CN109267095B

CN109267095B - Novel nickel phosphide catalyst and preparation method thereof

Info

Publication number: CN109267095B
Application number: CN201811409939.8A
Authority: CN
Inventors: 赵学波; 闫理停; 姜慧敏; 王颖
Original assignee: China University of Petroleum East China
Current assignee: China University of Petroleum East China
Priority date: 2018-11-23
Filing date: 2018-11-23
Publication date: 2021-01-08
Anticipated expiration: 2038-11-23
Also published as: CN109267095A

Abstract

The invention relates to a novel nickel phosphide catalyst, which has larger specific surface area and pore volume and is distributed in a multi-stage pore distributionThe catalyst is Ni₂The P catalytic active center is uniformly dispersed in the nitrogen-phosphorus co-doped carbon network skeleton. The preparation method comprises the following steps: 1) preparing a MOFs precursor containing nitrogen and phosphorus atoms: respectively weighing organic ligands containing phosphorus and nitrogen and nickel salt, dissolving in a certain amount of deionized water, and fully stirring to obtain three solutions; then, synthesizing a nitrogen-phosphorus atom-containing MOFs precursor by using a micro-droplet method; 2) and placing a certain amount of MOFs precursor containing nitrogen and phosphorus atoms into a corundum porcelain boat, and then placing the corundum porcelain boat into a tubular furnace for calcination to obtain the nickel phosphide catalyst with uniformly distributed nitrogen-phosphorus co-doped porous carbon-coated catalytic centers. The catalyst has larger specific surface area and pore volume, is beneficial to the implementation of electrochemical catalysis, hydrodesulfurization, selective hydrogenation and other hydrogenation reactions, and has wide application prospect.

Description

Novel nickel phosphide catalyst and preparation method thereof

Technical Field

The invention relates to the technical field of materials and energy, in particular to a novel nickel phosphide catalyst and a preparation method thereof.

Background

With the rapid development of the world population and economy, energy resources are regarded as the most basic requirements for the development of the human society, but fossil fuels such as coal, petroleum and the like are gradually exhausted due to limited reserves and non-regeneration, so that the development of the society and the economy is greatly limited. Meanwhile, a series of environmental problems generated in the development and utilization process of fossil energy also affect the health and development of human beings. Therefore, in consideration of economic sustainable development and environmental protection, the development and utilization of green renewable clean energy is a critical problem facing the energy technology field in need of solution. The hydrogen energy is energy generated by the reaction of the hydrogen and the oxygen, and has the advantages of high energy density, wide source, zero carbon emission in the using process and reproducibility as a clean and environment-friendly secondary energy source, so that the hydrogen energy is widely favored; in addition, the hydrogen energy can also be used as an energy storage intermediate, other intermittent and unstable clean energy sources such as wind energy, solar energy and the like are converted into the hydrogen energy to be stored and transported, and the hydrogen energy can be utilized in the form of the hydrogen energy when needed. Therefore, among these new energy sources, hydrogen energy is regarded as the best energy carrier, and research on development of hydrogen energy is becoming more and more frequent, and how to efficiently produce hydrogen at low cost is the key to deep utilization of hydrogen energy. The electrocatalytic decomposition of water for hydrogen production is considered to be one of the most promising hydrogen production technologies at present due to wide raw material sources, simple process and convenient operation. The electrocatalytic decomposition of water to produce hydrogen mainly comprises two key core reactions, namely an electrochemical Oxygen Evolution Reaction (OER) on an anode and an electrochemical Hydrogen Evolution Reaction (HER) on a cathode. However, in the process of electrocatalytic decomposition of water, OERs and HERs generally require a high overpotential for reaction to overcome the reaction energy barrier, which greatly increases the energy loss during the reaction, and thus, an efficient, stable and inexpensive electrocatalyst is required to accelerate the reaction kinetics of the catalytic reaction and reduce the energy consumption of the reaction. Currently, the most effective HER and OER catalysts are Pt-based catalysts and Ru and Ir-based catalysts of noble metals, respectively, but the noble metals have high cost and low reserves, and the application of electrocatalytic decomposition of water in industry is seriously hindered. Therefore, how to develop a catalyst with abundant reserves, low price, easy availability, excellent catalytic performance and stability is a key point for limiting the utilization of hydrogen energy.

In recent years, transition metal phosphide has attracted much attention of scientists, especially nickel phosphide (Ni), due to its abundant reserves, low price and catalytic activity comparable to noble metals platinum and iridium₂P) is the representative catalyst, the catalytic performance of the catalyst can be named as phosphide, and the catalyst has wide application prospect. In addition, theoretical calculation and earlier scientific research prove that the catalytic activity of the catalyst can be obviously improved by multi-element doping, which mainly benefits from the synergistic effect among active centers. For example, the doping element can optimize the electronic structure of the catalyst body, reduce the energy barrier of the mass-charge transfer of the catalyst, and further promote the catalytic reaction. However, since the multi-element doped catalyst is limited by the valence state of the element and the composition of the phase in the process of forming the composite material, the difficulty of directionally synthesizing a uniform composite phase is great. The metal-organic framework compounds (MOFs) are one-dimensional, two-dimensional or three-dimensional porous network structures formed by metal ions or metal clusters and organic ligands in a self-assembly mode, and have wide application rangeNovel crystal materials with wide application prospect. Due to the characteristics of controllable pore structure, large specific surface area, unsaturated coordination bonds and the like, the porous material has wide application prospects in various fields such as gas storage, gas separation, biomedicine, photoelectromagnetism and the like, and becomes one of leading-edge hot spots in the field of materials. In addition, due to the uniform distribution of metal central atom level in the MOFs framework and the higher content of metal elements, the MOFs material is an ideal template for preparing the porous metal phosphide composite material with high dispersity. And by virtue of the characteristic of uniform distribution of all elements in the MOFs framework, the synthesis of the multi-element doped material can be carried out by introducing heteroatoms such as nitrogen, phosphorus and the like into the organic ligand. Compared with other supported catalysts, the better compatibility of MOFs to different metal centers greatly simplifies the process of synthesizing homogeneous single metal/multi-metal phosphide. Due to the uniform distribution of the metal center and the carbon-containing organic ligand in the metal organic framework material, the composite material derived from the metal organic framework material often has a special internal electronic structure and surface composition, and the special composition form is greatly different from the surface-loaded active center, so that the activity of the catalytic center can be exerted more efficiently.

Chinese patent document CN 106475122A discloses Ni for preparing three-dimensional step pore structure at low temperature₂A process for the preparation of a P catalyst, the process comprising the steps of: (1) synthesizing a nickel-based metal organic framework material by a conventional method; (2) heat treating the nickel-based metal organic frame material and hypophosphite for 1-500min at the temperature of 200-350 ℃ under the protection of inert gas to obtain Ni with a three-dimensional step pore structure₂And (3) a P catalyst. The invention obtains the hierarchical pore Ni with higher specific surface area through one-step phosphating reaction by taking a nickel-based metal organic framework as a precursor and adding a phosphorus source₂And (3) a P catalyst. However, this method still requires an additional phosphorus source to react. Chinese patent document CN 107790164A nitrogen-phosphorus co-doped porous carbon-coated cuprous phosphide composite catalyst and a preparation method thereof, wherein the method comprises the following steps: (1) synthesizing a Cu-NPMOF precursor by using a double organic ligand containing nitrogen and phosphorus; (2) calcining the Cu-NPMOF precursor under nitrogen to obtain black powder, ultrasonically washing the black powder by using dilute hydrochloric acid, and drying to obtain solid powder; (3) Mixing the obtained black powder with sodium hypophosphite, fully grinding, calcining in a nitrogen atmosphere to obtain black powder, washing with deionized water, centrifuging, drying to obtain a target product, and using the obtained catalyst for electrocatalytic hydrogen production. Chinese patent document CN 107694581 a discloses the application of heteroatom-doped porous carbon-coated cuprous phosphide composite catalyst, which is similar to the preparation method of chinese patent document CN 107790164 a, and the catalyst is applied in the aspects of electrocatalytic reaction and zinc-air battery. Said invention contains ligand of multicomponent hetero atom, and utilizes multistep reaction to obtain the composite catalyst with higher specific surface area. However, in the method, nitrogen and phosphorus heteroatoms are introduced through MOFs precursors, and a phosphorus source is still required to be added to obtain the phosphide catalyst. The more the reaction path involves, the more unfavorable the utilization rate of atoms and the reaction efficiency in the synthesis of materials, because of the inevitable energy loss and side reactions in the actual reaction.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a novel nickel phosphide catalyst and a preparation method thereof. The invention adopts a micro-droplet method to rapidly and continuously synthesize the MOFs material containing nitrogen and phosphorus multi-element heteroatoms as a precursor, and directly prepares the nickel phosphide catalyst with uniformly distributed nitrogen and phosphorus co-doped porous carbon-coated catalytic centers through one-step simple heat treatment, and the nickel phosphide catalyst has excellent catalytic reaction activity. The preparation method of the invention prepares the nickel phosphide catalyst with uniformly distributed nitrogen-phosphorus co-doped porous carbon-coated catalytic centers by a simple, high-efficiency, low-cost and easy-industrialization method. The prepared catalyst has larger specific surface area and pore volume, is distributed in a multi-level pore, and Ni₂The P catalytic active center is uniformly dispersed in the nitrogen-phosphorus co-doped carbon network skeleton, so that the method is favorable for carrying out electrochemical catalysis, hydrodesulfurization, selective hydrogenation and other hydrogenation reactions, and has wide application prospect.

In order to solve the technical problems, the technical scheme provided by the invention is as follows: a novel nickel phosphide catalyst with large specific surface area and pore volume and high activityStage pore distribution, the catalyst is Ni₂The P catalytic active center is uniformly dispersed in the nitrogen-phosphorus co-doped carbon network skeleton.

A preparation method of a novel nickel phosphide catalyst comprises the following steps:

1) preparing a MOFs precursor containing nitrogen and phosphorus atoms: respectively weighing organic ligands containing phosphorus and nitrogen and nickel salt, dissolving in a certain amount of deionized water, and fully stirring to obtain three solutions; then, synthesizing a nitrogen-phosphorus atom-containing MOFs precursor by using a micro-droplet method;

2) and (3) placing a certain amount of MOFs precursor containing nitrogen and phosphorus atoms in a corundum porcelain boat, then placing the corundum porcelain boat in a tubular furnace, heating to 600-1100 ℃, and calcining for 0.5-12 hours to obtain the nickel phosphide catalyst with uniformly distributed nitrogen and phosphorus co-doped porous carbon-coated catalytic centers.

Further, the phosphorus-containing organic ligand described in step 1) includes 2,4, 6-trimethylbenzene-1, 3, 5-trimethylenetriasphonic acid ligand, 2,4, 6-trimethylbenzene-1, 3-dimethylene diphosphonic acid, 2, 5-dimethylbenzene-1, 4-dimethylene diphosphonic acid, p-xylylene diphosphonic acid, 2, 5-dimethylbenzene-1, 4-diphosphonic acid, 2, 4-diphosphonic acid trimethylbenzene, methyl phosphonic acid, hydroxy ethylidene diphosphonic acid, aminomethyl phosphonic acid, amino trimethyl phosphonic acid, zoledronic acid. As an improvement, the phosphorus-containing organic ligands comprise 2,4, 6-trimethylbenzene-1, 3, 5-trimethylene triphosphonic acid ligand and 2,4, 6-trimethylbenzene-1, 3-dimethylene diphosphonic acid; most preferably, the phosphorus-containing organic ligand comprises a 2,4, 6-trimethylbenzene-1, 3, 5-trimethylenetriaphosphonic acid ligand.

Further, the concentration of the phosphorus-containing organic ligand in the step 1) is 0.05-0.5 mol/L. As a modification, the concentration of the phosphorus-containing organic ligand is 0.10 mol/L.

Further, the nitrogen-containing organic ligand in the step 1) comprises 4,4 '-bipyridine, 2,2' -bipyridine, phenanthroline and pyrazine.

Further, the concentration of the nitrogen-containing organic ligand in the step 1) is 0.05-0.5 mol/L. As a modification, the concentration of the nitrogen-containing organic ligand is 0.15 mol/L.

Further, the nickel salt in step 1) includes hydrates of nickel sulfate, nickel nitrate, nickel chloride and nickel acetate. As an improvement, the nickel salt is a hydrate of nickel sulfate and nickel nitrate.

Further, the concentration of the nickel salt in the step 1) is 0.05-0.5 mol/L. As a modification, the concentration of the nickel salt is 0.15 mol/L.

Further, the synthesis method of the MOFs precursors containing nitrogen and phosphorus atoms in step 1) includes a microdroplet synthesis method and a hydrothermal synthesis method. As an improvement, the synthesis method of the MOFs precursor containing nitrogen and phosphorus atoms is a micro-droplet synthesis method.

Further, the reaction conditions of the microdroplet synthesis method of the MOFs precursors containing nitrogen and phosphorus atoms in the step 1) are as follows: an injection pump in the micro-droplet continuous synthesis device is utilized to pump an organic ligand solution and a nickel salt solution into a mixer, the mixture reacts for 20 to 200 minutes in a reaction zone at the temperature of 80 to 100 ℃, and then a subsequent collection device is used to collect a sample, separate and clean the sample, so as to obtain an MOFs precursor containing nitrogen and phosphorus atoms; as a modification, the temperature in the reaction zone was 100 ℃ and the reaction time was 80 minutes.

Further, the reaction conditions of the hydrothermal synthesis method of the MOFs precursors containing nitrogen and phosphorus atoms in step 1) are as follows: transferring the mixed solution into a polytetrafluoroethylene-lined reaction kettle, heating to 120-150 ℃, reacting for 6-72 hours, centrifugally separating the product, and cleaning to obtain an MOFs precursor containing nitrogen and phosphorus atoms; as a modification, the reaction temperature was 140 ℃ and the reaction time was 72 hours.

Further, the mass of the MOFs precursor containing nitrogen and phosphorus atoms in the step 2) is 0.05-10 g.

Further, the inert atmosphere in the step 2) is argon, nitrogen or helium; as a modification, the inert atmosphere is nitrogen.

Further, the flow rate of the inert gas in the step 2) is 1-500 mL/min; as a modification, the flow rate of the inert gas is 20-100 mL/min.

Further, in the step 2), the heating rate is 1-20 ℃/min; as an improvement, the heating rate is 5-10 ℃/min.

Further, the heat treatment temperature in the step 2) is 600-1100 ℃, and the heat treatment time is 0.5-12 hours; as an improvement, the heat treatment temperature is 800-1000 ℃, and the heat treatment time is 0.5-5 hours; further improved, the heat treatment temperature is 900 ℃, and the heat treatment time is 2 hours.

The invention utilizes a micro-droplet reaction system to rapidly and continuously synthesize the MOFs material containing nitrogen and phosphorus heteroatoms, and obtains the hierarchical porous Ni coated with the nitrogen and phosphorus co-doped carbon layer with controllable element content through one-step simple heat treatment₂P catalyst (Ni)₂P NPHPN). In addition, by simply controlling the temperature and time of the heat treatment, a series of Ni having different specific surface areas and doping ratios can be synthesized₂P NPHPN catalyst, Ni obtained due to uniform distribution of N, P, Ni and C in MOFs precursor₂Ni in P NPHPN catalyst₂P is uniformly dispersed in the nitrogen-phosphorus co-doped carbon layer, and the specific surface area of the material can reach 758.78m²·g^-1。

The method utilizes the mode of carrying out one-step pyrolysis on the MOFs precursor containing nitrogen, phosphorus and nickel, does not damage the special morphology structure of the precursor, does not need to add a phosphorus source, does not need further washing and purification on the catalyst, has simple process and is beneficial to large-scale production.

The invention has the following beneficial effects:

1. according to the invention, a nitrogen-phosphorus-codoped carbon layer-coated hierarchical porous Ni which is uniformly distributed with N, P, Ni and C and is coated by a nitrogen-phosphorus-codoped carbon layer can be obtained by using a metal organic framework material containing nitrogen, phosphorus and nickel as a precursor through a simple reaction mode of one-step heat treatment₂And (3) a P catalyst. Compared with the traditional supported catalyst, the catalyst obtained by the invention has more uniform catalytic activity distribution and obvious advantages, and the composite catalyst with uniformly doped multi-element heteroatoms can be obtained by one-step reaction. The process has low requirements on reaction devices, does not involve harmful gases, organic solvents and other reactants, has simple process and is suitable for industrial production.

2. The nitrogen-phosphorus co-doped carbon layer-coated hierarchical porous Ni₂The P catalyst has high nitrogen and phosphorus content and large specific surface area (572.9-758.8 m)²G) and pore bodiesProduct (0.32-0.41 cm)³/g) and hierarchical pore structure, more Ni can be exposed₂P catalyzes the active site, and the doping of nitrogen, phosphorus, carbon can obtain more defect sites, can further improve the catalytic effect of catalyst with the synergistic effect of nickel phosphide active center, in addition, carbon network skeleton also can improve the matter charge transfer efficiency in the catalysis process, and then improve the catalytic effect of catalyst.

Drawings

FIG. 1 is a schematic view of a microdroplet continuous synthesis apparatus according to the present invention;

FIG. 2 is an X-ray powder diffraction Pattern (PXRD) of the MOFs material containing nitrogen and phosphorus atoms prepared in example 1;

FIG. 3 shows the nitrogen-phosphorus co-doped carbon layer-coated hierarchical porous Ni prepared in example 1₂PXRD pattern for the P catalyst;

FIG. 4 shows the nitrogen-phosphorus co-doped carbon layer-coated hierarchical porous Ni prepared in example 1₂Scanning Electron Microscope (SEM) photograph of P catalyst;

FIG. 5 shows the nitrogen-phosphorus co-doped carbon layer-coated hierarchical porous Ni prepared in example 1₂Transmission Electron Microscope (TEM) photograph of the P catalyst;

FIG. 6 shows the nitrogen-phosphorus co-doped carbon layer-coated hierarchical porous Ni prepared in example 1₂High power transmission electron microscope (HRTEM) photograph of P catalyst;

FIG. 7 shows the nitrogen-phosphorus co-doped carbon layer-coated hierarchical porous Ni prepared in example 1₂EDS of the P catalyst corresponds to an element mapping distribution diagram;

FIG. 8 shows the nitrogen-phosphorus co-doped carbon layer-coated hierarchical porous Ni prepared in example 1₂The nitrogen physical adsorption curve and the aperture distribution diagram of the P catalyst;

FIG. 9 shows the nitrogen-phosphorus co-doped carbon layer-coated hierarchical porous Ni prepared in example 1₂Linear sweep voltammetry profile of P-catalyst catalyzed electrochemical Oxygen Evolution Reaction (OER).

FIG. 10 shows the nitrogen-phosphorus co-doped carbon layer-coated hierarchical porous Ni prepared in example 1₂Linear sweep voltammetry profile of P-catalyst catalyzed electrochemical Hydrogen Evolution Reaction (HER).

FIG. 11Nitrogen-phosphorus co-doped carbon layer coated hierarchical porous Ni prepared for example 1₂Linear sweep voltammetry curve of P-catalyst catalyzed total decomposition of water.

Detailed Description

The present invention will be further described with reference to the following examples, but is not limited thereto. Meanwhile, the experimental methods described in the following examples are all conventional methods unless otherwise specified; the reagents and materials are commercially available, unless otherwise specified.

The nitrogen-phosphorus co-doped carbon layer-coated hierarchical porous Ni prepared by the method₂The phase of the P catalyst was determined by X-ray powder diffractometry using an X' pert PRO powder diffractometer from parnacho, netherlands.

The nitrogen-phosphorus co-doped carbon layer-coated hierarchical porous Ni prepared by the method₂The morphology of the P catalyst is shown by a field emission Scanning Electron Microscope (SEM) photograph and a mapping image of the corresponding element, using a JSM-7500F field emission scanning electron microscope, japan.

The nitrogen-phosphorus co-doped carbon layer-coated hierarchical porous Ni prepared by the method₂The internal morphology and elemental distribution of the P-catalyst were shown by Transmission Electron Microscope (TEM) photographs using a japanese JEOL JEM2100F transmission electron microscope.

The nitrogen-phosphorus co-doped carbon layer-coated hierarchical porous Ni prepared by the method₂The specific surface area of the P catalyst is shown by a low-temperature nitrogen adsorption and desorption curve, and Autosorb-iQ of Congta corporation in America is adopted₂Full-automatic specific surface and aperture distribution analyzer.

The nitrogen-phosphorus co-doped carbon layer-coated hierarchical porous Ni prepared by the method₂The electrocatalytic performance of the P-catalyst was measured by the shanghai chen CHI760E electrochemical workstation.

Example 1

A preparation method of a nickel phosphide catalyst with uniformly distributed nitrogen-phosphorus co-doped porous carbon-coated catalytic centers comprises the following steps:

1) preparing a MOFs precursor containing nitrogen and phosphorus atoms:

dispersing nickel sulfate, 2,4, 6-trimethylbenzene-1, 3, 5-trimethylene triphosphonic acid ligand and 4,4' -bipyridyl into deionized water to prepare solutions with the concentrations of 0.15mol per liter, 0.1 mol per liter and 0.15mol per liter respectively, pumping raw materials into a mixer by using the device shown in the figure 1, feeding the raw materials into a reaction zone, wherein the temperature of the reaction zone is 100 ℃, the retention time is 80 minutes, collecting products at a pipe orifice at the tail part, centrifuging or filtering to separate the products, and obtaining the MOFs precursor containing nitrogen and phosphorus atoms.

2) Weighing 0.5g of MOFs precursor containing nitrogen and phosphorus atoms in the step 1), placing the precursor into a corundum porcelain boat, placing the porcelain boat into a tubular furnace, heating to 900 ℃ at a heating rate of 5 ℃ per minute under a nitrogen atmosphere of 30 milliliters per minute, and keeping the temperature for 2 hours (continuously blowing by using 30 milliliters per minute of nitrogen in the process), so that the nickel phosphide catalyst with uniformly distributed nitrogen and phosphorus co-doped porous carbon coated catalytic centers can be obtained.

The X-ray powder diffraction pattern of the obtained MOFs precursor containing nitrogen and phosphorus atoms is shown in fig. 2, and it is understood from fig. 2 that the MOFs precursor containing nitrogen and phosphorus atoms was successfully prepared in this example. The X-ray powder diffraction pattern of the obtained nickel phosphide catalyst with uniformly distributed nitrogen-phosphorus co-doped porous carbon-coated catalytic centers is shown in fig. 3, and the nickel phosphide prepared in the example is pure-phase Ni₂And (3) a P catalyst. As shown in fig. 4, 5 and 6, the Scanning Electron Microscope (SEM), the Transmission Electron Microscope (TEM) and the high-power transmission electron microscope (HRTEM) showed that the resulting nickel phosphide catalyst had a porous polyhedral structure as shown in fig. 4 and 5. The HRTEM of FIG. 6 shows that the active center of nickel phosphide is coated by carbon layer, and the carbon structure of several layers can not only accelerate the charge transfer efficiency of nickel phosphide in the electrocatalysis process, but also protect nickel phosphide, and improve the catalytic activity and reaction stability of the material. The uniform distribution of the elements in fig. 7 also shows that the synthesis method can obtain the uniformly dispersed nickel phosphide composite catalyst. As can be seen from the nitrogen physical adsorption curve and the pore size distribution diagram of FIG. 8, the obtained catalytic material has a high specific surface area (758.8 square meters per gram) and a distinct hierarchical pore structure, which both contribute to the exertion of the catalyst activity.

And (3) testing the electrocatalytic performance:

the polymetallic phosphide nanotube catalyst prepared in the example catalyzes electrochemical Hydrogen Evolution Reaction (HER) and Oxygen Evolution Reaction (OER), and the specific operation is as follows: 5 mg of catalyst was weighed, dispersed in 1 ml (volume ratio, ethanol: water: nafion ═ 1:1:0.05) of solvent, sonicated for over thirty minutes to give a homogeneous suspension, 5 μ l of working solution was dropped onto a rotating disk electrode of 4 mm diameter (loading 0.19 mg per square centimeter), dried thoroughly at room temperature, and analyzed and evaluated by the electrochemical workstation of shanghai chen CHI760E using a standard three-electrode system. The test method was performed using linear sweep voltammetry, with the analysis being performed in 1.0 molar potassium hydroxide solution, the test range being 0.1 to minus 0.4 volts (HER), 1.0 to 1.8 volts (OER), and the above-mentioned electrical window being the voltage relative to a standard hydrogen electrode. The full water solubility energy test adopts a two-electrode system with foamed nickel as an electrode to carry out the test, the loading capacity of the catalyst is 1.0 gram per square centimeter, and the test range of the linear sweep voltammetry is 1.0 to 1.8 volts. The above scanning speeds are all 5mv per second.

The linear sweep voltammetry graphs for the catalyzed electrochemical oxygen evolution reaction, hydrogen evolution reaction and full hydrolysis reaction are shown in fig. 9, 10 and 11. As can be seen from the figure, the obtained catalyst has the current density of 10mAcm in the two reactions of oxygen evolution and hydrogen evolution^-2The overpotentials required are only 255mV and 125mV respectively, with a significant gain effect compared to most phosphide catalytic materials that have been disclosed so far. The two electrode systems consisting of the catalyst only need 1.62V to reach 10mA cm in the process of fully decomposing water^-2The current density of (a) is superior to that of most non-noble metal catalysts. The prepared nitrogen-phosphorus co-doped porous carbon-coated nickel phosphide catalyst has a high-activity nickel phosphide crystalline phase, and a high specific surface area and a hierarchical pore mechanism can expose more catalytic active sites and a synergistic effect of defect sites provided by a nitrogen-phosphorus co-doped carbon structure. In addition, carbon in the composite catalyst can also improve the charge transfer efficiency of the catalyst in the electrocatalysis process, and the favorable factors are beneficial to the improvement of the catalytic performance of the catalyst.

Example 2

1) preparing a MOFs precursor containing nitrogen and phosphorus atoms:

dispersing nickel sulfate, 2,4, 6-trimethylbenzene-1, 3-dimethylene diphosphonic acid ligand and 4,4' -bipyridyl into deionized water to prepare solutions with the concentrations of 0.15mol per liter, 0.1 mol per liter and 0.15mol per liter respectively, pumping raw materials into a mixer by using the device shown in the attached drawing 1, feeding the raw materials into a reaction zone, wherein the temperature of the reaction zone is 100 ℃, the retention time is 80 minutes, collecting products at a pipe orifice at the tail part, and centrifuging or filtering to separate out the products, thus obtaining the MOFs precursor containing nitrogen and phosphorus atoms.

Example 3

1) preparing a MOFs precursor containing nitrogen and phosphorus atoms:

dispersing nickel sulfate, 2,4, 6-trimethylbenzene-1, 3, 5-trimethylene triphosphonic acid ligand and 4,4' -bipyridyl into deionized water to prepare solutions with the concentrations of 0.15mol per liter, 0.2 mol per liter and 0.15mol per liter respectively, pumping raw materials into a mixer by using the device shown in the figure 1, feeding the raw materials into a reaction zone, wherein the temperature of the reaction zone is 100 ℃, the retention time is 80 minutes, collecting products at a pipe orifice at the tail part, centrifuging or filtering to separate the products, and obtaining the MOFs precursor containing nitrogen and phosphorus atoms.

Example 4

1) preparing a MOFs precursor containing nitrogen and phosphorus atoms:

dispersing nickel sulfate, 2,4, 6-trimethylbenzene-1, 3, 5-trimethylene triphosphonic acid ligand and 2,2' -bipyridyl into deionized water to prepare solutions with the concentrations of 0.15mol per liter, 0.1 mol per liter and 0.15mol per liter respectively, pumping raw materials into a mixer by using the device shown in the figure 1, feeding the raw materials into a reaction zone, wherein the temperature of the reaction zone is 100 ℃, the retention time is 80 minutes, collecting products at a pipe orifice at the tail part, centrifuging or filtering to separate the products, and obtaining the MOFs precursor containing nitrogen and phosphorus atoms.

Example 5

1) preparing a MOFs precursor containing nitrogen and phosphorus atoms:

dispersing nickel sulfate, 2,4, 6-trimethylbenzene-1, 3, 5-trimethylene triphosphonic acid ligand and 4,4' -bipyridyl into deionized water to prepare solutions with the concentrations of 0.15mol per liter, 0.1 mol per liter and 0.3 mol per liter respectively, pumping raw materials into a mixer by using the device shown in the figure 1, feeding the raw materials into a reaction zone, wherein the temperature of the reaction zone is 100 ℃, the retention time is 80 minutes, collecting products at a pipe orifice at the tail part, centrifuging or filtering to separate the products, and obtaining the MOFs precursor containing nitrogen and phosphorus atoms.

Example 6

1) preparing a MOFs precursor containing nitrogen and phosphorus atoms:

dispersing nickel sulfate, 2,4, 6-trimethylbenzene-1, 3, 5-trimethylene triphosphonic acid ligand and 4,4' -bipyridyl into deionized water to prepare solutions with the concentrations of 0.15mol per liter, 0.1 mol per liter and 0.15mol per liter respectively, pumping raw materials into a mixer by using the device shown in the figure 1, feeding the raw materials into a reaction zone, wherein the temperature of the reaction zone is 100 ℃, the retention time is 120 minutes, collecting products at a pipe orifice at the tail part, centrifuging or filtering to separate the products, and obtaining the MOFs precursor containing nitrogen and phosphorus atoms.

Example 7

1) preparing a MOFs precursor containing nitrogen and phosphorus atoms:

dispersing nickel sulfate, 2,4, 6-trimethylbenzene-1, 3, 5-trimethylene triphosphonic acid ligand and 4,4' -bipyridyl into deionized water to prepare solutions with the concentrations of 0.15mol per liter, 0.1 mol per liter and 0.15mol per liter respectively, pumping raw materials into a mixer by using the device shown in the figure 1, feeding the raw materials into a reaction zone, wherein the temperature of the reaction zone is 90 ℃, the retention time is 80 minutes, collecting products at a pipe orifice at the tail part, centrifuging or filtering to separate the products, and obtaining the MOFs precursor containing nitrogen and phosphorus atoms.

Example 8

1) preparing a MOFs precursor containing nitrogen and phosphorus atoms:

2) 3.0g of MOFs precursor containing nitrogen and phosphorus atoms in the step 1) is weighed and placed in a corundum porcelain boat, the porcelain boat is placed in a tube furnace, the porcelain boat is heated to 900 ℃ at the heating rate of 5 ℃ per minute under the nitrogen atmosphere of 30 milliliters per minute, and the temperature is kept for 2 hours (the nitrogen purging of 30 milliliters per minute is continuously used in the process), so that the nickel phosphide catalyst with uniformly distributed nitrogen and phosphorus co-doped porous carbon coated catalytic centers can be obtained.

Example 9

1) preparing a MOFs precursor containing nitrogen and phosphorus atoms:

2) Weighing 0.5g of MOFs precursor containing nitrogen and phosphorus atoms in the step 1), placing the precursor into a corundum porcelain boat, placing the porcelain boat into a tubular furnace, heating to 900 ℃ at a heating rate of 5 ℃ per minute under an argon atmosphere of 30 milliliters per minute, and keeping the temperature for 2 hours (continuously blowing by using 30 milliliters per minute of argon in the process), so that the nickel phosphide catalyst with uniformly distributed nitrogen and phosphorus co-doped porous carbon coated catalytic centers can be obtained.

Example 10

1) preparing a MOFs precursor containing nitrogen and phosphorus atoms:

2) Weighing 0.5g of MOFs precursor containing nitrogen and phosphorus atoms in the step 1), placing the precursor into a corundum porcelain boat, placing the porcelain boat into a tubular furnace, heating to 900 ℃ at a heating rate of 5 ℃ per minute under a nitrogen atmosphere of 100 milliliters per minute, and keeping the temperature for 2 hours (continuously blowing by using 100 milliliters per minute of nitrogen in the process), so that the nickel phosphide catalyst with uniformly distributed nitrogen and phosphorus co-doped porous carbon coated catalytic centers can be obtained.

Example 11

1) preparing a MOFs precursor containing nitrogen and phosphorus atoms:

2) Weighing 0.5g of MOFs precursor containing nitrogen and phosphorus atoms in the step 1), placing the precursor into a corundum porcelain boat, placing the porcelain boat into a tubular furnace, heating to 900 ℃ at a heating rate of 10 ℃ per minute in a nitrogen atmosphere of 30 milliliters per minute, and keeping the temperature for 2 hours (continuously blowing by using 30 milliliters per minute of nitrogen in the process), so that the nickel phosphide catalyst with uniformly distributed nitrogen and phosphorus co-doped porous carbon coated catalytic centers can be obtained.

Example 12

1) preparing a MOFs precursor containing nitrogen and phosphorus atoms:

2) Weighing 0.5g of MOFs precursor containing nitrogen and phosphorus atoms in the step 1), placing the precursor into a corundum porcelain boat, placing the porcelain boat into a tubular furnace, heating to 1000 ℃ at a heating rate of 5 ℃ per minute under a nitrogen atmosphere of 30 milliliters per minute, and keeping the temperature for 2 hours (continuously blowing by using 30 milliliters per minute of nitrogen in the process), so that the nickel phosphide catalyst with uniformly distributed nitrogen and phosphorus co-doped porous carbon coated catalytic centers can be obtained.

Example 13

1) preparing a MOFs precursor containing nitrogen and phosphorus atoms:

2) Weighing 0.5g of MOFs precursor containing nitrogen and phosphorus atoms in the step 1), placing the precursor into a corundum porcelain boat, placing the porcelain boat into a tubular furnace, heating to 900 ℃ at a heating rate of 5 ℃ per minute under a nitrogen atmosphere of 30 milliliters per minute, and keeping the temperature for 5 hours (continuously blowing by using 30 milliliters per minute of nitrogen in the process), so that the nickel phosphide catalyst with uniformly distributed nitrogen and phosphorus co-doped porous carbon coated catalytic centers can be obtained.

Although the invention has been described in detail hereinabove with respect to a general description and specific embodiments thereof, it will be apparent to those skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.

Claims

1. A preparation method of a nickel phosphide catalyst is characterized by comprising the following steps: the catalyst prepared by the preparation method is distributed in a multi-level pore mode, and is Ni₂The preparation method of the nickel phosphide catalyst comprises the following steps:

1) preparing a MOFs precursor containing nitrogen and phosphorus atoms: respectively weighing organic ligands containing phosphorus and nitrogen and nickel salt, dissolving in a certain amount of deionized water, and fully stirring to obtain three solutions; the concentration of the phosphorus-containing organic ligand is 0.05-0.5mol/L, the concentration of the nitrogen-containing organic ligand is 0.05-0.5mol/L, the concentration of the nickel salt is 0.05-0.5mol/L, and then a nitrogen-phosphorus atom MOFs precursor is synthesized by a micro-droplet method;

2) placing a certain amount of MOFs precursor containing nitrogen and phosphorus atoms into a corundum porcelain boat, then placing the corundum porcelain boat into a tube furnace, heating to 600-1100 ℃, calcining for 0.5-12 hours, and continuously purging by using 30 ml/min of inert atmosphere to obtain a material with a specific surface area of 572.9-758.8 m/g and a pore volume of 0.32-0.41cm³A nickel phosphide catalyst with uniformly distributed nitrogen and phosphorus co-doped porous carbon-coated catalytic centers.

2. The method of claim 1, wherein the phosphorus-containing organic ligands in step 1) comprise 2,4, 6-trimethylbenzene-1, 3, 5-trimethylenetriasphonic acid ligand and 2,4, 6-trimethylbenzene-1, 3-dimethylene diphosphonic acid, and the concentration of the phosphorus-containing organic ligand is 0.10 mol/L;

the concentration of the nitrogen-containing organic ligand in the step 1) is 0.15 mol/L;

the concentration of the nickel salt in the step 1) is 0.15 mol/L.

3. The method for preparing a nickel phosphide catalyst according to claim 1, wherein the reaction conditions of the microdroplet synthesis method of the MOFs precursors containing nitrogen and phosphorus atoms in step 1) are as follows: and (2) pumping the organic ligand solution and the nickel salt solution into a mixer by using an injection pump in the micro-droplet continuous synthesis device, reacting for 20-200 minutes in a reaction zone at 80-100 ℃, and then collecting a sample by a subsequent collecting device, separating and cleaning to obtain the MOFs precursor containing nitrogen and phosphorus atoms.

4. The method according to claim 3, wherein the reaction conditions of the microdroplet synthesis method for the MOFs precursor containing nitrogen and phosphorus atoms in step 1) are that the temperature of the reaction zone is 100 ℃ and the reaction time is 80 minutes.

5. The method according to claim 1, wherein the mass of the MOFs precursors containing nitrogen and phosphorus atoms in step 2) is 0.05-10 g.

6. The method for preparing a nickel phosphide catalyst according to claim 1, wherein the inert atmosphere in the step 2) is argon, nitrogen or helium; in the step 2), the heating rate is 1-20 ℃/min; the calcination temperature in the step 2) is 600-1100 ℃, and the heat treatment time is 0.5-12 hours.

7. The method of claim 6, wherein the inert atmosphere in step 2) is nitrogen; in the step 2), the heating rate is 5-10 ℃/min; the calcination temperature in the step 2) is 800-1000 ℃, and the heat treatment time is 0.5-5 hours.

8. The method of claim 7, wherein the calcination temperature in step 2) is 900 ℃ and the heat treatment time is 2 hours.