Preparation and application of multifunctional composite nanohollow spheres
By constructing a multi-component composite catalyst of Ag/CoFe/Co2P/NC, the problems of high cost and slow kinetics of precious metal catalysts were solved, and efficient catalysis of HER, OER and ORR reactions was achieved. It has excellent electrocatalytic activity and stability and is suitable for water electrolysis and zinc-air batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NORTHWEST NORMAL UNIVERSITY
- Filing Date
- 2023-05-23
- Publication Date
- 2026-07-24
Smart Images
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Abstract
Description
Technical Field
[0001] This invention relates to a method for preparing multifunctional composite hollow nanospheres, which are mainly used for electrocatalytic hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), water electrolysis reaction, and zinc-air battery in alkaline media. Background Technology
[0002] In recent years, with the rapid depletion of fossil fuels and the emergence of various environmental problems, it has become necessary to develop various clean energy sources and electrical energy storage and conversion technologies. Water electrolysis for hydrogen production and metal-air batteries are considered promising hydrogen harvesting and electrochemical energy storage technologies due to their environmental friendliness, high energy density, high safety, and low cost. The hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) are the electrochemical reactions involved in these two technologies. However, the slow kinetics of these reactions severely affect their final performance. Furthermore, commercially available noble metal catalysts such as Pt, Ir-based, and RuO2 remain the main catalysts for HER, ORR, and OER. However, these noble metal catalysts are expensive and scarce, making them unsuitable for large-scale applications. Therefore, developing cost-effective and highly active electrocatalysts for HER, OER, and ORR catalysis is particularly important.
[0003] In recent years, the development of inexpensive and efficient non-precious metal catalysts has become a research hotspot. These catalysts primarily consist of transition metal carbides, nitrides, oxides, hydroxides, phosphides, sulfides, selenides, alloys, and their composites. Transition metal alloy-based catalysts have consistently been a research focus because alloying can alter the electronic structure and geometry of the catalyst. Transition metal phosphides have attracted widespread attention due to their low cost, abundant resources, high stability, unique physical properties, and tunable multifunctionality. However, their poor conductivity and excessively strong adsorption energy of intermediates limit their effectiveness. In summary, this invention constructs an Ag / CoFe / Co2P / NC multi-component composite catalyst by loading highly conductive silver nanoparticles. Utilizing the synergistic effect of these multiple components, a multifunctional, highly active electrocatalyst capable of simultaneously catalyzing HER, OER, and ORR is obtained. Summary of the Invention
[0004] The purpose of this invention is to provide a simple, effective, and controllable method for preparing Ag / CoFe / Co2P / NC trifunctional composite catalysts with hollow sphere structures, and to test the performance of the prepared composite catalysts in catalyzing HER, OER, ORR, water electrolysis, and zinc-air batteries.
[0005] I. Preparation of Multifunctional Composite Hollow Nanospheres The preparation of the multifunctional composite hollow nanospheres of the present invention includes the following process steps: (1) Preparation of precursor: Dissolve ferricyanide in water to form solution A, dissolve cobalt salt, silver salt and sodium citrate in water to form solution B, add solution B to solution A, stir for 10-30 min, age for 24-48 h, centrifuge, wash thoroughly with distilled water and freeze dry to obtain the precursor.
[0006] The cobalt salt is one of Co(CH3COO)2·4H2O, CoCl2·6H2O, and Co(NO3)2·6H2O; the ferricyanide is one of K3[Fe(CN)6], Na3[Fe(CN)6], K4[Fe(CN)6], and Na4[Fe(CN)6]; the silver salt is one of AgNO3 and AgCl; the molar ratio of ferricyanide to cobalt salt is 1:2-1:6; and the mass ratio of silver salt to (cobalt salt + ferricyanide) is 1:5-1:15.
[0007] (2) Preparation of multifunctional composite hollow nanospheres: The precursor prepared above was first heat-treated in a tube furnace at 600-900℃ (preferably 800℃) for 2-5 hours under N2 atmosphere to obtain pyrolysis products, with a heating rate of 1-3℃ / min (preferably 2℃ / min); then, using sodium hypophosphite as the phosphorus source, it was placed in a tube furnace and phosphating was continued at 200-400℃ (preferably 300℃) for 1-5 hours (preferably 3 hours) to obtain the final composite hollow spheres. The mass ratio of the pyrolysis products to sodium hypophosphite was 1:5-1:20.
[0008] The prepared composite material consists of hollow nanospheres with a diameter of approximately 100 nm and a wall thickness of 15-25 nm. It is composed of four components: elemental Ag nanoparticles, cobalt-iron alloy (CoFe), metal phosphide (Co2P), and nitrogen-doped carbon material (NC). The Ag content is 1.5-2.5%, the CoFe content is 31.5-50.0%, the Co2P content is 18.4-37.5%, and the NC content is 32.1%-43.6%. The pore size of the composite hollow nanospheres is mainly concentrated in the mesoporous range of 3-6 nm. The specific surface area of the composite material is 31-55 m². 2 / g, pore volume 0.05-0.10 cm³ 3 / g.
[0009] II. Structure of Multifunctional Composite Hollow Nanospheres Figure 1 This is a TEM image of the catalyst prepared in Example 1 of the present invention. As can be seen from the image, the prepared catalyst is a porous hollow sphere with a diameter of approximately 100 nm.
[0010] Figure 2The following are XRD patterns of the catalysts prepared in Examples 1-3 of this invention: (a) Example 1; (b) Example 2; (c) Example 3. As shown in the figures, all three catalysts were composed of four components: Ag, CoFe, Co2P, and NC. Diffraction peaks of the Ag (111), (200), (220), (311), and (222) crystal planes appeared at 2θ values of 38.1°, 44.3°, 64.4°, 77.4°, and 81.5°, respectively (JCPDS NO.04-0783). Diffraction peaks at 2θ values of 44.8°, 63.3°, and 82.7° were attributed to the CoFe (110), (200), and (211) crystal planes, respectively (JCPDS NO.49-1568). The diffraction peak at 2θ = 40.7° corresponds to the Co2P(121) crystal plane (JCPDS No. 32-0306). No carbon peak was observed in the XRD, possibly because the peaks of the CoFe alloy were too strong, masking the appearance of the C peak.
[0011] Figure 3 This is the N2 adsorption-desorption isotherm of the catalyst prepared in Example 1 of this invention. The isotherm shows that the obtained sample exhibits a type IV isotherm and an H3 hysteresis loop, indicating that the sample has a multi-level porous structure.
[0012] Figure 4 This is a pore size distribution diagram of the catalyst prepared in Example 1 of this invention. As shown in the diagram, the pore size distribution of the obtained sample is mainly concentrated in the mesoporous range of 3-6 nm, which further proves that the catalyst has abundant mesopores. The specific surface area of this sample is 55 m² / g, and the pore volume is 0.10 cm³. 3 / g.
[0013] III. Performance of Multifunctional Composite Hollow Nanospheres Electrocatalytic hydrogen evolution, oxygen evolution, and oxygen reduction performance testing: A certain amount of the composite material was ultrasonically dispersed in ethanol, and an appropriate amount of 5% Nafion solution was added and mixed evenly to prepare a suspension. A certain amount of this suspension was drop-coated onto a glassy carbon electrode and allowed to air dry to prepare a working electrode for electrocatalytic hydrogen evolution, oxygen evolution, and oxygen reduction. The test was conducted using a three-electrode system on a CHI760E electrochemical workstation.
[0014] Electrolysis performance test: A certain amount of the above suspension was drop-coated onto acid-treated nickel foam to prepare a working electrode for electrocatalytic water splitting. The test was conducted using a two-electrode system on a CHI760E electrochemical workstation.
[0015] Zinc-air cell test: A certain amount of the above suspension was coated onto a 1.0 cm layer. 2The zinc-air battery was used as an air cathode on hydrophobic carbon paper and as an anode on a 2 mm thick zinc plate (the zinc plate was sanded and rinsed with distilled water to remove the oxide film on its surface). The performance of the zinc-air battery was tested using a CHI 760E electrochemical workstation and a LANHE CT2001A battery tester (Wuhan, China). The electrolyte was 6.0 M KOH and 0.2 M Zn(CH3OO)2.
[0016] Figure 5 This is the LSV curve of the catalyst prepared in Example 1 of this invention catalyzing HER in 1 M KOH. As shown in the figure, the obtained catalyst achieves a current density of 10 mA / cm² when catalyzing HER in 1.0 M KOH. 2 The overpotential was 200 mV, which proves that the catalyst has excellent catalytic activity for HER.
[0017] Figure 6 This is the LSV curve of the catalyst prepared in Example 1 of this invention catalyzing OER in 1 M KOH. As shown in the figure, the obtained catalyst achieves a current density of 10 mA / cm² when catalyzing OER in 1.0 M KOH. 2 The overpotential was 293 mV, which proves that the catalyst has excellent catalytic activity for OER.
[0018] Figure 7 The figure shows the LSV curve of the catalyst prepared in Example 1 of this invention for ORR catalysis in 0.1 M KOH. As can be seen from the figure, the obtained catalyst has an electrical half-wave potential of 759 mV when catalyzing ORR in 0.1 M KOH, which proves that the catalyst has excellent catalytic activity for ORR.
[0019] Figure 8 This is the LSV curve of the catalyst prepared in Example 1 of this invention for catalytic water electrolysis in 1 M KOH. As shown in the figure, the obtained catalyst achieves a current density of 10 mA / cm² when catalyzing the total decomposition of water in 1.0 M KOH. 2 The decomposition voltage was 1.56 V, proving that the catalyst, as a bifunctional catalyst for HER and OER, has excellent catalytic activity for water electrolysis.
[0020] Figure 9 This is the relative current density-time curve of the catalyst prepared in Example 1 of this invention during the catalytic electrolysis of water in 1 M KOH. As can be seen from the figure, the current density of the obtained catalyst remained almost unchanged after 20 h of stability testing, proving that the catalyst has strong stability in the catalytic electrolysis of water.
[0021] Figure 10This figure shows the charge-discharge cycle curves of a zinc-air battery assembled with the catalyst prepared in Example 1 of this invention as an air cathode in 6.0 M KOH and 0.2 M zinc acetate. As can be seen from the figure, the obtained catalyst can achieve a charge-discharge cycle at a constant current density of 10 mAcm⁻¹. -2 After 200 charge-discharge cycles (1 cycle: 5 min discharge, 5 min charge), the voltage of the zinc-air battery did not decrease significantly. Furthermore, at the 50th cycle, its charging voltage was 1.965 V, the discharging voltage was 1.173 V, and the voltage gap was only 0.792 V, which also indicates that the catalyst has good cycling performance as an air cathode.
[0022] Figure 11 This image shows two zinc-air batteries connected in series, assembled using the catalyst prepared in Example 1 of this invention as an air cathode in 6.0 M KOH and 0.2 M zinc acetate, to produce an LED. As shown in the image, the device can light a yellow-green LED (2.2V), indicating that the catalyst has certain application prospects.
[0023] In summary, the test results show that the catalyst in 1.0 M KOH solution at 10 mA / cm 2 At the given current density, the overpotential of HER can be as low as 200mV, the overpotential of OER can be as low as 293mV, the half-wave potential of ORR is 759mV, and the decomposition voltage of water electrolysis can be as low as 1.56 V. It has good stability in water electrolysis and has good cycle performance and application performance as an air cathode of zinc-air battery.
[0024] Compared with the prior art, the present invention has the following advantages: 1. Effective in-situ composite of Ag, CoFe, Co2P and nitrogen-doped carbon materials can form effective synergistic effects and heterogeneous interfaces between different components, endowing the catalyst with excellent intrinsic catalytic activity and superior interfacial charge transport rate, thus accelerating electrocatalytic reactions.
[0025] 2. Combining Ag with nitrogen-doped carbon materials can reduce the aggregation of silver nanoparticles, enhance electron transport, increase the conductivity of the catalyst, and thus improve its electrocatalytic activity.
[0026] 3. Hollow and porous structures not only accelerate electrolyte permeation but also provide more channels for rapid mass transfer during the reaction, which is beneficial for improving catalytic performance.
[0027] 4. Activity tests show that the composite material prepared in this invention has excellent electrocatalytic activity for hydrogen evolution, oxygen evolution, oxygen reduction reactions, water electrolysis, and zinc-air batteries. It also has good stability in alkaline media and promising application prospects. Attached Figure Description
[0028] Figure 1 This is a TEM image of the catalyst prepared in Example 1 of the present invention.
[0029] Figure 2 Here are the XRD patterns of the catalysts prepared in Examples 1-3 of this invention: (a) Example 1; (b) Example 2; (c) Example 3.
[0030] Figure 3 This is the N2 adsorption-desorption isotherm of the catalyst prepared in Example 1 of this invention.
[0031] Figure 4 This is a pore size distribution diagram of the catalyst prepared in Example 1 of the present invention.
[0032] Figure 5 This is the LSV curve of the catalyst prepared in Example 1 of the present invention catalyzing HER in 1 M KOH.
[0033] Figure 6 This is the LSV curve of the catalyst prepared in Example 1 of this invention catalyzing OER in 1 M KOH.
[0034] Figure 7 This is the LSV curve of ORR catalyzed by the catalyst prepared in Example 1 of this invention in 0.1 M KOH.
[0035] Figure 8 This is the LSV curve of the catalyst prepared in Example 1 of this invention for catalytic electrolysis of water in 1 M KOH.
[0036] Figure 9 This is the relative current density-time curve of the catalyst prepared in Example 1 of this invention for catalytic electrolysis of water in 1 M KOH.
[0037] Figure 10 This is the charge-discharge cycle curve of a zinc-air battery assembled with the catalyst prepared in Example 1 of this invention as an air cathode in 6.0 M KOH and 0.2 M zinc acetate.
[0038] Figure 11 The image shows two zinc-air batteries assembled in series with the catalyst prepared in Example 1 of this invention as air cathodes in 6.0 M KOH and 0.2 M zinc acetate, lighting an LED. Detailed Implementation
[0039] The multifunctional composite hollow nanospheres of the present invention will be described in more detail below through specific embodiments.
[0040] Example 1 (1) Preparation of precursor: 0.748 g Co(Ac)2·4H2O and 0.662 g C6H4Na3O7·2H2O were dissolved in 10 mL of deionized water and labeled as solution A; 0.330 g K3[Fe(CN)6] was dissolved in 10 mL of deionized water and labeled as solution B; solution A was slowly added to solution B, and after precipitate was formed, 0.108 g / 5 mL AgNO3 solution was slowly added dropwise. The mixture was stirred at room temperature for 30 min and then aged for 24 h. The solid product was washed several times by centrifugation with distilled water and then freeze-dried to obtain the precursor. The molar ratio of K3[Fe(CN)6] to Co(Ac)2·4H2O was 1:3; the mass ratio of AgNO3 to (Co(Ac)2·4H2O + K3[Fe(CN)6]) was 1:10.
[0041] (2) Preparation of multifunctional composite hollow nanospheres: The precursor prepared above was placed in a tube furnace and heated to 2℃ for 1 minute. -1 The temperature was increased to 800 °C and held for 2 h for heat treatment, and then further phosphating was performed in N2 using NaH2PO2·H2O as the phosphorus source at 2 °C / min. -1 The temperature was increased to 300 °C and held for 3 h. The amount of NaH2PO2·H2O used was 10 times the mass of the pyrolysis product.
[0042] The prepared composite material consists of hollow nanospheres with a diameter of approximately 100 nm and a wall thickness of 15-25 nm. It is composed of four components: elemental Ag nanoparticles, cobalt-iron alloy (CoFe), metal phosphide (Co2P), and nitrogen-doped carbon material (NC). The Ag content is 2.0%, CoFe is 37.5%, Co2P is 22.6%, and NC is 37.9%. The pore size of the composite hollow nanospheres is mainly concentrated in the mesoporous range of 3-6 nm. The specific surface area of the composite material is 55 m² / g, and the pore volume is 0.10 cm³. 3 / g.
[0043] (3) Catalytic performance test Test Method: Weigh 5.0 mg of the prepared catalyst and add it to a solution of 0.5 mL anhydrous ethanol and 10 μL Nafion (Dupont, 5 wt%). Sonicate the solution for 30 min, and then take 5 μL of the suspension and coat it onto a 3 mm glassy carbon electrode. The glassy carbon electrode was used as the working electrode, the graphite electrode as the counter electrode, and the Ag / AgCl electrode as the reference electrode in a three-electrode system. The electrolyte solution used for HER and OER testing was 1.0 M KOH, and the electrolyte solution used for ORR testing was 0.1 M KOH. For water electrolysis performance testing, a two-electrode system was used, with the prepared suspension being dropped onto two 1 cm electrodes. 2On the nickel foam, the catalyst loading was 1 mg / cm³. 2 The cathode and anode were fabricated and tested in a 1.0 M KOH solution. Stability testing was performed at a current density of 10 mA / cm². 2 The method involves testing the current-time curve at the corresponding potential. The zinc-air cell test involves coating a certain amount of the above suspension onto a 1.0 cm² plate. 2 The zinc-air battery was used as an air cathode on hydrophobic carbon paper and as an anode on a 2 mm thick zinc plate (the zinc plate was sanded and rinsed with distilled water to remove the oxide film on its surface). The performance of the zinc-air battery was tested using a CHI 760E electrochemical workstation and a LANHE CT2001A battery tester (Wuhan, China). The electrolyte was 6.0 M KOH and 0.2 M Zn(CH3OO)2.
[0044] Test results: at a current density of 10 mA / cm² 2 At that time, the overpotential for catalytic HER was 200 mV ( Figure 5 The overpotential for catalytic OER is 293 mV. Figure 6 The catalytic ORR half-wave potential is 759 mV. Figure 7 The decomposition voltage of catalytic water electrolysis is 1.56 V (10 mA / cm). 2 hour)( Figure 8 The catalyst's current density remained almost unchanged after a 10-hour stability test. Figure 9 The constant current density is 10 mAcm. -2 After 200 charge-discharge cycles (1 cycle: 5 min discharge, 5 min charge), the voltage of the zinc-air battery did not decrease significantly. Figure 10 ), can light up a yellow-green LED light ( Figure 11 These results demonstrate that the catalyst exhibits excellent electrocatalytic activity in hydrogen evolution, oxygen evolution, oxygen reduction, water electrolysis, and zinc-air batteries, and shows good stability and application prospects in alkaline media.
[0045] Example 2 (1) Preparation of precursor: 0.996 g Co(Ac)2·4H2O and 0.662 g C6H4Na3O7·2H2O were dissolved in 10 mL of deionized water and labeled as solution A; 0.330 g K3[Fe(CN)6] was dissolved in 10 mL of deionized water and labeled as solution B. Solution A was then slowly added to solution B. After a precipitate was formed, 0.133 g / 5 mL AgNO3 solution was slowly added dropwise. After stirring for 30 min, the mixture was aged for 24 h. The solid product was washed several times by centrifugation with distilled water and then freeze-dried to obtain the precursor. The molar ratio of K3[Fe(CN)6] to Co(Ac)2·4H2O was 1:4; the mass ratio of AgNO3 to (Co(Ac)2·4H2O + K3[Fe(CN)6]) was 1:10.
[0046] (2) Preparation of hollow sphere multi-component composite material: The precursor prepared above was placed in a tube furnace and heated to 5℃ for 1 minute. -1 The temperature was increased to 800 °C and held for 2 h for heat treatment, followed by further phosphating in N2 using NaH2PO2·H2O as the phosphorus source at 2 °C / min. -1 The temperature was increased to 300 °C and held for 3 h. The amount of NaH2PO2·H2O used was 10 times the mass of the pyrolysis product.
[0047] The prepared composite material consists of hollow nanospheres with a diameter of approximately 100 nm and a wall thickness of 15-25 nm. It is composed of four components: elemental Ag nanoparticles, cobalt-iron alloy (CoFe), metal phosphide (Co2P), and nitrogen-doped carbon material (NC). The Ag content is 1.7%, CoFe is 39.1%, Co2P is 25.2%, and NC is 34.0%. The pore size of the composite hollow nanospheres is mainly concentrated in the mesoporous range of 3-6 nm. The specific surface area of the composite material is 50 m² / g, and the pore volume is 0.08 cm³. 3 / g.
[0048] (3) Catalytic performance test Test method: Same as Example 1; Test results: at a current density of 10 mA / cm² 2 At that time, the overpotential for catalytic HER was 223 mV, the overpotential for catalytic OER was 313 mV, and the half-wave potential for catalytic ORR was 630 mV. The decomposition voltage for catalytic water electrolysis was 1.62 V (10 mA / cm²). 2 hour).
[0049] Example 3 (1) Preparation of precursor: 0.748 g Co(Ac)2·4H2O and 0.662 g C6H4Na3O7·2H2O were dissolved in 10 mL of deionized water and labeled as solution A; 0.330 g K3[Fe(CN)6] was dissolved in 10 mL of deionized water and labeled as solution B; solution A was slowly added to solution B, and after precipitate was formed, 0.108 g / 5 mL AgNO3 solution was slowly added dropwise, stirred for 30 min, and then aged for 24 h. The solid product was washed several times by centrifugation with distilled water and then freeze-dried to obtain the precursor. The molar ratio of K3[Fe(CN)6] to Co(Ac)2·4H2O was 1:3; the mass ratio of AgNO3 to (Co(Ac)2·4H2O + K3[Fe(CN)6]) was 1:10.
[0050] (2) Preparation of multifunctional composite hollow nanospheres: The precursor prepared above was placed in a tube furnace and heated to 2 °C for 1 minute. -1 The temperature was increased to 800 °C and held for 2 h for heat treatment, followed by further phosphating in N2 using NaH2PO2·H2O as the phosphorus source at 2 °C / min. -1 The temperature was increased to 300 °C and held for 3 h. The amount of NaH2PO2·H2O used was 15 times the mass of the pyrolysis products.
[0051] The prepared composite material consists of hollow nanospheres with a diameter of approximately 100 nm and a wall thickness of 15-25 nm. It is composed of four components: elemental Ag nanoparticles, cobalt-iron alloy (CoFe), metal phosphide (Co2P), and nitrogen-doped carbon material (NC). The Ag content is 2.2%, CoFe is 32.1%, Co2P is 32.6%, and NC is 33.1%. The pore size of the composite hollow nanospheres is mainly concentrated in the mesoporous range of 3-6 nm. The specific surface area of the composite material is 48 m² / g, and the pore volume is 0.065 cm³. 3 / g.
[0052] (3) Catalytic performance test Test method: Same as Example 1; Test results: at a current density of 10 mA / cm² 2 At that time, the overpotential for catalytic HER was 237 mV, the overpotential for catalytic OER was 327 mV, and the half-wave potential for catalytic ORR was 668 mV. The decomposition voltage for catalytic water electrolysis was 1.65 V (10 mA / cm²). 2 hour).
Claims
1. A method for preparing multifunctional composite hollow nanospheres, comprising the following process steps: (1) Preparation of precursor: Dissolve cobalt salt and sodium citrate in water to form solution A, dissolve ferricyanide in water to form solution B, add solution A to solution B, and after a precipitate is formed, add silver salt solution, stir at room temperature for 10-30 min, age for 24-48 h, centrifuge, wash thoroughly with distilled water and freeze dry to obtain the precursor; the molar ratio of ferricyanide to cobalt salt is 1:2-1:6; the mass ratio of silver salt to the total mass of cobalt salt and ferricyanide is 1:5-1:15; (2) Preparation of composite hollow nanospheres: The precursor prepared above is first heat-treated in a tube furnace at 600-900℃ for 2-5h under N2 atmosphere, with a heating rate of 1-3℃ / min; then, using sodium hypophosphite as phosphorus source, it is phosphating at 200-400℃ for 1-5h to obtain the final multifunctional composite hollow nanosphere catalyst.
2. The method for preparing multifunctional composite hollow nanospheres as described in claim 1, characterized in that: In step (1), the cobalt salt is one of Co(CH3COO)2·4H2O, CoCl2·6H2O, or Co(NO3)2·6H2O.
3. The method for preparing multifunctional composite hollow nanospheres as described in claim 1, characterized in that: In step (1), the ferricyanide is one of K3[Fe(CN)6], Na3[Fe(CN)6], K4[Fe(CN)6], and Na4[Fe(CN)6].
4. The method for preparing multifunctional composite hollow nanospheres as described in claim 1, characterized in that: In step (1), the silver salt is either AgNO3 or AgCl.
5. The method for preparing multifunctional composite hollow nanospheres as described in claim 1, characterized in that: The prepared composite material consists of hollow nanospheres with a diameter of approximately 100 nm and a wall thickness of 15-25 nm. It is composed of four components: elemental Ag nanoparticles, cobalt-iron alloy (CoFe), metal phosphide (Co2P), and nitrogen-doped carbon materials. The Ag content is 1.5-2.5%, CoFe content is 31.5-50.0%, Co2P content is 18.4-37.5%, and NC content is 32.1%-43.6%. The pore size of the composite hollow nanospheres is mainly concentrated in the mesoporous range of 3-6 nm. The specific surface area of the composite material is 31-55 m². 2 / g, pore volume 0.05-0.10cm³ 3 / g.
6. The application of the multifunctional composite hollow nanospheres prepared by the method described in claim 1 in the electrocatalytic hydrogen evolution reaction.
7. The application of the multifunctional composite hollow nanospheres prepared by the method described in claim 1 in the electrocatalytic oxygen evolution reaction.
8. The application of the multifunctional composite hollow nanospheres prepared by the method described in claim 1 in the electrocatalytic oxygen reduction reaction.
9. The application of the multifunctional composite hollow nanospheres prepared by the method described in claim 1 in the electrocatalytic water splitting reaction.
10. The application of the multifunctional composite hollow nanospheres prepared by the method described in claim 1 in zinc-air batteries.