2 flow rate, c represents the volume concentration of different gas products at the reactor outlet, N represents the number of electrons transferred from one CO2 molecule to CO and H2, and j total represents the total current density.

[0037] Example 1

[0038] Step 1): Dissolve 1 g of polyacrylonitrile in 10 mL of N,N-dimethylformamide and carry out pyrolysis by vigorously stirring at 60 °C for 10 h;

[0039] Step 2): After the above solution was cooled to room temperature, 0.5 g of ZnO, 0.5 g of C4H6O4Zn·2H2O and 0.6 g of C4H 14 NiO8 were added, and stirring was continued at room temperature for 12 h to obtain a uniform mixture for electrospinning;

[0040] Step 3): Load the mixed solution into a plastic syringe with a stainless steel needle head, advance it at a flow rate of 1 mL / h, and carry out an electrospinning experiment for 10 h under a voltage of 20 kV provided by a high-power DC power supply;

[0041] Step 4): The nanofiber composite membrane obtained by electrospinning was placed in a muffle furnace, heated to 220 °C at a rate of 1 °C / min and held for 2 h for low-temperature pre-oxidation;

[0042] [[ID=3�]]Step 5): The pre-oxidized nanofiber composite membrane was placed in a tube furnace, heated to 900 °C at a rate of 20 °C / min under a N2 atmosphere and held for 1 h for high-temperature carbonization;

[0043] Step 6): Grind the obtained carbonized nanofiber composite membrane and immerse it in 1.0 M HCl solution for 8 h of pickling to remove excess metal nanoparticles; after the pickling reaction is completed, wash it with ultrapure water and then perform suction filtration and drying to obtain the Zn-Ni bimetallic catalyst supported on nitrogen-doped carbon nanofibers (Ni-Zn@CNFs).

[0044] Example 2

[0045] Step 1): Dissolve 1 g of polyacrylonitrile in 10 mL of N,N-dimethylformamide and vigorously stir at 60 °C for 10 h for pyrolysis;

[0046] Step 2): After the above solution is cooled to room temperature, add 0.6 g of C4H 14 NiO8 and continue to stir at room temperature for 12 h to obtain a homogeneous mixture for electrospinning;

[0047] Step 3): Load the mixed solution into a plastic syringe with a stainless steel needle and push it at a flow rate of 1 mL / h, and perform an electrospinning experiment for 10 h under a voltage of 20 kV provided by a high-power DC power supply;

[0048] Step 4): Heat the nanofiber composite membrane obtained by electrospinning in a muffle furnace to 220 °C at a rate of 1 °C / min and hold for 2 h for low-temperature pre-oxidation;

[0049] Step 5): Place the pre-oxidized nanofiber composite membrane in a tubular furnace, heat it to 900 °C at a rate of 20 °C / min under a N2 atmosphere and hold for 1 h for high-temperature carbonization;

[0050] Step 6): Grind the obtained carbonized nanofiber composite membrane and immerse it in 1.0 M HCl solution for 8 h of pickling to remove excess metal nanoparticles; after the pickling reaction is completed, wash it with ultrapure water and then perform suction filtration and drying to obtain the Ni catalyst supported on nitrogen-doped carbon nanofibers (Ni@CNFs).

[0051] Example 3

[0052] Step 1): Dissolve 1 g of polyacrylonitrile in 10 mL of N,N-dimethylformamide and vigorously stir at 60 °C for 10 h for pyrolysis;

[0053] Step 2): After the above solution is cooled to room temperature, add 0.5 g of ZnO and 0.5 g of C4H6O4Zn·2H2O, and continue to stir at room temperature for 12 h to obtain a homogeneous mixture for electrospinning;

[0054] Step 3): Load the mixed solution into a plastic syringe with a stainless-steel needle and push it at a flow rate of 1 mL / h. Conduct an electrospinning experiment for 10 h under a voltage of 20 kV provided by a high-power DC power supply;

[0055] Step 4): Place the nanofiber composite membrane obtained by electrospinning in a muffle furnace, heat it to 220 °C at a rate of 1 °C / min and hold for 2 h for low-temperature pre-oxidation;

[0056] Step 5): Place the pre-oxidized nanofiber composite membrane in a tubular furnace, heat it to 900 °C at a rate of 20 °C / min under a N2 atmosphere and hold for 1 h for high-temperature carbonization;

[0057] Step 6): Grind the obtained carbonized nanofiber composite membrane and immerse it in a 1.0 M HCl solution for 8 h of pickling to remove excess metal nanoparticles; after the pickling reaction, wash it with ultrapure water and then perform suction filtration and drying to obtain a Zn catalyst supported on nitrogen-doped carbon nanofibers (Zn@CNFs).

[0058] Catalytic application experiment:

[0059] Mix 10 mg of the catalysts prepared in Examples 1-3 with 100 μL of Nafion solution (5 wt%) and 2.5 mL of absolute ethanol respectively, and perform ultrasonic treatment for 30 min to form a uniformly dispersed catalyst slurry. Then, use a pneumatic spray gun to uniformly spray the slurry on the surface of a hydrophobic carbon paper substrate (1×1.5 cm 2 ) surface, and control the loading amount by real-time weighing during the spraying process. Finally, perform a combined drying treatment with a heating table and an infrared lamp to obtain a working electrode with a loading amount of 1 mg cm -2 and an effective catalytic area of 1×1 cm 2 .

[0060] Use the above-prepared electrode as the working electrode to test the selectivity of the catalysts prepared in Examples 1-3 for catalytic reduction of CO2 to CO in an H-type electrolytic cell. In the anodic chamber, 0.5 M KOH is used as the anodic electrolyte and a Pt sheet is used as the anode; in the cathodic chamber, 0.5 M KHCO3 is used as the cathodic electrolyte and an Ag / AgCl electrode is used as the reference electrode; an FAB-PK-130 anion exchange membrane is used as the electrolyte membrane.

[0061] Further apply this catalyst to the MEA reactor using the same loading method. Different from the H-type reactor, the effective area of the cathode in the MEA reactor is 2×2 cm 2 , and for the anode, IrO2 is loaded on a titanium felt (IrO2@Ti felt) using the same method.

[0062] As Figure 1a is the SEM image of the Ni-Zn@CNFs catalyst prepared in Example 1. It can be observed that the sample material presents the morphological characteristics of carbon nanofibers, and its diameter distribution range is 80-120 nm. Further high-resolution transmission electron microscopy (TEM) characterization ( Figure 1 b) clearly shows that the size of Ni / Zn-N-C nanoparticles is about 10 nm, which are uniformly distributed on the surface of carbon fibers. In addition, the TEM-EDS spectrum ( Figure 1 c) can observe that the active sites of Ni / Zn bimetals are uniformly distributed, which is due to the fact that the electrospinning technique can uniformly load metal nanoparticles on nitrogen-doped carbon nanofibers.

[0063] As Figure 2 is the BET diagram of the Ni-Zn@CNFs catalyst. The specific surface area and porous structure of Ni-Zn@CNFs were evaluated by CO2 adsorption-desorption analysis. Among them, according to Figure 2 it is known that the specific surface area of Ni-Zn@CNFs is 39.0 m 2 g -1 , which is attributed to the volatilization of metal Zn during the pyrolysis process. The volatilized metal Zn leaves a porous structure on the carbon fibers, while metal Ni hardly volatilizes. In addition, nickel acetate decomposes mildly during pyrolysis and tends to form porous or nanostructures, which is beneficial to increasing the specific surface area and exposing active sites. Regarding the porous structure, as shown in the inset of Figure 2 , the prominent peak at about 1.74 nm indicates that there are certain micropores and mesopores in Ni@CNFs. These micropores not only match the size of CO2 molecules (0.35-0.51 nm) well, which is beneficial to the adsorption and enrichment of CO2, but also can confine reaction intermediates (*COOH), thereby promoting the conversion of CO2 to CO.

[0064] As Figure 3 are the XRD patterns of the Zn@CNFs, Ni@CNFs, and Ni-Zn@CNFs catalysts prepared in Examples 1-3. Introducing ZnO and C4H6O4Zn·2H2O into the electrospinning solution enables the formation of Ni3ZnC with (111), (200), and (220) crystal planes in Ni-Zn@CNFs 0.7 , and their crystal planes are located at 42.78°, 49.78°, and 73.14° respectively.

[0065] As Figure 4 are the XPS spectra of the Zn@CNFs, Ni@CNFs, and Ni-Zn@CNFs catalysts prepared in Examples 1-3. As shown in Figure 4 a, the high-resolution Ni 2p spectra of Ni@CNFs and Ni-Zn@CNFs are at 855.1 eV (Ni 2p 3 / 2 ) and 872.8 eV (Ni2p1 / 2 ) shows two peaks, which can be decomposed into peaks corresponding to Ni 0 and Ni 2+ . Compared with Ni@CNFs, the Ni 2p 3 / 2 peak of Ni-Zn@CNFs shows a negative shift of 0.74 eV, indicating that due to the introduction of Zn, the Ni sites become electron acceptors. At the same time, Figure 3 The high-resolution Zn 2p spectra of Zn@CNFs and Ni-Zn@CNFs in b show two peaks at 1021.9 eV (Zn 2p 3 / 2 ) and 1044.9 eV (Zn 2p 1 / 2 ). Compared with Zn@CNFs, the Zn 2p 3 / 2 peak of Ni-Zn@CNFs is positively shifted by 0.65 eV, indicating that the Zn sites act as electron donors. Therefore, the electron transfer in Ni-Zn@CNFs is from the Zn sites to the Ni sites. Since electrons are rapidly transferred from the Ni sites to CO2, the accumulation of electrons on the Ni sites is beneficial to the reduction of CO2.

[0066] As Figure 5 a is the LSV diagram of the catalysts prepared in Examples 1-3. Compared with the N2-saturated condition, the LSV polarization curve of Ni-Zn@CNFs under CO2-saturated condition shows a higher current density, indicating its significant CO2 reduction activity. At -1.16 V vs. RHE, the current density of Ni-Zn@CNFs reaches 17.51 mA cm -2 , exceeding that of Zn@CNFs (13.24 mA cm -2 ) and Ni@CNFs (7.97 mA cm -2 ). At 2 mA cm -2 , the onset potential of Ni-Zn@CNFs is -0.68 V vs. RHE, lower than that of Zn@CNFs (-0.77 V vs. RHE) and Ni@CNFs (-0.83 V vs. RHE). Compared with Zn@CNFs and Ni@CNFs, Ni-Zn@CNFs has a lower onset potential and a higher current density at the same applied potential, highlighting its excellent CO2 reduction activity. Figure 5 b is the FE diagram of the catalysts prepared in Examples 1-3 for the catalytic reduction of carbon dioxide. The FE CO of Ni-Zn@CNFs rises from 36.9% to nearly 90% in the potential range of -0.56 to -0.76 V vs. RHE, much higher than that of Zn@CNFs and Ni@CNFs.

[0067] As Figure 6Long-term stability test diagram of the catalysts prepared in Examples 1 and 2. After Ni-Zn@CNFs were electrolyzed at a voltage of -0.86 V vs. RHE for 50 hours, its FE CO remained at about 90%, and the current density was 4 mA cm -2 . Although Ni@CNFs also showed good stability during the 50-hour electrolysis process, its current density and FE CO were both lower than those of Ni-Zn@CNFs.

[0068] As Figure 7 Figure a is the device diagram of the zero-gap MEA reactor. This configuration not only significantly reduces the ohmic resistance of the system and improves the Faraday efficiency, but also effectively enhances the mass transfer process and reduces the polarization effect through the synergistic effect of the flowing electrolyte and CO2 gas, thereby increasing the current density to a level that meets industrial requirements. Figure 7 Figure b is the i-t curve diagram of the catalyst prepared in Example 1 measured in the MEA reactor. When the applied potential exceeded -3.0 V, the current density of Ni-Zn@CNFs showed a significant increase. It is particularly noteworthy that at a high potential of -3.9 V, the total current density of the reactor could be as high as about 200 mA cm -2 , indicating that Ni-Zn@CNFs have excellent industrial potential. Figure 7 Figure b is the FE diagram of the catalyst prepared in Example 1 for catalytic reduction of carbon dioxide in the zero-gap MEA reactor. The FE of Ni-Zn@CNFs CO increased from 80.1% to 90.1% as the applied potential increased from -2.4 V to -3.0 V. Even under the high potential condition of -3.9 V, the FE CO could still remain at a relatively high level of 70.0%.

Claims

1. A preparation method of Ni-Zn bimetal-loaded nitrogen-doped carbon fiber, comprising: (1) Mix polyacrylonitrile (PAN) and a solvent, pyrolyze, cool, add zinc oxide, zinc acetate and nickel acetate, stir to obtain a spinning solution, and perform electrospinning to obtain a nanofiber composite membrane; (2) Pre-oxidize the nanofiber composite membrane, then carbonize it in a nitrogen (N2) atmosphere, grind, wash, and dry to obtain Ni-Zn bimetal-loaded nitrogen-doped carbon fiber.

2. The preparation method according to claim 1, characterized in that, In the step (1), the solvent includes N,N-dimethylformamide (DMF); the ratio of polyacrylonitrile (PAN) to the solvent in the step (1) is (0.5 - 2) g : (5 - 20) mL.

3. The preparation method according to claim 1, wherein In the step (1), the mass ratio of zinc oxide, zinc acetate and nickel acetate is 1:1:0.5 - 3.

4. The preparation method according to claim 1, characterized in that, In the step (1), the pyrolysis is carried out at 55 - 65 °C for 5 - 15 h; the stirring time is 5 - 15 h; In the step (1), the electrospinning process parameters include: the electrospinning flow rate is 0.8 - 1.5 mL / h, the voltage provided by a high-power DC power supply is 12 - 20 kV, and the electrospinning duration is 3 - 12 h.

5. The preparation method according to claim 1, characterized in that, In the step (2), the pre-oxidation has a heating rate of 1 - 5 °C / min, is heated to 150 - 300 °C, and the holding time is 1 - 3 h.

6. According to the preparation method described in claim 1, characterized in that, In the step (2), the carbonization has a heating rate of 15 - 25 °C / min, is heated to 800 - 1100 °C, and the holding time is 1 - 3 h.

7. According to the preparation method described in claim 1, characterized in that In the step (2), the washing is first acid washing and then water washing; the acid washing is to immerse in 1 - 3 M hydrochloric acid for 6 - 12 h.

8. A Ni-Zn bimetal-loaded nitrogen-doped carbon fiber prepared by the method according to claim 1.

9. An electrocatalyst, characterized in that, The electrocatalyst includes the Ni-Zn bimetal-loaded nitrogen-doped carbon fiber according to claim 8.

10. An application of the Ni-Zn bimetal-loaded nitrogen-doped carbon fiber according to claim 8 or the electrocatalyst according to claim 9 in the electrocatalytic reduction of carbon dioxide.

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