阅读说明：本技术 三维氮掺杂碳基材料负载双金属磷化物双功能催化剂及其制备方法和应用 (Three-dimensional nitrogen-doped carbon-based material loaded bimetallic phosphide bifunctional catalyst and preparation method and application thereof ) 是由 韦萍洁 赵叶民 于国强 廖丽梅 徐超 周鑫佑 钟诚兵 尹王晨 何卓霖 杨超 刘劲 于 2019-05-07 设计创作，主要内容包括：本发明提供了一种三维氮掺杂碳基材料负载双金属磷化物双功能催化剂及其制备方法和应用。该催化剂是由双过渡金属磷化物与氮掺杂的碳纳米管组成的复合材料。先将三聚氰胺与碳纳米管以一定质量比混合热处理,制备三维氮掺杂碳材料；再向三维氮掺杂碳材料的水溶液中混入一定比例的双过渡金属硝酸盐,并将此混合物在惰性电极表面干燥；然后在中性缓冲溶液中电沉积0.5-1.5分钟,清洗、干燥；最后与亚磷酸二氢钠在350℃氮气氛围下反应2小时,即得到本发明所述催化剂。该催化剂在碱性条件下具有优异的催化析氧性能(OER),也具有高效的催化氧还原功能(ORR),且所用原料价格低廉,工艺简单,反应时间短,适合批量生产。(The invention provides a three-dimensional nitrogen-doped carbon-based material loaded bi-metal phosphide bifunctional catalyst and a preparation method and application thereof. The catalyst is a composite material consisting of double transition metal phosphide and nitrogen-doped carbon nanotubes. Firstly, mixing melamine and carbon nano tubes according to a certain mass ratio for heat treatment to prepare a three-dimensional nitrogen-doped carbon material; then mixing a certain proportion of double transition metal nitrate into the aqueous solution of the three-dimensional nitrogen-doped carbon material, and drying the mixture on the surface of an inert electrode; then electrodepositing for 0.5-1.5 minutes in neutral buffer solution, cleaning and drying; and finally reacting with sodium dihydrogen phosphite for 2 hours at 350 ℃ in a nitrogen atmosphere to obtain the catalyst. The catalyst has excellent catalytic oxygen evolution performance (OER) under alkaline conditions, also has efficient catalytic oxygen reduction function (ORR), and is low in price of raw materials, simple in process, short in reaction time and suitable for batch production.)

1. A three-dimensional nitrogen-doped carbon-based material loaded bi-metal phosphide bifunctional catalyst is characterized in that: the catalyst is a composite material consisting of a three-dimensional nitrogen-doped carbon-based material and a bimetallic phosphide.

2. A method for preparing the three-dimensional nitrogen-doped carbon-based material supported bimetallic phosphide bifunctional catalyst as claimed in claim 1, wherein the method comprises the following steps:

the method comprises the following steps:

(1) weighing melamine and carbon nano tubes according to the mass ratio of 1.5:1, performing ultrasonic dispersion in a solvent uniformly, drying, and performing heat treatment at 550 ℃ for 2 hours to obtain a three-dimensional nitrogen-doped carbon-based material;

(2) ultrasonically stirring the three-dimensional nitrogen-doped carbon-based material and divalent metal ions uniformly by using an organic solution with the mass molar ratio of 1g to 0.3-0.6mol, and drying on the surface of an inert electrode;

(3) placing the inert electrode of the load material in a negative electrode in a neutral phosphoric acid buffer solution, electrolyzing for 0.5-1.5 minutes under the current of-10 mA, washing and drying to obtain a precursor;

(4) and (3) reacting the precursor with sodium dihydrogen phosphite at 350 ℃ for 2 hours in a nitrogen atmosphere, and cooling to obtain the three-dimensional nitrogen-doped carbon-based material loaded bi-metal phosphide bi-functional composite catalyst.

3. The method for preparing the three-dimensional nitrogen-doped carbon-based material supported bimetallic phosphide bifunctional catalyst as claimed in claim 2, wherein the method comprises the following steps: in the step (2), the divalent metal ions include Ni²⁺，Fe²⁺，Co²⁺，Mn²⁺，Cu²⁺Either one or both of them.

4. The method for preparing the three-dimensional nitrogen-doped carbon-based material supported bimetallic phosphide bifunctional catalyst as claimed in claim 3, wherein the method comprises the following steps: in the step (3), the inert electrode is any one of conductive glass, a glassy carbon electrode and a platinum electrode.

5. The method for preparing the three-dimensional nitrogen-doped carbon-based material supported bimetallic phosphide bifunctional catalyst as claimed in claim 4, wherein the method comprises the following steps: the three-dimensional nitrogen-doped carbon-based material is a composition of melamine and carbon nanotubes, and the specific surface area reaches 150m 2/g.

6. The method for preparing the three-dimensional nitrogen-doped carbon-based material supported bimetallic phosphide bifunctional catalyst as claimed in claim 5, wherein the method comprises the following steps: the bimetallic phosphide is nano-particles with the diameter of 5-20 nm.

7. The method of any one of claims 2-6, wherein the three-dimensional nitrogen-doped carbon-based material supported bi-metal phosphide bi-functional catalyst is prepared by: the specific surface area of the three-dimensional nitrogen-doped carbon-based material loaded double-metal phosphide double-function composite catalyst reaches 420m²/g。

8. The method for preparing the three-dimensional nitrogen-doped carbon-based material supported bimetallic phosphide bifunctional catalyst as claimed in claim 2, wherein the method comprises the following steps: in the step (3), the precursors of the transition metal phosphide are sodium dihydrogen phosphite and any two of nickel acetate, iron acetate, cobalt acetate, manganese acetate and copper acetate.

9. The method for preparing the three-dimensional nitrogen-doped carbon-based material supported bimetallic phosphide bifunctional catalyst as claimed in claim 8, wherein the method comprises the following steps: the preparation method of the precursor of the transition metal phosphide can be divided into two steps:

1) loading a transition metal: loading transition metal elements by using an in-situ electrochemical reduction method;

2) phosphorization of transition metal: the phosphating of the transition metal was carried out with sodium dihydrogen phosphite at 350 ℃ under nitrogen.

10. Use of the bi-metal phosphide-supported bifunctional catalyst as claimed in claim 9, wherein: the three-dimensional nitrogen-doped carbon-based material has a typical spatial configuration of uniform cross support of a graphene sheet layer and a nanotube, wherein the size of the nitrogen-doped graphene sheet layer is nano-scale and is 100-300 nm; the diameter of the nitrogen-doped carbon nanotube is 8-15nm, the length of the nitrogen-doped carbon nanotube is 100nm-1 mu m, the material has a larger specific surface area, and also has good conductivity and a large number of three-dimensional space structures, and the doping of nitrogen element in the material provides more active sites, the three-dimensional nitrogen-doped carbon-based material is beneficial to the effective load of transition metal, and is beneficial to enhancing the ORR and OER catalytic performance of the composite catalyst, the double-transition metal phosphide has the synergistic effect of metal and phosphorus, and the catalytic performance of the double-transition metal phosphide is improved in a controllable manner by adjusting the metal type.

Technical Field

The invention belongs to the technical field of new energy such as fuel cells, water splitting desorption oxygen and the like, and particularly relates to a three-dimensional nitrogen-doped carbon-based material loaded bi-metal phosphide dual-function catalyst, and a preparation method and application thereof.

Background

Energy is a material basis on which human society relies on survival and development. At present, about 85 percent of the global energy consumption is caused by the combustion of fossil fuel, and the combustion of the fossil fuel causes CO in the atmosphere₂Concentrations continue to rise cumulatively and eventually contribute to the greenhouse effect and global warming. Therefore, efficient and low-cost clean energy is actively researched and developed in various countries around the world. New energy technologies such as fuel cells (especially proton exchange membrane fuel cells), water splitting devices and metal-air batteries are important directions for research at present [ chem.Rev.2015,115,9869-9921]. Conventional noble metals (Pt, Ir,Ru, etc.) and alloys thereof have good catalytic activities for oxygen reduction (ORR) and Oxygen Evolution (OER), but are expensive and susceptible to poisoning and deactivation, which severely restricts the development of these energy technologies. Therefore, the non-noble metal double-effect catalyst with high efficiency, stability and low price becomes a research and development hotspot of new energy technology.

Transition metal (such as cobalt, nickel, iron and manganese) oxides have the advantages of low price, abundant reserves and the like, can form various crystal configurations, and are considered by many scientists to be catalytic materials capable of replacing noble metals. The Schuhmann group studied a series of perovskite-type transition metal oxides, which have good ORR and OER catalytic performances, but still need to be doped with a small amount of rare earth elements (La, Ce, etc.) [ Chemhyschem 2014,15,2810-2816 ]; a series of transition metal hydroxides prepared by Nocera et al, in which different crystalline structures were found to have a large influence on ORR and OER catalytic performance [ j.am.chem.soc.2012,134,6801-6809 ]. Although these materials have a certain catalytic potential, the synthesis process is complex, the preparation time is long, and the performance is still insufficient to meet the requirements of industrial production.

In summary, in order to solve the above technical problems in the prior art, the present invention provides a bi-metal phosphide bifunctional catalyst loaded on a three-dimensional nitrogen-doped carbon-based material, and a preparation method and an application thereof. The double transition metal phosphide has the synergistic effect of metal and phosphorus, and the catalytic performance of the double transition metal phosphide can be improved in a controllable manner by adjusting the metal species. The three-dimensional nitrogen-doped carbon-based material prepared by the invention is assisted in the double-transition metal phosphide bifunctional composite catalyst in the prior art. Therefore, the implementation method of the invention can controllably prepare the three-dimensional nitrogen-doped carbon-based material and assist the double-transition metal phosphide double-function composite catalyst, and has important significance for widening the research direction of the double-function catalyst.

Disclosure of Invention

The invention provides a three-dimensional nitrogen-doped carbon-based material loaded bimetallic phosphide bifunctional catalyst, a preparation method and application thereof, and provides an ORR and OER bifunctional composite catalyst with short preparation time, simple process, controllable reaction and high activity and a preparation method thereof, wherein the specific technical scheme is as follows:

a bi-metal phosphide bi-functional catalyst loaded on a three-dimensional nitrogen-doped carbon-based material is a composite material consisting of the three-dimensional nitrogen-doped carbon-based material and bi-metal phosphide.

The preparation method of the three-dimensional nitrogen-doped carbon-based material loaded bimetallic phosphide bifunctional catalyst comprises the following steps:

the method comprises the following steps:

(1) weighing melamine and carbon nano tubes according to the mass ratio of 1.5:1, performing ultrasonic dispersion in a solvent uniformly, drying, and performing heat treatment at 550 ℃ for 2 hours to obtain a three-dimensional nitrogen-doped carbon-based material;

(2) ultrasonically stirring the three-dimensional nitrogen-doped carbon-based material and divalent metal ions uniformly by using an organic solution with the mass molar ratio of 1g to 0.3-0.6mol, and drying on the surface of an inert electrode;

(3) and placing the inert electrode of the load material in a negative electrode in a neutral phosphoric acid buffer solution, electrolyzing for 0.5-1.5 minutes under the current of-10 mA, washing and drying to obtain the precursor.

(4) And (3) reacting the precursor with sodium dihydrogen phosphite at 350 ℃ for 2 hours in a nitrogen atmosphere, and cooling to obtain the three-dimensional nitrogen-doped carbon-based material loaded bi-metal phosphide bi-functional composite catalyst.

The preparation method of the three-dimensional nitrogen-doped carbon-based material loaded bimetallic phosphide bifunctional catalyst comprises the following steps: in the step (2), the divalent metal ions include Ni²⁺，Fe²⁺，Co²⁺，Mn²⁺，Cu²⁺Either one or both of them.

The preparation method of the three-dimensional nitrogen-doped carbon-based material loaded bimetallic phosphide bifunctional catalyst comprises the following steps: in the step (3), the inert electrode is any one of conductive glass, a glassy carbon electrode and a platinum electrode.

The preparation method of the three-dimensional nitrogen-doped carbon-based material loaded bimetallic phosphide bifunctional catalyst comprises the following steps: the three-dimensional nitrogen-doped carbon-based material is a composition of melamine and carbon nanotubes, and the specific surface area reaches 150m 2/g.

The preparation method of the three-dimensional nitrogen-doped carbon-based material loaded bimetallic phosphide bifunctional catalyst comprises the following steps: the bimetallic phosphide is nano-particles with the diameter of 5-20 nm.

The preparation method of the three-dimensional nitrogen-doped carbon-based material loaded bimetallic phosphide bifunctional catalyst comprises the following steps: the specific surface area of the three-dimensional nitrogen-doped carbon-based material loaded double-metal phosphide double-function composite catalyst reaches 420m²/g。

The preparation method of the three-dimensional nitrogen-doped carbon-based material loaded bimetallic phosphide bifunctional catalyst comprises the following steps: in the step (3), the precursors of the transition metal phosphide are sodium dihydrogen phosphite and any two of nickel acetate, iron acetate, cobalt acetate, manganese acetate and copper acetate.

The preparation method of the three-dimensional nitrogen-doped carbon-based material loaded bimetallic phosphide bifunctional catalyst comprises the following steps: the preparation method of the precursor of the transition metal phosphide can be divided into two steps:

1) loading a transition metal: loading transition metal elements by using an in-situ electrochemical reduction method;

2) phosphorization of transition metal: the phosphating of the transition metal was carried out with sodium dihydrogen phosphite at 350 ℃ under nitrogen.

In addition, the invention also provides application of the bimetallic phosphide dual-function catalyst loaded on the three-dimensional nitrogen-doped carbon-based material, wherein the three-dimensional nitrogen-doped carbon-based material has a typical spatial configuration of uniform cross support of a graphene sheet layer and a nanotube, the size of the nitrogen-doped graphene sheet layer is nano-scale, and the nitrogen-doped graphene sheet layer is 100-300 nm; the diameter of the nitrogen-doped carbon nanotube is 8-15nm, the length of the nitrogen-doped carbon nanotube is 100nm-1 mu m, the material has a larger specific surface area, and also has good conductivity and a large number of three-dimensional space structures, and the doping of nitrogen element in the material provides more active sites, the three-dimensional nitrogen-doped carbon-based material is beneficial to the effective load of transition metal, and is beneficial to enhancing the ORR and OER catalytic performance of the composite catalyst, the double-transition metal phosphide has the synergistic effect of metal and phosphorus, and the catalytic performance of the double-transition metal phosphide is improved in a controllable manner by adjusting the metal type.

Compared with the prior art, the invention has the following beneficial effects:

1) the raw materials are cheap, easy to prepare and rich in reserves.

2) The preparation method simplifies the process, shortens the flow and is easy to control.

3) The synthesized composite catalyst has a large effective specific surface area, clear components and clear catalytic activity centers.

4) The composite catalyst synthesized by the invention has dual-functional catalytic performance of ORR and OER under an alkaline condition, the ORR performance is close to that of a commercial 20 wt% platinum/carbon catalyst, the potential of the OER when the current density reaches 10mA/cm2 is close to that of mesoporous ruthenium dioxide reported in the literature, and the methanol poisoning resistance is superior to that of a commercial noble metal catalyst.

Drawings

Fig. 1 is a Scanning Electron Microscope (SEM) atlas of the three-dimensional nitrogen-doped carbon-based material supported nickel-iron bimetallic phosphide bifunctional composite catalyst of the present invention.

Fig. 2 is a Transmission Electron Microscope (TEM) map of the three-dimensional nitrogen-doped carbon-based material supported nickel iron bimetallic phosphide bifunctional composite catalyst of the present invention.

Fig. 3 is a BET nitrogen isothermal adsorption and desorption curve of the three-dimensional nitrogen-doped carbon-based material loaded nickel-iron bimetallic phosphide bifunctional composite catalyst.

FIG. 4 is an ORR polarization curve of the three-dimensional nitrogen-doped carbon-based material supported nickel-iron bimetallic phosphide dual-function composite catalyst and 20 wt% Pt/C.

FIG. 5 is an I-t curve of the methanol poisoning resistance test of the three-dimensional nitrogen-doped carbon-based material supported nickel-iron bimetallic phosphide dual-function composite catalyst and 20 wt% Pt/C.

FIG. 6 is an OER polarization curve of the three-dimensional nitrogen-doped carbon-based material loaded nickel-iron bimetallic phosphide dual-function composite catalyst and 20 wt% Pt/C.

Detailed Description

The invention is further described below with reference to the figures and examples.

EXAMPLE 1

Ultrasonically dispersing 450mg of melamine (national drug group chemical reagent Co., Ltd., analytical purity) and 300mg of carbon nanotubes (Chinese academy of sciences organic chemistry Co., Ltd.) in ultrapure water for 30 minutes, drying at 80 ℃, and carrying out heat treatment at 550 ℃ for 2 hours under nitrogen to obtain a three-dimensional nitrogen-doped carbon-based material (3D-C);

ultrasonically dispersing 500mg of three-dimensional nitrogen-doped carbon-based material, 1g of nickel acetate hexahydrate and 1g of ferric acetate hexahydrate in 5mL of ethanol for 1 hour, and drying the mixed solution on the surface of a glassy carbon electrode at 80 ℃;

in a neutral phosphoric acid buffer solution, taking the inert glassy carbon electrode of the load mixture as a working electrode, a platinum wire as a counter electrode and a Saturated Calomel Electrode (SCE) as a reference electrode, electrolyzing for 1 minute under the current of-10 mA, washing for 5 times by using ultrapure water, and drying to obtain a precursor;

and (3) reacting the precursor with 200mg of sodium dihydrogen phosphite at 350 ℃ for 2 hours at the temperature rising speed of 2.5 ℃/min in the nitrogen atmosphere, and cooling to obtain the three-dimensional nitrogen-doped carbon-based material loaded nickel-iron bimetallic phosphide bifunctional composite catalyst.

EXAMPLE 2

Adopts a standard three-electrode system to load a nickel-iron bimetallic phosphide dual-function composite catalyst (NiP) on a three-dimensional nitrogen-doped carbon-based material₂/FeP₂3D-C) carrying out an ORR catalytic performance test. The testing apparatus is a CH Instrument Model 760D potentistat system. The Hg/HgO electrode is a reference electrode, the C rod is a counter electrode, and the glassy carbon electrode is a working electrode. The solution was 0.1M KOH, the scan rate was 10mV/s, the electrode rotation speed was 1600rpm, and the temperature was room temperature. Before testing, the electrolyte was saturated with oxygen for 30 minutes, the retention time was set to 30s, and the ring voltage was set to 0.8V. As can be seen from the figure, NiP₂/FeP₂The initial potential of the/3D-C catalyst is 0.020V, which is shifted by 18mV compared with the initial potential (0.002V) of Pt/C; NiP₂/FeP₂Half of a/3D-C catalystThe wave potential is-0.115V, which is shifted by 10mV more than the half-starting potential (-0.105V) of Pt/C; NiP₂/FeP₂The limiting current density of the/3D-C catalyst is slightly larger than that of Pt/C. The result shows that the three-dimensional nitrogen-doped carbon-based material loaded nickel-iron bimetallic phosphide dual-function composite catalyst (NiP)₂/FeP₂ORR catalytic activity of/3D-C) was slightly better than that of commercial 20 wt% Pt/C.

EXAMPLE 3

Adopts a standard three-electrode system to load a nickel-iron bimetallic phosphide dual-function composite catalyst (NiP) on a three-dimensional nitrogen-doped carbon-based material₂/FeP₂the/3D-C) methanol resistance test. The Hg/HgO electrode is a reference electrode, the C rod is a counter electrode, and the glassy carbon electrode is a working electrode. The solution was 0.1M KOH, the scan rate was 10mV/s, the electrode rotation speed was 1600rpm, the temperature was room temperature, and the test voltage was-0.4V. It can be seen from the figure that 2M methanol, NiP, was added at around 300s₂/FeP₂The catalytic current of the/3D-C is not changed obviously, while the catalytic current of the Pt/C is reduced sharply. The results show that NiP₂/FeP₂The catalytic capability of the/3D-C catalyst is not obviously affected after methanol is added, namely the three-dimensional nitrogen-doped carbon-based material loaded nickel-iron bimetallic phosphide dual-functional composite catalyst (NiP)₂/FeP₂the/3D-C) methanol resistance is significantly better than commercial 20 wt% Pt/C.

EXAMPLE 4

Adopts a standard three-electrode system to load a nickel-iron bimetallic phosphide dual-function composite catalyst (NiP) on a three-dimensional nitrogen-doped carbon-based material₂/FeP₂the/3D-C) was tested for OER catalytic performance. The testing apparatus is a CH Instrument Model 760D potentistat system. The Saturated Calomel Electrode (SCE) is a reference electrode, the C rod is a counter electrode, and the glassy carbon electrode is a working electrode. The solution was 0.1M KOH, the scan rate was 10mV/s, the electrode rotation speed was 1600rpm, and the temperature was room temperature. As can be seen from the figure, NiP₂/FeP₂The potential of the/3D-C catalyst at 10mA/cm2 is 0.639V, and the catalyst is more noble metal RuO₂(0.714V) and Pt/C (1.071V) were low at 10mA/cm 2. The result shows that the three-dimensional nitrogen-doped carbon-based material loaded nickel-iron bimetallic phosphide dual-functional composite catalysis is performedAgent (NiP)₂/FeP₂the/3D-C) has better catalytic activity on OER than the commercial noble metal catalysts RuO2 and Pt/C.

EXAMPLE 5

Ultrasonically dispersing 500mg of three-dimensional nitrogen-doped carbon-based material and 1g of nickel acetate hexahydrate and 1g of cobalt acetate hexahydrate in 5mL of ethanol for 1 hour, and drying the mixed solution on the surface of a glassy carbon electrode at 80 ℃; in a neutral phosphoric acid buffer solution, taking the inert glassy carbon electrode of the load mixture as a working electrode, a platinum wire as a counter electrode and a Saturated Calomel Electrode (SCE) as a reference electrode, electrolyzing for 1 minute under the current of-10 mA, washing for 5 times by using ultrapure water, and drying to obtain a precursor; and (3) reacting the precursor with 200mg of sodium dihydrogen phosphite at the temperature of 350 ℃ for 2 hours at the temperature rising speed of 2.5 ℃/min in a nitrogen atmosphere, and cooling to obtain the three-dimensional nitrogen-doped carbon-based material loaded nickel-cobalt bimetallic phosphide bifunctional composite catalyst. The potential of the catalyst at 10mA/cm2 is 0.715V, which is more noble than RuO catalyst₂The potential at 10mA/cm2 (0.714V) was comparable to that at 10mA/cm2 (1.071V) of Pt/C. The result shows that the catalytic activity of the three-dimensional nitrogen-doped carbon-based material loaded nickel-cobalt bimetallic phosphide bifunctional composite catalyst on OER and the commercial noble metal catalyst RuO₂Is equivalent to and superior to Pt/C.

Ultrasonically dispersing 500mg of three-dimensional nitrogen-doped carbon-based material, 1g of nickel acetate hexahydrate and 1g of manganese acetate hexahydrate in 5mL of ethanol for 1 hour, and drying the mixed solution on the surface of a glassy carbon electrode at 80 ℃; in a neutral phosphoric acid buffer solution, taking the inert glassy carbon electrode of the load mixture as a working electrode, a platinum wire as a counter electrode and a Saturated Calomel Electrode (SCE) as a reference electrode, electrolyzing for 1 minute under the current of-10 mA, washing for 5 times by using ultrapure water, and drying to obtain a precursor; and (3) reacting the precursor with 200mg of sodium dihydrogen phosphite at the temperature of 350 ℃ for 2 hours at the temperature rising speed of 2.5 ℃/min in a nitrogen atmosphere, and cooling to obtain the three-dimensional nitrogen-doped carbon-based material loaded nickel-manganese bi-metal phosphide dual-functional composite catalyst. The catalyst has a potential of 0.792V at 10mA/cm2, and is a more noble metal catalyst RuO₂The potential at 10mA/cm2 (0.714V) was higher than that at 10mA/cm2 (1.071V). The results show three-dimensional nitrogen dopingThe catalytic activity of the carbon-based material loaded nickel-manganese bimetallic phosphide bifunctional composite catalyst on OER is slightly lower than that of a commercial noble metal catalyst RuO₂Is superior to Pt/C.

Ultrasonically dispersing 500mg of three-dimensional nitrogen-doped carbon-based material and 1g of ferric acetate hexahydrate and 1g of cobalt acetate hexahydrate in 5mL of ethanol for 1 hour, and drying the mixed solution on the surface of a glassy carbon electrode at 80 ℃; in a neutral phosphoric acid buffer solution, taking the inert glassy carbon electrode of the load mixture as a working electrode, a platinum wire as a counter electrode and a Saturated Calomel Electrode (SCE) as a reference electrode, electrolyzing for 1 minute under the current of-10 mA, washing for 5 times by using ultrapure water, and drying to obtain a precursor; and (3) reacting the precursor with 200mg of sodium dihydrogen phosphite at 350 ℃ for 2 hours at the temperature rising speed of 2.5 ℃/min in the nitrogen atmosphere, and cooling to obtain the three-dimensional nitrogen-doped carbon-based material loaded iron-cobalt bimetallic phosphide dual-function composite catalyst. The potential of the catalyst at 10mA/cm2 is 0.894V, which is more noble metal catalyst RuO₂The potential at 10mA/cm2 (0.714V) was higher than that at 10mA/cm2 (1.071V). The result shows that the catalytic activity of the three-dimensional nitrogen-doped carbon-based material loaded cobalt-iron bimetallic phosphide bifunctional composite catalyst on OER is slightly lower than that of a commercial noble metal catalyst RuO2 and is better than that of Pt/C.

The three-dimensional nitrogen-doped carbon-based material prepared by the invention has a typical spatial configuration of uniform cross support of a graphene sheet layer and a nanotube, wherein the size of the nitrogen-doped graphene sheet layer is nano-scale and is 100-300 nm; the diameter of the nitrogen-doped carbon nano tube is 8-15nm, and the length of the nitrogen-doped carbon nano tube is 100nm-1 mu m. The material has a large specific surface area, good conductivity and a large number of three-dimensional void structures, and more active sites such as graphite nitrogen, pyridine nitrogen, pyrrole nitrogen and the like are provided by doping of nitrogen elements in the material. The three-dimensional nitrogen-doped carbon-based material is beneficial to effective loading of transition metal and enhancing the ORR and OER catalytic performance of the composite catalyst.

The precursor of the transition metal phosphide is sodium dihydrogen phosphite and any two of nickel acetate, iron acetate, cobalt acetate, manganese acetate and copper acetate, and the preparation method can be divided into two steps: 1) loading a transition metal: and loading the transition metal element by using an in-situ electrochemical reduction method. 2) Phosphorization of transition metal: the phosphating of the transition metal was carried out with sodium dihydrogen phosphite at 350 ℃ under nitrogen. The preparation method has the advantages of convenient operation, simple process and strong controllability, greatly shortens the preparation time and saves resources. The metal nano particles in the three-dimensional nitrogen-doped carbon-based material loaded double-metal phosphide double-function composite catalyst synthesized by the method are uniformly distributed, and the diameter of the metal nano particles is 5-20 nm.