Bifunctional electrocatalyst of n, p co-doped porous carbon nanosheet supported feco hollow nanospheres and preparation method and application thereof

Abstract

The application discloses a bifunctional electrocatalyst of N and P co-doped porous carbon nanosheet loaded FeCo hollow nanospheres and a preparation method and application thereof. The preparation method is as follows: nitrogen-doped carbon materials are prepared through grinding and mixing and high-temperature pyrolysis. Pluronic F-127, the nitrogen-doped carbon materials, iron nitrate, cobalt nitrate, melamine and o-phenylenediamine are added into an ethanol solution to be mixed, ultrasonically treated and stirred, and after reaction, the solution is evaporated, high-temperature pyrolysis and sodium hypophosphite phosphorization are carried out, and finally the bifunctional electrocatalyst of N and P co-doped porous carbon nanosheet loaded FeCo hollow nanospheres is obtained. The catalyst can exhibit excellent catalytic activity in electrocatalytic oxygen reduction reaction and oxygen evolution reaction, and can be applied in a liquid zinc-air battery.

Description

Technical Field

[0001] This invention belongs to the field of new energy technology, specifically relating to bifunctional electrocatalysts of FeCo hollow nanospheres supported on N and P co-doped porous carbon nanosheets, their preparation methods, and applications. Background Technology

[0002] Energy is one of the most pressing problems facing humanity, and converting various new energy sources into electrical energy for storage is a common energy storage method. Metal-air batteries are a promising chemical energy storage device, and zinc-air batteries, as one type of metal-air battery, have a higher theoretical energy density than lithium-ion batteries and are expected to become a next-generation chemical power source. The anode of a zinc-air battery consists of a high-purity zinc plate or foil, while the cathode material consists of a current collector, a gas diffusion layer, and a catalyst layer. Oxygen reduction (ORR) and oxygen evolution reaction (OER) occur on the air cathode. The kinetics of OR and OER on the air cathode are slow, so zinc-air batteries require the use of noble metals such as Pt, Ru, and Ir for catalysis. However, the high cost of noble metals limits the large-scale use of zinc-air batteries. Non-noble metal catalysts, represented by transition metals such as Fe, Ni, Mn, Co, Cu, and Mo, are abundant and inexpensive. Their catalytic activity is similar to that of noble metal catalysts, and they possess higher corrosion resistance, methanol poisoning resistance, and stability. Therefore, it is necessary to develop low-cost and highly efficient bifunctional transition metal electrocatalysts to replace noble metal catalysts.

[0003] Metal-nitrogen-carbon materials are widely considered to be excellent catalysts for oxygen exchange rate (ORR), as the formation of metal-nitrogen coordination can significantly enhance electrocatalytic performance. For example, Fe-NC materials, based on their Fe-N coordination structure, exhibit extremely superior catalytic performance in ORR, outperforming commercial Pt / C catalysts. However, the OER catalytic efficiency of most Fe-NC materials reported in the literature is not entirely satisfactory, while transition metal alloys (such as FeCo and FeNi alloys) can exhibit excellent ORR / OER performance. A Chinese patent application, "Preparation and Application of Nickel-Iron Alloy / Nitrogen-Doped Carbon Fiber as an Oxygen Electrocatalyst for Zinc-Air Batteries," discloses a bifunctional catalyst material of nickel-iron alloy nanoparticles supported on nitrogen-doped carbon fibers, which exhibits good ORR / OER performance. However, its preparation method requires etching the raw materials with a strong alkali and precise adjustment of the potassium hydroxide concentration, followed by hydrothermal and high-temperature pyrolysis methods to obtain the final catalyst material, making the overall preparation conditions quite complex. Therefore, developing simpler, more efficient, safer, and more environmentally friendly methods for preparing transition metal alloy bifunctional electrocatalysts remains a challenge.

[0004] The loose, porous structure of catalysts facilitates oxygen adsorption and electrochemical kinetics, providing an effective conduction network for rapid electron diffusion and leading to more catalytically active sites, thus improving the efficiency of bifunctional electrocatalysis. A Chinese patent application, "A Bifunctional Catalytic Material and Its Preparation Method and Application," reports a method for fabricating porous structures using NaCl as a template. This method can create hierarchical porous structures of macropores, mesopores, and micropores, which is beneficial to catalyst performance. However, the preparation method requires temperatures of 1000℃ or even higher and necessitates the removal of the template using inorganic acids, making it environmentally unfriendly and hazardous. Therefore, developing simpler, safer, and more efficient methods for preparing loosely porous ORR / OER bifunctional electrocatalysts is more conducive to the large-scale development of zinc-air batteries. Summary of the Invention

[0005] Based on existing technical problems, the purpose of this invention is to provide a bifunctional electrocatalyst consisting of N / P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres, along with its preparation method and applications. The method provided by this invention has advantages such as high safety, low cost, simplicity, environmental friendliness, and high stability.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0007] This invention provides a method for preparing a bifunctional electrocatalyst consisting of N and P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres, comprising the following steps:

[0008] (1) Preparation of nitrogen-doped carbon materials: Purchased Ketjen black and melamine were ground and mixed, and then calcined at high temperature in a tube furnace to obtain nitrogen-doped carbon materials (NC).

[0009] (2) Pluronic F-127, nitrogen-doped carbon material and melamine were ultrasonically dispersed in an ethanol solution to obtain solution A; iron nitrate, cobalt nitrate and o-phenylenediamine were ultrasonically dissolved in an ethanol solution to obtain solution B, and solution B was slowly added dropwise to solution A and mixed and stirred. After the reaction, the mixture was evaporated to dryness and placed in a tube furnace for high-temperature calcination to obtain f-FeCo / NC precursor powder (black powder).

[0010] (3) Preparation of f-FeCo / NPC: The f-FeCo / NC precursor powder was ground uniformly and calcined and phosphated in a tube furnace using sodium hypophosphite to obtain a bifunctional electrocatalyst (f-FeCo / NPC) supported on N and P co-doped porous carbon nanosheets.

[0011] Further, in step (1), the Ketjen black is a conductive carbon black, and the mass ratio of Ketjen black to melamine is 1:(10-20).

[0012] Preferably, the mass ratio of Ketjen black to melamine in step (1) is 1:10.

[0013] Further, the calcination temperature in step (1) is 800℃-900℃, the heating rate in step (1) is 2.9-3.1℃ / min, the calcination time in step (1) is 2-3 hours, and the protective gas in step (1) is either argon or nitrogen.

[0014] Preferably, the calcination temperature in step (1) is 900°C, the heating rate in step (1) is 3°C / min, and the calcination time is 2 hours.

[0015] Further, in step (2), the volume of ethanol solution added to solution A is 20-30 mL, and the volume of ethanol solution added to solution B is 5-10 mL. The mass ratio of ferric nitrate to nitrogen-doped carbon material is (1-2):1, the molar ratio of ferric nitrate to cobalt nitrate is (1-2):1, the mass ratio of ferric nitrate to the volume of ethanol solution added to solution B is 0.01-0.02 g / mL, the mass ratio of Pluronic F-127 to the volume ratio of ethanol solution added to solution A is 0.01-0.02 g / mL, the mass ratio of melamine to the volume ratio of ethanol solution added to solution A is 0.050-0.075 g / mL, and the mass ratio of o-phenylenediamine to the volume ratio of ethanol solution added to solution B is 0.02-0.04 g / mL.

[0016] Preferably, the mass ratio of ferric nitrate to nitrogen-doped carbon material in step (2) is 1:1, the mass ratio of ferric nitrate to cobalt nitrate in step (2) is 1:1, the mass ratio of ferric nitrate to the volume of ethanol solution added to solution B in step (2) is 0.01 g / mL, and the mass ratio of o-phenylenediamine to the volume of ethanol solution added to solution B in step (2) is 0.02 g / mL.

[0017] Furthermore, the ultrasound time in step (2) is 30-50 min; the stirring time in step (2) is 2-3 hours.

[0018] Preferably, the ultrasonic time in step (2) is 40 minutes, and the stirring time in step (2) is 2 hours.

[0019] Furthermore, the temperature for evaporation in step (2) is 70℃-90℃, and the evaporation time in step (2) is 3-6 hours.

[0020] Preferably, the temperature for evaporation in step (2) is 70°C, and the evaporation time in step (2) is 6 hours.

[0021] Further, in step (2), the calcination is divided into two stages. The first stage is to heat the temperature to 300℃-350℃ at a heating rate of 1.9-2.1℃ / min and hold it for 2-3 hours. The second stage is to heat the temperature to 800℃-850℃ at a heating rate of 1.9-2.1℃ / min and hold it for 2-3 hours. The protective gas for the calcination is either argon or nitrogen.

[0022] Preferably, in step (2), the first stage of calcination is to heat to 350°C at a heating rate of 2°C / min and hold for 2 hours, and the second stage of calcination is to heat to 800°C at a heating rate of 2°C / min and hold for 2 hours.

[0023] Further, the mass ratio of the f-FeCo / NC precursor and sodium hypophosphite in step (3) is 1:(10-15).

[0024] Preferably, the mass ratio of the f-FeCo / NC precursor to sodium hypophosphite in step (3) is 1:10.

[0025] Further, the calcination temperature in step (3) is 300℃-350℃, the heating rate in step (3) is 2.9-3.1℃ / min, the calcination time in step (3) is 2-3 hours, and the protective gas in step (3) is either argon or nitrogen.

[0026] Preferably, the calcination temperature in step (3) is 350°C, the heating rate in step (3) is 3°C / min, and the calcination time in step (3) is 2 hours.

[0027] This invention provides a bifunctional electrocatalyst for N, P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres, prepared by the aforementioned method.

[0028] The present invention also provides the application of the bifunctional electrocatalyst of FeCo hollow nanospheres supported on N and P co-doped porous carbon nanosheets in electrocatalytic oxygen reduction reaction or electrocatalytic oxygen evolution reaction.

[0029] Furthermore, the bifunctional electrocatalyst, consisting of N and P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres, is drop-coated onto a glassy carbon electrode as the working electrode, silver-silver chloride as the reference electrode, platinum wire as the counter electrode, and potassium hydroxide solution as the electrolyte, and the electrocatalytic reaction is carried out in a five-cell electrolytic cell.

[0030] Furthermore, the concentration of the potassium hydroxide solution is 0.1 M in the electrocatalytic oxygen reduction reaction and 1.0 M in the electrocatalytic oxygen evolution reaction.

[0031] Furthermore, the bifunctional electrocatalyst of N,P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres is applied in the preparation of zinc-air battery cathode materials.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] (1) The bifunctional electrocatalyst of FeCo hollow nanospheres supported on N and P co-doped porous carbon nanosheets provided by the present invention has a simple preparation method, low raw material cost, high safety, mild preparation conditions, and is conducive to large-scale production.

[0034] (2) The bifunctional electrocatalyst of N and P co-doped porous carbon nanosheets supported on FeCo hollow nanospheres prepared in this invention uses Pluronic F-127 as a template, has a high specific surface area, and forms a large number of catalytic active sites. The nitrogen and phosphorus co-doped heterostructure increases the electrochemical performance of carbon materials.

[0035] (3) The bifunctional electrocatalyst of N and P co-doped porous carbon nanosheets supported on FeCo hollow nanospheres prepared in this invention forms a loose and porous carbon nanosheet structure and generates a large number of active sites such as Fe single atoms, Co single atoms and FeCo alloy nanoparticles. It is beneficial to the adsorption of oxygen molecules and the desorption of OH*. It exhibits excellent catalytic performance in the oxygen reduction reaction (ORR), which is comparable to the performance of commercial Pt / C catalysts, and has better stability and resistance to methanol poisoning.

[0036] (4) The bifunctional electrocatalyst prepared by the present invention, which is composed of N and P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres, forms active sites such as FeCo alloy, FeP and CoP nanoparticles, which is beneficial to reducing the overpotential of oxygen evolution reaction (OER) and has good bifunctional electrocatalytic activity.

[0037] (5) The bifunctional electrocatalyst of N and P co-doped porous carbon nanosheets supported on FeCo hollow nanospheres prepared in this invention is applied to the cathode material of zinc-air battery. The assembled zinc-air battery has a high open circuit voltage and power density.

[0038] (6) This invention employs a simple and controllable preparation process. Using Pluronic F-127 as a soft template, a porous bifunctional electrocatalyst rich in iron-cobalt hollow nanospheres was prepared, exhibiting excellent catalytic performance in both oxygen reduction and oxygen evolution reactions. The catalyst achieves a half-wave potential of 0.85 V vs RHE in the oxygen reduction catalytic reaction and a half-wave potential of 10 mA cm⁻¹ in the oxygen evolution reaction. -2The overpotential at the specified current density is only 310 mV. The bifunctional electrocatalyst, consisting of N / P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres prepared in this invention, was assembled into a liquid zinc-air battery. The open-circuit voltage of the liquid zinc-air battery can reach 1.505 V, and the highest power density can reach 150.5 mW / cm². -2 . Attached Figure Description

[0039] Figure 1 The image shows the SEM characterization of the bifunctional electrocatalyst (f-FeCo / NPC) consisting of N and P co-doped porous carbon nanosheets supported on FeCo hollow nanospheres, prepared in Example 1.

[0040] Figure 2 The image shows the TEM characterization of the bifunctional electrocatalyst (f-FeCo / NPC) supported on N and P co-doped porous carbon nanosheets and FeCo hollow nanospheres prepared in Example 1.

[0041] Figure 3 The ORR polarization curves of the bifunctional electrocatalyst (f-FeCo / NPC) prepared in Example 1 (N, P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres), f-Fe / NPC prepared in Comparative Example 1, f-Co / NPC prepared in Comparative Example 2, and commercial Pt / C in 0.1 MkOH solution at a scan rate of 5 mV / s are shown.

[0042] Figure 4 The image shows the it curve of the bifunctional electrocatalyst (f-FeCo / NPC) prepared in Example 1, consisting of N and P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres, in 0.1 M KOH solution.

[0043] Figure 5 The image shows the it curve of the bifunctional electrocatalyst (f-FeCo / NPC) prepared in Example 1, which is composed of N and P co-doped porous carbon nanosheets and FeCo hollow nanospheres, after the addition of methanol to 0.1 MkOH solution.

[0044] Figure 6 The OER polarization curves of the bifunctional electrocatalyst (f-FeCo / NPC) prepared in Example 1 (N, P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres), f-Fe / NPC prepared in Comparative Example 1, f-Co / NPC prepared in Comparative Example 2, and RuO2 / C in 1.0 MkOH solution at a scan rate of 5 mV / s are shown.

[0045] Figure 7The image shows the it curve of the bifunctional electrocatalyst (f-FeCo / NPC) prepared in Example 1, consisting of N and P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres, in 1.0 M KOH solution.

[0046] Figure 8 The graph shows the open-circuit potential and power density of a liquid zinc-air battery assembled with the bifunctional electrocatalyst (f-FeCo / NPC) of N, P co-doped porous carbon nanosheets supported on FeCo hollow nanospheres prepared in Example 1, under alkaline conditions. Detailed Implementation

[0047] The present invention will be further described in detail below through specific embodiments. These embodiments will enable those skilled in the art to have a more comprehensive understanding of the present invention, but will not limit the present invention in any way.

[0048] Example 1

[0049] This embodiment provides a method for preparing a bifunctional electrocatalyst (f-FeCo / NPC) of N,P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres. The preparation method includes the following steps:

[0050] (1) Preparation of nitrogen-doped carbon materials (NC):

[0051] 0.5g of Ketjen Black and 5.0g of melamine were weighed and ground evenly in a clean agate mortar. The mixture was then placed in a porcelain boat and calcined in a tube furnace at 900℃ for 2 hours under a nitrogen atmosphere. The nitrogen-doped carbon material was collected and named NC. The calcination heating rate was 3℃ / min. -1 .

[0052] (2) Disperse 100 mg of NC, 0.5 g of Pluronic F-127, and 1.5 g of melamine in 25 mL of ethanol by ultrasonication for 40 min to obtain dispersion A; dissolve 100 mg of Fe(NO3)3·9H2O, an equal amount of Co(NO3)2·6H2O, and 200 mg of o-phenylenediamine in 10 mL of ethanol by ultrasonication for 40 min to obtain solution B. Then, add solution B dropwise to solution A and stir for 2 hours to mix and disperse evenly. Heat the mixed solution system at 70 °C in an oil bath for 6 hours to evaporate to dryness, place it in an oven to dry completely, and then grind it to obtain the iron-cobalt bifunctional catalyst precursor. Load the obtained iron-cobalt bifunctional catalyst precursor into a ceramic boat and place it in a tube furnace. Under nitrogen protection, heat at 2 °C for 2 min. -1 The heating rate was increased to 350℃ and held for 2 hours, then increased by 2℃ / min. -1 The temperature was increased to 800℃ and held for 2 hours. After complete carbonization, the temperature was reduced to room temperature to obtain the sample, which was then ground uniformly and labeled as f-FeCo / NC.

[0053] (3) Place f-FeCo / NC and sodium hypophosphite in two ceramic boats at a mass ratio of 1:10 and place them in a tube furnace. Place the ceramic boat containing sodium hypophosphite at the upper air inlet and the ceramic boat containing f-FeCo / NC at the lower air inlet. Under nitrogen protection, incubate at 3℃ for 3 min. -1 The temperature was increased to 350℃ and held for two hours to obtain the bifunctional electrocatalyst (f-FeCo / NPC) supported on N,P co-doped porous carbon nanosheets with FeCo hollow nanospheres.

[0054] Figure 1 This is a scanning electron microscope (SEM) image of the bifunctional electrocatalyst (f-FeCo / NPC) supported on N,P co-doped porous carbon nanosheets, obtained in Example 1. Figure 1 It can be observed that the bifunctional electrocatalyst (f-FeCo / NPC) obtained in this invention exhibits a loose and porous carbon nanosheet structure. This loose and porous structure can increase the specific surface area of ​​the catalyst material, which is beneficial to exposing more catalytic active sites. Figure 2 This is a transmission electron microscope (TEM) image of the bifunctional electrocatalyst (f-FeCo / NPC) supported on N,P co-doped porous carbon nanosheets and FeCo hollow nanospheres obtained in Example 1. Figure 2 As can be seen from the above, the bifunctional electrocatalyst (f-FeCo / NPC) obtained in this invention has many hollow FeCo nanospheres loaded on the N and P co-doped carbon nanosheet substrate. This special hollow nanosphere structure is beneficial to improving the utilization rate of catalytic active sites. The formation of these hollow nanospheres can improve the ORR and OER electrocatalytic activity of the catalyst material and help increase the stability of the catalyst.

[0055] Example 2

[0056] This embodiment provides a method for preparing a bifunctional electrocatalyst (f-FeCo / NPC) of N,P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres. The preparation method includes the following steps:

[0057] (1) Preparation of nitrogen-doped carbon materials (NC):

[0058] 0.5g of Ketjen Black and 5.0g of melamine were weighed and ground evenly in a clean agate mortar. The mixture was then placed in a porcelain boat and calcined in a tube furnace at 850℃ for 2.5 hours under a nitrogen atmosphere. The nitrogen-doped carbon material was collected and named NC. The calcination heating rate was 3℃ / min. -1 .

[0059] (2) Disperse 100 mg of NC, 0.2 g of Pluronic F-127, and 1.5 g of melamine in 20 mL of ethanol by ultrasonication for 30 min to obtain dispersion A; dissolve 100 mg of Fe(NO3)3·9H2O, an equal amount of Co(NO3)2·6H2O, and 200 mg of o-phenylenediamine in 10 mL of ethanol by ultrasonication for 30 min to obtain solution B. Then, add solution B dropwise to solution A and stir for 2.5 hours to mix and disperse evenly. Heat the mixed solution system at 80 °C in an oil bath for 4.5 hours to evaporate to dryness, place it in an oven to dry completely, and then grind it to obtain the iron-cobalt bifunctional catalyst precursor. Load the obtained iron-cobalt bifunctional catalyst precursor into a ceramic boat and place it in a tube furnace. Under nitrogen protection, heat at 2 °C for 1 min. -1 The temperature was increased to 300℃ and held for 2.5 hours, then increased at a rate of 2℃ / min. -1 The temperature was increased to 850℃ and held for 2.5 hours. After complete carbonization, the temperature was reduced to room temperature to obtain the sample, which was then ground uniformly and labeled as f-FeCo / NC.

[0060] (3) Place f-FeCo / NC and sodium hypophosphite in two ceramic boats at a mass ratio of 1:10 and place them in a tube furnace. Place the ceramic boat containing sodium hypophosphite at the upper air inlet and the ceramic boat containing f-FeCo / NC at the lower air inlet. Under nitrogen protection, incubate at 3℃ for 3 min. -1 The temperature was increased to 350℃ and held for two hours to obtain the bifunctional electrocatalyst (f-FeCo / NPC) supported on N,P co-doped porous carbon nanosheets with FeCo hollow nanospheres.

[0061] Example 3

[0062] This embodiment provides a method for preparing a bifunctional electrocatalyst (f-FeCo / NPC) of N,P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres. The preparation method includes the following steps:

[0063] (1) Preparation of nitrogen-doped carbon materials (NC):

[0064] 0.5g of Ketjen Black and 5.0g of melamine were weighed and ground evenly in a clean agate mortar. The mixture was then placed in a porcelain boat and calcined in a tube furnace at 800℃ for 3 hours under a nitrogen atmosphere. The nitrogen-doped carbon material was collected and named NC. The calcination heating rate was 3℃ / min. -1 .

[0065] (2) Disperse 100 mg of NC, 0.45 g of Pluronic F-127, and 1.5 g of melamine in 30 mL of ethanol by ultrasonication for 50 min to obtain dispersion A; dissolve 100 mg of Fe(NO3)3·9H2O, an equal amount of Co(NO3)2·6H2O, and 200 mg of o-phenylenediamine in 10 mL of ethanol by ultrasonication for 50 min to obtain solution B. Then, add solution B dropwise to solution A and stir for 3 hours to mix and disperse evenly. Heat the mixed solution system at 90 °C in an oil bath for 3 hours to evaporate to dryness, place it in an oven to dry completely, and then grind it to obtain the iron-cobalt bifunctional catalyst precursor. Load the obtained iron-cobalt bifunctional catalyst precursor into a ceramic boat and place it in a tube furnace. Under nitrogen protection, heat at 2 °C for 1 min. -1 The heating rate was increased to 350℃ and held for 3 hours, then increased by 2℃ / min. -1 The temperature was increased to 800℃ and held for 3 hours. After complete carbonization, the temperature was reduced to room temperature to obtain the sample, which was then ground uniformly and labeled as f-FeCo / NC.

[0066] (3) Place f-FeCo / NC and sodium hypophosphite in two ceramic boats at a mass ratio of 1:10 and place them in a tube furnace. Place the ceramic boat containing sodium hypophosphite at the upper air inlet and the ceramic boat containing f-FeCo / NC at the lower air inlet. Under nitrogen protection, incubate at 3℃ for 3 min. -1 The temperature was increased to 350℃ and held for two hours to obtain the bifunctional electrocatalyst (f-FeCo / NPC) supported on N,P co-doped porous carbon nanosheets with FeCo hollow nanospheres.

[0067] Example 4

[0068] This embodiment provides a method for preparing a bifunctional electrocatalyst (f-FeCo / NPC) of N,P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres. The preparation method includes the following steps:

[0069] (1) Preparation of nitrogen-doped carbon materials (NC):

[0070] 0.5g of Ketjen Black and 10g of melamine were weighed and ground evenly in a clean agate mortar. The mixture was then placed in a porcelain boat and calcined in a tube furnace at 900℃ for 2 hours under a nitrogen atmosphere. The nitrogen-doped carbon material was collected and named NC. The calcination heating rate was 3℃ / min. -1 .

[0071] (2) Disperse 50 mg of NC, 0.5 g of Pluronic F-127, and 1.5 g of melamine in 25 mL of ethanol by ultrasonication for 40 min to obtain dispersion A; dissolve 100 mg of Fe(NO3)3·9H2O and 0.5 times the amount of Fe(NO3)3·9H2O in Co(NO3)2·6H2O and 200 mg of o-phenylenediamine in 5 mL of ethanol by ultrasonication for 40 min to obtain solution B. Then, add solution B dropwise to solution A and stir for 2 hours to mix and disperse evenly. Heat the mixed solution system at 70 °C in an oil bath for 6 hours to evaporate to dryness, place it in an oven to dry completely, and then grind it to obtain the iron-cobalt bifunctional catalyst precursor. Load the obtained iron-cobalt bifunctional catalyst precursor into a ceramic boat and place it in a tube furnace. Under nitrogen protection, heat at 2 °C for 2 min. -1 The heating rate was increased to 350℃ and held for 2 hours, then increased by 2℃ / min. -1 The temperature was increased to 800℃ and held for 2 hours. After complete carbonization, the temperature was reduced to room temperature to obtain the sample, which was then ground uniformly and labeled as f-FeCo / NC.

[0072] (3) Place f-FeCo / NC and sodium hypophosphite in two ceramic boats at a mass ratio of 1:10 and place them in a tube furnace. Place the ceramic boat containing sodium hypophosphite at the upper air inlet and the ceramic boat containing f-FeCo / NC at the lower air inlet. Under nitrogen protection, incubate at 3℃ for 3 min. -1 The temperature was increased to 350℃ and held for two hours to obtain the bifunctional electrocatalyst (f-FeCo / NPC) supported on N,P co-doped porous carbon nanosheets with FeCo hollow nanospheres.

[0073] Example 5

[0074] This embodiment provides a method for preparing a bifunctional electrocatalyst (f-FeCo / NPC) of N,P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres. The preparation method includes the following steps:

[0075] (1) Preparation of nitrogen-doped carbon materials (NC):

[0076] 0.5g of Ketjen Black and 5.0g of melamine were weighed and ground evenly in a clean agate mortar. The mixture was then placed in a porcelain boat and calcined in a tube furnace at 900℃ for 2 hours under a nitrogen atmosphere. The nitrogen-doped carbon material was collected and named NC. The calcination heating rate was 3℃ / min. -1 .

[0077] (2) Disperse 100 mg of NC, 0.5 g of Pluronic F-127, and 1.5 g of melamine in 25 mL of ethanol by ultrasonication for 40 min to obtain dispersion A; dissolve 100 mg of Fe(NO3)3·9H2O, an equal amount of Co(NO3)2·6H2O, and 200 mg of o-phenylenediamine in 10 mL of ethanol by ultrasonication for 40 min to obtain solution B. Then, add solution B dropwise to solution A and stir for 2 hours to mix and disperse evenly. Heat the mixed solution system at 70 °C in an oil bath for 6 hours to evaporate to dryness, place it in an oven to dry completely, and then grind it to obtain the iron-cobalt bifunctional catalyst precursor. Load the obtained iron-cobalt bifunctional catalyst precursor into a ceramic boat and place it in a tube furnace. Under nitrogen protection, heat at 2 °C for 2 min. -1 The heating rate was increased to 350℃ and held for 2 hours, then increased by 2℃ / min. -1 The temperature was increased to 800℃ and held for 2 hours. After complete carbonization, the temperature was reduced to room temperature to obtain the sample, which was then ground uniformly and labeled as f-FeCo / NC.

[0078] (3) Place f-FeCo / NC and sodium hypophosphite in two ceramic boats at a mass ratio of 1:15 and place them in a tube furnace. Place the ceramic boat containing sodium hypophosphite at the upper air inlet and the ceramic boat containing f-FeCo / NC at the lower air inlet. Under nitrogen protection, incubate at 3℃ for 3 min. -1 The temperature was increased to 350℃ and held for two hours to obtain the bifunctional electrocatalyst (f-FeCo / NPC) supported on N,P co-doped porous carbon nanosheets with FeCo hollow nanospheres.

[0079] Example 6

[0080] This embodiment provides a method for preparing a bifunctional electrocatalyst (f-FeCo / NPC) of N,P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres. The preparation method includes the following steps:

[0081] (1) Preparation of nitrogen-doped carbon materials (NC):

[0082] 0.5g of Ketjen Black and 5.0g of melamine were weighed and ground evenly in a clean agate mortar. The mixture was then placed in a porcelain boat and calcined in a tube furnace at 900℃ for 2 hours under a nitrogen atmosphere. The nitrogen-doped carbon material was collected and named NC. The calcination heating rate was 3℃ / min. -1 .

[0083] (2) Disperse 100 mg of NC, 0.5 g of Pluronic F-127, and 1.5 g of melamine in 25 mL of ethanol by ultrasonication for 40 min to obtain dispersion A; dissolve 100 mg of Fe(NO3)3·9H2O, an equal amount of Co(NO3)2·6H2O, and 200 mg of o-phenylenediamine in 10 mL of ethanol by ultrasonication for 40 min to obtain solution B. Then, add solution B dropwise to solution A and stir for 2 hours to mix and disperse evenly. Heat the mixed solution system at 70 °C in an oil bath for 6 hours to evaporate to dryness, place it in an oven to dry completely, and then grind it to obtain the iron-cobalt bifunctional catalyst precursor. Load the obtained iron-cobalt bifunctional catalyst precursor into a ceramic boat and place it in a tube furnace. Under nitrogen protection, heat at 2 °C for 2 min. -1 The heating rate was increased to 350℃ and held for 2 hours, then increased by 2℃ / min. -1 The temperature was increased to 800℃ and held for 2 hours. After complete carbonization, the temperature was reduced to room temperature to obtain the sample, which was then ground uniformly and labeled as f-FeCo / NC.

[0084] (3) Place f-FeCo / NC and sodium hypophosphite in two ceramic boats at a mass ratio of 1:15 and place them in a tube furnace. Place the ceramic boat containing sodium hypophosphite at the upper air inlet and the ceramic boat containing f-FeCo / NC at the lower air inlet. Under nitrogen protection, incubate at 3℃ for 3 min. -1 The temperature was increased to 300℃ and held for three hours to obtain the bifunctional electrocatalyst (f-FeCo / NPC) supported on N,P co-doped porous carbon nanosheets with FeCo hollow nanospheres.

[0085] Example 7

[0086] This embodiment provides a method for preparing a bifunctional electrocatalyst (f-FeCo / NPC) of N,P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres. The preparation method includes the following steps:

[0087] (1) Preparation of nitrogen-doped carbon materials (NC):

[0088] 0.5g of Ketjen Black and 5.0g of melamine were weighed and ground evenly in a clean agate mortar. The mixture was then placed in a porcelain boat and calcined in a tube furnace at 900℃ for 2 hours under a nitrogen atmosphere. The nitrogen-doped carbon material was collected and named NC. The calcination heating rate was 3℃ / min. -1 .

[0089] (2) Disperse 100 mg of NC, 0.5 g of Pluronic F-127, and 1.5 g of melamine in 25 mL of ethanol by ultrasonication for 40 min to obtain dispersion A; dissolve 100 mg of Fe(NO3)3·9H2O, an equal amount of Co(NO3)2·6H2O, and 200 mg of o-phenylenediamine in 10 mL of ethanol by ultrasonication for 40 min to obtain solution B. Then, add solution B dropwise to solution A and stir for 2 hours to mix and disperse evenly. Heat the mixed solution system at 70 °C in an oil bath for 6 hours to evaporate to dryness, place it in an oven to dry completely, and then grind it to obtain the iron-cobalt bifunctional catalyst precursor. Load the obtained iron-cobalt bifunctional catalyst precursor into a ceramic boat and place it in a tube furnace. Under nitrogen protection, heat at 2 °C for 2 min. -1 The heating rate was increased to 350℃ and held for 2 hours, then increased by 2℃ / min. -1 The temperature was increased to 800℃ and held for 2 hours. After complete carbonization, the temperature was reduced to room temperature to obtain the sample, which was then ground uniformly and labeled as f-FeCo / NC.

[0090] (3) Place f-FeCo / NC and sodium hypophosphite in two ceramic boats at a mass ratio of 1:10 and place them in a tube furnace. Place the ceramic boat containing sodium hypophosphite at the upper air inlet and the ceramic boat containing f-FeCo / NC at the lower air inlet. Under nitrogen protection, incubate at 3℃ for 3 min. -1 The temperature was increased to 350℃ and held for 2.5 hours to obtain the bifunctional electrocatalyst (f-FeCo / NPC) supported on N,P co-doped porous carbon nanosheets with FeCo hollow nanospheres.

[0091] Comparative Example 1

[0092] This embodiment provides a method for preparing a loose and porous iron metal electrocatalyst (f-Fe / NPC), the preparation method comprising the following steps:

[0093] (1) Preparation of nitrogen-doped carbon materials (NC):

[0094] 0.5g of Ketjen Black and 5.0g of melamine were weighed and ground evenly in a clean agate mortar. The mixture was then placed in a porcelain boat and calcined in a tube furnace at 900℃ for 2 hours under a nitrogen atmosphere. The nitrogen-doped carbon material was collected and named NC. The calcination heating rate was 3℃ / min. -1 .

[0095] (2) Disperse 100 mg of NC, 0.5 g of Pluronic F-127, and 1.5 g of melamine in 25 mL of ethanol by ultrasonication for 40 min to obtain dispersion A; dissolve 100 mg of Fe(NO3)3·9H2O and 200 mg of o-phenylenediamine in 10 mL of ethanol by ultrasonication for 40 min to obtain solution B. Then, add solution B dropwise to solution A and stir for 2 hours to mix and disperse evenly. Heat the mixed solution system at 70 °C in an oil bath for 6 hours to evaporate to dryness, place it in an oven to dry completely, and then grind it to obtain the iron-metal bifunctional catalyst precursor. Load the obtained iron-metal bifunctional catalyst precursor into a ceramic boat and place it in a tube furnace. Under nitrogen protection, heat at 2 °C for 2 min. -1 The heating rate was increased to 350℃ and held for 2 hours, then increased by 2℃ / min. -1 The temperature was increased to 800℃ and held for 2 hours. After complete carbonization, the temperature was reduced to room temperature to obtain the sample, which was then ground uniformly and labeled as f-Fe / NC.

[0096] (3) Place f-Fe / NC and sodium hypophosphite in two ceramic boats at a mass ratio of 1:10 and place them in a tube furnace. Place the ceramic boat containing sodium hypophosphite at the upper air vent and the ceramic boat containing f-FeNC at the lower air vent. Under nitrogen protection, incubate at 3℃ for 3 min. -1 A loose and porous iron metal electrocatalyst (f-Fe / NPC) was obtained by heating the temperature to 350℃ and holding it there for two hours.

[0097] Comparative Example 2

[0098] This embodiment provides a method for preparing a loose and porous cobalt metal electrocatalyst (f-Co / NPC), the preparation method comprising the following steps:

[0099] (1) Preparation of nitrogen-doped carbon materials (NC):

[0100] 0.5g of Ketjen Black and 5.0g of melamine were weighed and ground evenly in a clean agate mortar. The mixture was then placed in a porcelain boat and calcined in a tube furnace at 900℃ for 2 hours under a nitrogen atmosphere. The nitrogen-doped carbon material was collected and named NC. The calcination heating rate was 3℃ / min. -1 .

[0101] (2) Disperse 100 mg of NC, 0.5 g of Pluronic F-127, and 1.5 g of melamine in 25 mL of ethanol by ultrasonication for 40 min to obtain dispersion A; dissolve 72 mg of Co(NO3)2·6H2O and 200 mg of o-phenylenediamine in 10 mL of ethanol by ultrasonication for 40 min to obtain solution B. Then, add solution B dropwise to solution A and stir for 2 hours to mix and disperse evenly. Heat the mixed solution system at 70 °C in an oil bath for 6 hours to evaporate to dryness, place it in an oven to dry completely, and then grind it to obtain the cobalt metal bifunctional catalyst precursor. Load the obtained cobalt metal bifunctional catalyst precursor into a ceramic boat and place it in a tube furnace. Under nitrogen protection, heat at 2 °C for 2 min. -1 The heating rate was increased to 350℃ and held for 2 hours, then increased by 2℃ / min. -1 The temperature was increased to 800℃ and held for 2 hours. After complete carbonization, the temperature was reduced to room temperature to obtain the sample, which was then ground uniformly and labeled as f-Co / NC.

[0102] (3) Place f-Co / NC and sodium hypophosphite in two ceramic boats at a mass ratio of 1:10 and place them in a tube furnace. Place the ceramic boat containing sodium hypophosphite at the upper air inlet and the ceramic boat containing f-Co / NC at the lower air inlet. Under nitrogen protection, incubate at 3℃ for 3 min. -1 A loose and porous cobalt metal electrocatalyst (f-Co / NPC) was obtained by heating the temperature to 350℃ and holding it there for two hours.

[0103] The bifunctional electrocatalyst (f-FeCo / NPC) prepared in Example 1, consisting of N and P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres, was used for electrocatalytic oxygen reduction reaction (ORR) and oxygen evolution reaction (OER).

[0104] Electrocatalytic oxygen reduction reaction was tested using a rotating disk electrode (RDE) in a five-cell electrolytic cell with a three-electrode system. 5 mg of the bifunctional electrocatalyst (f-FeCo / NPC) prepared in Example 1, consisting of N,P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres, was mixed with 1 mL of 0.25 wt% Nafion solution (isopropanol solvent) and sonicated to form a homogeneous slurry. 20 μL of this slurry was then dropped onto a 0.197 cm⁻¹ plate. 2 The working electrode is formed on a glassy carbon electrode, the reference electrode is a silver-silver chloride electrode, the counter electrode is a platinum wire, and the electrolyte is an oxygen-saturated 0.1M potassium hydroxide solution (with water as the solvent). Oxygen is continuously introduced during the test, and the rotating disk electrode rotates at 1600 rpm.

[0105] The electrocatalytic oxygen evolution reaction was tested in a five-cell electrolytic cell with a three-electrode system. 5 mg of the bifunctional electrocatalyst (f-FeCo / NPC) prepared in Example 1, consisting of N, P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres, was mixed with 1 mL of 0.5 wt% Nafion solution (isopropanol solvent) and ultrasonically sonicated to form a homogeneous slurry. The slurry was then dropped onto carbon paper (loading amount 0.5 mg / cm³). 2 0.5 mg / cm 2 The catalyst loading (after drying) is clamped onto a platinum electrode to form the working electrode. The reference electrode is a mercury-mercury oxide electrode, the counter electrode is a platinum wire, and the electrolyte is a 1.0M potassium hydroxide solution saturated with oxygen (the solvent is water).

[0106] Assembly and testing of liquid zinc-air batteries: The catalyst ink consisted of 5 mg of the bifunctional electrocatalyst sample of N, P co-doped porous carbon nanosheets supported on FeCo hollow nanospheres obtained in Example 1 of this invention, 80 μL of 5 wt% Nafion solution (solvent: water), 460 μL of deionized water, and 460 μL of anhydrous ethanol. This mixture was uniformly coated onto hydrophobic carbon paper (loading: 0.5 mg / cm³). 2 0.5 mg / cm 2 (The catalyst loading is after drying), and after drying, it is used as a composite cathode. A polished zinc sheet is used as the negative electrode. The electrolyte is a mixed solution of 6.0M potassium hydroxide and 0.2M zinc acetate (with water as the solvent), and a liquid zinc-air battery is assembled. The battery performance was tested at room temperature using an electrochemical workstation (CHI660C).

[0107] like Figure 3 As shown, in 0.1 MkOH solution at a scan rate of 5 mV / s, the ORR polarization curve of the bifunctional electrocatalyst (f-FeCo / NPC) with N and P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres prepared in Example 1 showed a half-wave potential as high as 0.85 V vs RHE, comparable to that of commercial platinum-carbon catalysts, and its limiting current density reached 5.3 mA / cm². The half-wave potential of the f-Fe / NPC bifunctional catalyst prepared in Comparative Example 1 reached 0.86 V vs RHE, which is superior to that of commercial platinum-carbon catalysts. Due to the presence of Fe single atoms, f-FeCo / NPC and f-Fe / NPC form a large number of Fe-NC catalytic active sites, thus exhibiting good ORR catalytic performance. However, the half-wave potential of the f-Co / NPC bifunctional catalyst prepared in Comparative Example 2 is slightly lower than that of the commercial platinum-carbon catalyst, indicating that the ORR activity of Co single atoms is slightly worse than that of Fe single atoms, further demonstrating that the introduction of Fe atoms in this invention is beneficial to the ORR catalytic reaction.

[0108] like Figure 4As shown, the bifunctional electrocatalyst f-FeCo / NPC, consisting of N and P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres, and a commercial Pt / C were tested using a three-electrode system in a 0.1 M oxygen-saturated potassium hydroxide solution. The rotation speed was 400 rpm, and the constant voltage was 0.7 V. The upper curve in the figure represents the bifunctional electrocatalyst f-FeCo / NPC prepared in Example 1. It can be seen that after a stability test lasting 30,000 seconds, the bifunctional electrocatalyst f-FeCo / NPC provided by this invention still maintains 91.6% of its relative current density, while the lower curve for the commercial Pt / C retains only 81.9% of its relative current density. Therefore, the bifunctional electrocatalyst f-FeCo / NPC provided by this invention exhibits better stability.

[0109] like Figure 5 As shown, the it test was performed in 0.1M potassium hydroxide electrolyte under constant potential, and 2 mL of methanol was added after 400 seconds. Figure 5 The upper curve represents a commercial Pt / C catalyst, whose potential changes drastically after the addition of methanol due to poisoning. The lower curve represents the bifunctional electrocatalyst (f-FeCo / NPC) of N, P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres prepared in Example 1. This catalyst showed almost no fluctuation after the addition of methanol, indicating that the bifunctional electrocatalyst (f-FeCo / NPC) of N, P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres prepared in this invention has excellent resistance to methanol poisoning.

[0110] like Figure 6 As shown, linear voltammetric curves of the OER were performed on the bifunctional electrocatalyst f-FeCo / NPC (N,P co-doped porous carbon nanosheets supported on FeCo hollow nanospheres) obtained in Example 1, f-Fe / NPC prepared in Comparative Example 1, f-Co / NPC prepared in Comparative Example 2, and RuO2 / C in a 1.0 M potassium hydroxide electrolyte at a scan rate of 5 mV / s. Figure 6In the OER polarization curves, the bifunctional electrocatalyst (f-FeCo / NPC) of N, P co-doped porous carbon nanosheets supported on FeCo hollow nanospheres, provided by this invention, exhibits an overpotential of only 310 mV at a current density of 10 mA / cm², significantly superior to f-Fe / NPC, f-Co / NPC, and RuO₂ / C. The test results indicate that the FeCo alloy nanoparticles formed by introducing the iron-cobalt bimetallic alloy are highly beneficial for lowering the energy barrier of the OER reaction, thereby enhancing the catalytic activity of OER and reducing the overpotential of the oxygen evolution reaction.

[0111] like Figure 7 As shown, the bifunctional electrocatalyst (f-FeCo / NPC) of N, P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres and the ruthenium oxide / carbon material obtained in Example 1 were subjected to I / O tests in 1.0 M potassium hydroxide electrolyte. The curve above is the test curve of the bifunctional electrocatalyst (f-FeCo / NPC) of N, P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres prepared in Example 1. It can be seen that after a stability test of 12,000 seconds, the bifunctional electrocatalyst of N, P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres provided by the present invention can still maintain a relative current density of 89.1%, which is better than the stability of the ruthenium oxide / carbon material.

[0112] like Figure 8 As shown, Figure 8 (a) is the open-circuit voltage test curve of the liquid zinc-air battery assembled with the bifunctional electrocatalyst (f-FeCo / NPC) of N and P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres obtained in Example 1. It can be seen that the open-circuit voltage of the liquid zinc-air battery is 1.505V, which is higher than that of the liquid zinc-air battery assembled with Pt / C-RuO2 / C. Figure 8 (b) shows the discharge voltage and power density curves of the liquid zinc-air battery assembled from the bifunctional electrocatalyst (f-FeCo / NPC) supported on N and P co-doped porous carbon nanosheets. It can be seen that the highest power density of the liquid zinc-air battery can reach 150.5 mW / cm². -2 The highest power density of the zinc-air battery assembled with Pt / C-RuO2 / C is only 108.3 mW / cm³. -2 Therefore, the liquid zinc-air battery assembled with the bifunctional electrocatalyst (f-FeCo / NPC) of N and P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres obtained in this invention exhibits excellent battery performance and has great application potential.

[0113] Finally, it should be noted that the detailed description of the above embodiments and related drawings is only used to illustrate the technical solutions of the present invention and not to limit them. The present invention is not limited to the specific embodiments described above. Any modifications or equivalent substitutions made by those skilled in the art under the guidance of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a bifunctional electrocatalyst of FeCo hollow nanospheres supported on N and P co-doped porous carbon nanosheets, characterized in that, Includes the following steps: (1) Ketjen black and melamine are ground and mixed, and calcined in a tube furnace to obtain nitrogen-doped carbon material; Ketjen black is a conductive carbon black, the mass ratio of Ketjen black to melamine in step (1) is 1:(10-20), the calcination temperature in step (1) is 800 ℃-900 ℃, the heating rate in step (1) is 2.9-3.1 ℃ / min, the calcination time in step (1) is 2-3 hours, and the protective gas in step (1) is either argon or nitrogen. (2) Pluronic F-127, nitrogen-doped carbon material, and melamine were added to an ethanol solution and ultrasonically dispersed to obtain solution A; ferric nitrate, cobalt nitrate, and o-phenylenediamine were added to an ethanol solution and ultrasonically dissolved to obtain solution B. Solution B was then added dropwise to solution A and mixed and stirred. After the reaction, the mixture was evaporated to dryness and calcined in a tube furnace to obtain f-FeCo / NC precursor powder. The molar ratio of ferric nitrate to cobalt nitrate was (1-2):1, the mass ratio of ferric nitrate to nitrogen-doped carbon material was (1-2):1, the mass ratio of ferric nitrate to the volume of ethanol solution added to solution B was 0.01-0.02 g / mL, the mass ratio of Pluronic F-127 to the volume of ethanol solution added to solution A was 0.01-0.02 g / mL, and the mass ratio of melamine to the volume of ethanol solution added to solution A was 0.050-0.075 g / mL. The mass ratio of o-phenylenediamine to the volume of ethanol solution added to solution B is 0.02-0.04 g / mL; the evaporation temperature is 70℃-90℃; the evaporation time is 3-6 hours; the calcination is divided into two stages: the first stage is to heat to 300℃-350℃ at a heating rate of 1.9-2.1℃ / min and hold for 2-3 hours; the second stage is to heat to 800℃-850℃ at a heating rate of 1.9-2.1℃ / min and hold for 2-3 hours; the protective gas for calcination is either argon or nitrogen. (3) Grind the f-FeCo / NC precursor powder evenly, and calcine and phosphate it in a tube furnace using sodium hypophosphite to obtain a bifunctional electrocatalyst of N and P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres, denoted as f-FeCo / NPC; the mass ratio of f-FeCo / NC precursor to sodium hypophosphite in step (3) is 1:(10-15); the calcination temperature in step (3) is 300 ℃-350 ℃, the heating rate in step (3) is 2.9-3.1 ℃ / min; the calcination time in step (3) is 2-3 hours, and the protective gas in step (3) is either argon or nitrogen.

2. The method for preparing the bifunctional electrocatalyst of N, P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres according to claim 1, characterized in that, The ultrasound time in step (2) is 30-50 min; the stirring time is 2-3 hours.

3. The bifunctional electrocatalyst of N, P co-doped porous carbon nanosheets supported on FeCo hollow nanospheres prepared by the preparation method according to any one of claims 1-2.

4. The application of the bifunctional electrocatalyst of N, P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres as described in claim 3 in electrocatalytic oxygen reduction reaction or electrocatalytic oxygen evolution reaction.

5. The application according to claim 4, characterized in that, Application of the bifunctional electrocatalyst of N,P co-doped porous carbon nanosheets supporting FeCo hollow nanospheres in the preparation of zinc-air battery cathode materials.

Images