阅读说明：本技术 一种过渡金属掺杂镍基金属有机框架三维电极材料的制备方法及其产品和应用 (Preparation method of transition metal doped nickel-based metal organic framework three-dimensional electrode material, product and application thereof ) 是由 侯阳 程帆鹏 杨彬 雷乐成 于 2020-09-23 设计创作，主要内容包括：本发明公开了一种过渡金属掺杂镍基金属有机框架三维电极材料的制备方法：(1)将石墨片通过电化学剥离法制备得到三维导电石墨基底；(2)将步骤(1)中所获得的材料放置在二价镍盐、掺杂过渡金属盐和对苯二甲酸混合溶液中,进行一步水热反应从而在三维导电石墨基底上原位生长负载过渡金属掺杂镍基金属有机框架纳米片阵列,得到过渡金属掺杂镍基金属有机框架三维电极材料。本发明还提供了上述制备方法得到的过渡金属掺杂镍基金属有机框架三维电极材料及其在碱性电解液中电解水析氧中的应用。该三维电极材料在碱性电解液中展现出优异的催化性能,且具有良好的稳定性,在工业应用上具有较高的实用价值和前景。(The invention discloses a preparation method of a transition metal doped nickel-based metal organic framework three-dimensional electrode material, which comprises the following steps: (1) preparing a three-dimensional conductive graphite substrate from a graphite sheet by an electrochemical stripping method; (2) and (2) placing the material obtained in the step (1) in a mixed solution of divalent nickel salt, doped transition metal salt and terephthalic acid, and carrying out one-step hydrothermal reaction so as to grow a loaded transition metal doped nickel-based metal organic framework nanosheet array in situ on a three-dimensional conductive graphite substrate, thereby obtaining the transition metal doped nickel-based metal organic framework three-dimensional electrode material. The invention also provides the transition metal doped nickel-based metal organic framework three-dimensional electrode material prepared by the preparation method and application thereof in water electrolysis and oxygen evolution in alkaline electrolyte. The three-dimensional electrode material shows excellent catalytic performance in alkaline electrolyte, has good stability, and has higher practical value and prospect in industrial application.)

1. A preparation method of a transition metal doped nickel-based metal organic framework three-dimensional electrode material is characterized by comprising the following steps:

(1) preparing a three-dimensional conductive graphite substrate from a graphite sheet by an electrochemical stripping method;

(2) and (2) placing the three-dimensional conductive graphite substrate obtained in the step (1) in a mixed solution of a divalent nickel salt, a doped transition metal salt and terephthalic acid, and carrying out one-step hydrothermal reaction so as to in-situ grow a loaded transition metal doped nickel-based metal organic framework nanosheet array on the three-dimensional conductive graphite substrate, thereby obtaining the transition metal doped nickel-based metal organic framework three-dimensional electrode material.

2. The transition metal doped nickel-based metal organic framework three-dimensional electrode material as claimed in claim 1, wherein the transition metal salt is selected from cerium salt, iron salt, cobalt salt, copper salt, molybdenum salt, tungsten salt or chromium salt.

3. The transition metal doped nickel-based metal organic framework three-dimensional electrode material as claimed in claim 1, wherein the transition metal salt is cerium salt.

4. The transition metal doped nickel-based metal organic framework three-dimensional electrode material as claimed in claim 1, wherein in the step (1), the electrolyte is concentrated sulfuric acid, the electrochemical stripping condition is 5-10V DC power supply, and the reaction time is 1-3 min.

5. The preparation method of the transition metal doped nickel-based metal organic framework three-dimensional electrode material as claimed in claim 1, wherein in the step (2), the temperature of the hydrothermal reaction is 140-160 ℃.

6. The preparation method of the transition metal doped nickel-based metal organic framework three-dimensional electrode material as claimed in claim 1, wherein in the step (2), the hydrothermal reaction time is 3-6 h.

7. The preparation method of the transition metal doped nickel-based metal organic framework three-dimensional electrode material as claimed in claim 1, wherein in the step (2), the doping proportion of the transition metal salt is 1-12% of the divalent nickel salt, and the percentage is mole fraction.

8. The preparation method of the transition metal doped nickel-based metal organic framework three-dimensional electrode material as claimed in claim 1, wherein in the step (2), the doping proportion of the transition metal salt is 3-6% of the divalent nickel salt, and the percentage is mole fraction.

9. The transition metal-doped nickel-based metal organic framework three-dimensional electrode material obtained by the preparation method according to any one of claims 1 to 8, which is characterized by having a nanosheet array structure.

10. The application of the transition metal doped nickel-based metal organic framework three-dimensional electrode material as defined in claim 9 in water electrolysis and oxygen evolution in alkaline electrolyte.

Technical Field

The invention belongs to the technical field of energy conversion and environmental catalysis, and particularly relates to a preparation method of a transition metal doped nickel-based metal organic framework three-dimensional electrode material, and a product and application thereof.

Background

In order to solve the increasingly severe environmental problems caused by the rapid consumption of fossil fuels, the development of advanced, low-cost and high-efficiency energy conversion and storage devices, such as fuel cells, metal-air batteries, water electrolyzers, etc., has become a primary development goal. While further increasing the efficiency of these devices is needed to drive the development of clean and renewable energy sources. However, the slow kinetics of the anodic oxygen evolution reaction due to its four electron transfer process has been one of the limiting reactions for the development of these electrochemical energy storage and conversion devices, while the currently best electrocatalysts for anodic oxygen evolution reactions are generally noble ruthenium-based and iridium-based materials, which greatly limits their commercial large-scale applications due to the scarcity and high cost of noble materials. There is therefore an urgent need to develop low-cost, energy-efficient oxygen evolution catalysts to replace expensive precious metal materials.

In recent years, Metal Organic Framework (MOF) compounds have gained wide attention as a new class of crystalline and microporous materials. The series of MOF materials are formed by coordinative bond linkages between metal atom nodes and organic ligands with periodic building blocks, typically with adjustable porosity and high specific surface area. In recent years, the direct use of MOF materials as catalysts for electrocatalytic oxygen evolution reactions has attracted much attention, however, the MOF-based oxygen evolution electrocatalytic materials reported at present are still greatly limited due to the problems of poor electrical conductivity, material instability and the like of MOF materials. To overcome these limitations, most MOF materials are used as precursors or templates to derive various carbon-based metal compound materials by high temperature pyrolysis.

For example, chinese patent publication No. CN111584871A discloses a method for preparing a metal organic framework-derived iron sulfide @ carbon nanocomposite as a negative electrode material of a lithium ion battery, in which spindle-shaped MIL-88 nanoparticles are obtained by a hydrothermal reaction of fumaric acid and ferric nitrate, and the iron sulfide @ carbon nanocomposite with a carbon-coated and sulfur-doped core-shell structure can be obtained after sulfur doping and calcination. Further, for example, the Chinese patent publication No. CN111482189A discloses a method for preparing NiSe with a core-shell structure by using a metal-organic framework as a precursor₂The method for preparing the material for hydrogen evolution by adopting the electrocatalysis of @ NC comprises the steps of selectively selenizing a metal organic framework of a mixed ligand through a hydrothermal reaction, and then performing a calcination reaction through a one-step tubular furnace, thereby preparing a series of adjustable nitrogen-doped carbon-coated cubic phase core-shell nickel diselenide octahedral materials. However, the high temperature pyrolysis process can destroy the original structure of the MOF material, resulting in loss of organic ligands and agglomeration of metal nodes, which is not conducive to catalysis by the intrinsic advantageous properties of MOF itself.

Therefore, the development of a MOF material with universality and high activity for direct application in the field of electrocatalysis becomes a problem to be solved at present.

Disclosure of Invention

The invention aims to provide a transition metal doped nickel-based metal organic framework three-dimensional electrode material and a preparation method thereof.

The invention provides the following technical scheme:

a preparation method of a transition metal doped nickel-based metal organic framework three-dimensional electrode material comprises the following steps:

(1) preparing a three-dimensional conductive graphite substrate from a graphite sheet by an electrochemical stripping method;

(2) and (2) placing the three-dimensional conductive graphite substrate obtained in the step (1) in a mixed solution of a divalent nickel salt, a doped transition metal salt and terephthalic acid, and carrying out one-step hydrothermal reaction so as to in-situ grow a loaded transition metal doped nickel-based metal organic framework nanosheet array on the three-dimensional conductive graphite substrate, thereby obtaining the transition metal doped nickel-based metal organic framework three-dimensional electrode material.

In the process of preparing the transition metal (such as cerium) doped nickel-based metal organic framework three-dimensional electrode material, the transition metal (such as cerium) doped nickel-based metal organic framework three-dimensional electrode material is grown in situ on the three-dimensional graphite substrate by using a one-step hydrothermal reaction growth method, the obtained three-dimensional electrode material has a nanosheet array structure, more catalytic active sites can be exposed beneficially, the whole electronic structure of the MOF material can be optimized by doping transition metal (such as cerium), and the electrocatalytic activity of the nickel-based metal organic framework material is improved.

The transition metal salt is selected from cerium salt, iron salt, cobalt salt, copper salt, molybdenum salt, tungsten salt or chromium salt. Preferably, the transition metal salt is a cerium salt.

Preferably, in the step (1), the electrolyte is concentrated sulfuric acid, the electrochemical stripping condition is 5-10V direct current power supply, and the reaction time is 1-3 min.

Preferably, in the step (2), the temperature of the hydrothermal reaction is 140-160 ℃; the time of the hydrothermal reaction is 3-6 h. The structure of the generated transition metal doped nickel-based metal organic framework nanosheet array loaded on the three-dimensional graphite substrate is more regular under the temperature and time maintenance of the hydrothermal reaction. More preferably, the hydrothermal reaction time is 3 hours, so that the structure is further structured.

Preferably, in the step (2), the doping proportion of the transition metal salt is 1-12% of the divalent nickel salt, and the percentage is mole fraction. Further preferably, in the step (2), the doping proportion of the transition metal salt is 3-6% of the divalent nickel salt, and the percentage is a mole fraction. Under the mole fraction, the obtained transition metal doped nickel-based metal organic framework three-dimensional electrode material has the highest electrocatalytic activity in water electrolysis and oxygen evolution in alkaline electrolyte.

Taking cerium doping as an example, the preparation method of the cerium-doped nickel-based metal organic framework three-dimensional electrode material mainly comprises the following steps:

(1) preparing a three-dimensional graphite substrate: firstly, respectively carrying out ultrasonic cleaning and drying on a graphite flake by using acetone, ethanol and ultrapure water, then taking the graphite flake as a working electrode, a platinum sheet as a counter electrode and concentrated sulfuric acid as electrolyte, carrying out electrochemical oxidation stripping on the graphite flake under the action of direct-current voltage, and after the stripping is finished, cleaning and drying by using a large amount of ultrapure water to obtain a three-dimensional graphite substrate;

(2) preparing a cerium-doped nickel-based metal organic framework three-dimensional electrode material: adding nickel chloride hexahydrate, cerium nitrate hexahydrate and terephthalic acid into a mixed solvent of N, N-Dimethylformamide (DMF), ethanol and water, stirring for 20min to obtain a clear solution, then putting a three-dimensional graphite substrate into the solution, transferring the solution into a hydrothermal kettle, heating to 150 ℃, keeping for 3h, naturally cooling to room temperature, taking out an electrode material after the reaction is finished, washing with ethanol and ultrapure water for multiple times, and drying to obtain the cerium-doped nickel-based metal organic framework three-dimensional electrode material.

Specifically, in the step (1), the specific preparation method of the three-dimensional graphite substrate comprises the following steps: the method comprises the steps of ultrasonically cleaning a graphite flake for 20min by using acetone, ethanol and ultrapure water respectively, drying in a 60 ℃ oven for 4h, then taking the graphite flake as a working electrode, a platinum sheet as a counter electrode and concentrated sulfuric acid as electrolyte, carrying out electrochemical oxidation stripping on the graphite flake for 1min under the direct current voltage of 5V, cleaning by using a large amount of ultrapure water after stripping is finished, and drying in the 60 ℃ oven for 4h to obtain the three-dimensional graphite substrate.

Specifically, in the step (2), the specific preparation method of the hydrothermal solution is as follows: 119mg of nickel chloride hexahydrate, 2-26 mg of cerium nitrate hexahydrate and 116mg of terephthalic acid were weighed, followed by addition to DMF: ethanol: 16 parts of water: 1: in 1mL of the mixed solution, magnetic stirring was carried out for 20min to obtain a green clear solution.

The invention also provides the transition metal doped nickel-based metal organic framework three-dimensional electrode material prepared by the preparation method, and the transition metal doped nickel-based metal organic framework three-dimensional electrode material has a nanosheet array structure.

The invention also provides application of the transition metal doped nickel-based metal organic framework three-dimensional electrode material in water electrolysis and oxygen evolution in alkaline electrolyte.

The invention also discloses a cerium-doped nickel-based metal organic framework three-dimensional electrode material prepared by the preparation method, and the composite catalytic material has a nanosheet array structure.

The invention also discloses application of the cerium-doped nickel-based metal organic framework three-dimensional electrode material in electrolysis of water in alkaline electrolyte for oxygen evolution.

The method for testing the performance of the cerium-doped nickel-based metal organic framework three-dimensional electrode material for the electrocatalysis water decomposition oxygen analysis comprises the following steps: a three-electrode system is used, a working electrode is a cerium-doped nickel-based metal organic framework three-dimensional electrode material, a counter electrode is a carbon rod, a reference electrode is a saturated silver/silver chloride electrode, and an electrolyte is alkaline 1.0M potassium hydroxide solution.

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

(1) the invention prepares a novel electrolytic water anode catalytic electrode material, and a transition metal doped nickel-based metal organic framework nanosheet array grows in situ on a three-dimensional conductive graphite substrate, so that the conductivity of the MOF material is increased, the catalytic reaction resistance is reduced, and the overpotential is reduced;

(2) the catalytic electrode material provided by the invention has a transition metal doped nickel-based metal organic framework structure, wherein the electronic structure of the nickel-based metal organic framework material can be optimized by doping the transition metal, so that the electrocatalytic oxygen evolution reaction is facilitated;

(3) the transition metal doped nickel-based metal organic framework electrode material provided by the invention has good electrocatalytic oxygen evolution activity and stability under an alkaline condition.

Drawings

FIG. 1 is a SEM image of a cerium-doped nickel-based metal organic framework three-dimensional electrode material obtained in example 1, wherein the magnification is 1000 times;

FIG. 2 is a TEM image of the three-dimensional electrode material of the cerium-doped Ni-based metal-organic framework obtained in example 1, with a magnification of 200000;

FIG. 3 is an X-ray diffraction pattern of the cerium-doped nickel-based metal organic framework three-dimensional electrode material obtained in example 1, wherein the abscissa is twice the diffraction angle (2 θ) and the ordinate is the diffraction peak intensity;

FIG. 4 is a polarization curve diagram of the electrolytic water oxygen evolution reaction of the three-dimensional graphite substrate material, the nickel-based metal organic framework material and the cerium-doped nickel-based metal organic framework three-dimensional electrode material obtained in example 1 in a 1.0M KOH solution, wherein the scanning rate is 5 mV/s;

FIG. 5 is a graph showing the voltage variation with time under constant current in the oxidation reaction of electrolyzed water in a 1.0M KOH solution of the cerium-doped nickel-based metal organic framework three-dimensional electrode material obtained in example 1.

Detailed Description

The invention is further described with reference to specific embodiments and figures, which are not intended to limit the scope of the invention.

Example 1

(1) Preparation of three-dimensional conductive graphite substrate

Carrying out ultrasonic cleaning on a graphite flake for 20min by using acetone, ethanol and ultrapure water respectively, drying in a 60 ℃ oven for 4h, then taking the graphite flake as a working electrode, a platinum sheet as a counter electrode and concentrated sulfuric acid as electrolyte, carrying out electrochemical oxidation stripping on the graphite flake for 1min under the direct current voltage of 5V, cleaning by using a large amount of ultrapure water after stripping is finished, and drying in the 60 ℃ oven for 4h to obtain a three-dimensional graphite substrate;

(2) preparation of cerium-doped nickel-based metal organic framework three-dimensional electrode material

Respectively measuring 16mL of DMDMMF, 1mL of ethanol and 1mL of ultrapure water as a mixed solvent, then weighing 119mg of nickel chloride hexahydrate, 6.5mg of cerium nitrate hexahydrate and 116mg of terephthalic acid, adding into the mixed solvent, and stirring for 20min at normal temperature until the components are completely dissolved to obtain a green clear solution;

and (2) putting the prepared three-dimensional graphite substrate prepared in the step (1) into the solution, transferring the solution into a hydrothermal kettle, heating to 150 ℃, keeping the temperature for 3h, naturally cooling to room temperature, taking out the material after the reaction is finished, washing the material with ethanol and water for multiple times, and drying the material in a 60 ℃ drying oven for 4h to obtain the cerium-doped nickel-based metal organic framework three-dimensional electrode material (Ce-NiBDC/OG).

Fig. 1 is a scanning electron microscope SEM image of the cerium-doped nickel-based metal organic framework three-dimensional electrode material prepared in this embodiment, and it can be known from fig. 1 that the obtained catalytic electrode material has a nanosheet array structure.

Fig. 2 is a TEM image of a transmission electron microscope of the three-dimensional electrode material of the cerium-doped nickel-based metal organic framework prepared in this embodiment, and as can be seen from fig. 2, the lateral size of the nanosheet is about 500 nm.

Fig. 3 is an X-ray diffraction pattern of the cerium-doped nickel-based metal organic framework three-dimensional electrode material prepared in this example, and as can be seen from fig. 3, the cerium-doped nickel-based metal organic framework three-dimensional electrode material shows obvious diffraction peaks at positions of 8.7 °, 15.1 °, 16.0 ° and 17.2 °, and the diffraction peaks are consistent with the characteristic peak positions of the nickel-based metal organic framework material obtained by fitting, which proves that the cerium-doped nickel-based metal organic framework three-dimensional electrode material is a cerium-doped nickel-based metal organic framework three-dimensional electrode material.

Performing electrocatalysis water decomposition oxygen analysis performance test on the prepared three-dimensional graphite substrate (OG), nickel metal organic framework (NiBDC/OG) and cerium-doped nickel-based metal organic framework three-dimensional electrode material (Ce-NiBDC/OG), wherein the specific process comprises the following steps:

(1) a three-electrode system is used, wherein a working electrode is a three-dimensional graphite substrate, a nickel metal organic framework and a cerium-doped nickel-based metal organic framework three-dimensional electrode material, a counter electrode is a carbon rod, a reference electrode is a saturated silver/silver chloride electrode, and an electrolyte is a 1.0M KOH solution;

(2) CV activation: and (3) using an electrochemical workstation of CHI 660E in Shanghai, China, and adopting a CV program, wherein the test interval is 1.2-1.8V vs.RHE, the sweeping speed is 50mV/s, the electrode is circulated for 20 circles, and the electrode reaches a stable state.

And after activation, switching a program into a Linear Sweep Voltammetry (LSV) program, and carrying out LSV test, wherein the test interval is 1.2-1.8V vs. RHE, and the sweep speed is 5 mV/s.

FIG. 4 is a polarization curve diagram of the obtained three-dimensional graphite substrate, nickel metal organic framework and cerium-doped nickel-based metal organic framework three-dimensional electrode material in an electrolytic water oxygen evolution reaction in a 1.0M KOH solution, and it can be seen from FIG. 4 that the oxygen evolution overpotential in an alkaline electrolyte is only 265mV (the overpotential is 0V and 10mA cm relative to a reversible hydrogen electrode)^-2The difference in the measured potential).

After the electrode activation, the procedure was switched to the ISTEP procedure, and the stability test was performed with the current set at 0.01A and the time set at 10 h.

FIG. 5 is a graph showing the voltage change with time of the cerium-doped nickel-based metal organic framework three-dimensional electrode material prepared in this example in a 1.0M KOH electrolyte under a constant current test condition, and it can be seen from the graph that the current density is 10mA cm^-2The catalytic reaction is maintained for 10 hours, the voltage does not change greatly with time, and the excellent catalytic stability is shown.

Example 2

The preparation process as in example 1 is followed with the difference that: in the step (2), the dosage of the cerium nitrate hexahydrate is 2mg, and the cerium-doped nickel-based metal organic framework three-dimensional electrode material is prepared.

The prepared cerium-doped nickel-based metal organic framework three-dimensional electrode material shows over potential of 293mV in alkaline electrolyte.

Example 3

The preparation process as in example 1 is followed with the difference that: and (3) using 13mg of the cerous nitrate hydrate in the step (2) to prepare the cerium-doped nickel-based metal organic framework three-dimensional electrode material.

The prepared cerium-doped nickel-based metal organic framework three-dimensional electrode material shows an over potential of 280mV in alkaline electrolyte.

Example 4

The preparation process as in example 1 is followed with the difference that: in the step (2), the dosage of the cerous nitrate hexahydrate is 26mg, and the cerium-doped nickel-based metal organic framework three-dimensional electrode material is prepared.

The prepared cerium-doped nickel-based metal organic framework three-dimensional electrode material shows over-potential of 287mV in alkaline electrolyte.

Example 5

The preparation process as in example 1 is followed with the difference that: and (3) replacing 6.5mg of cerous nitrate hexahydrate by 4mg of ferric chloride hexahydrate in the step (2) to prepare the iron-doped nickel-based metal organic framework three-dimensional electrode material.

The prepared iron-doped nickel-based metal organic framework three-dimensional electrode material shows an overpotential of 290mV in alkaline electrolyte.

Example 6

The preparation process as in example 1 is followed with the difference that: and (3) replacing 6.5mg of cerous nitrate hexahydrate by 4mg of cobalt chloride hexahydrate in the step (2) to prepare the cobalt-doped nickel-based metal organic framework three-dimensional electrode material.

The prepared cobalt-doped nickel-based metal organic framework three-dimensional electrode material shows an overpotential of 305mV in an alkaline electrolyte.

The above-mentioned embodiments are intended to illustrate the technical solutions and advantages of the present invention, and it should be understood that the above-mentioned embodiments are only the most preferred embodiments of the present invention, and are not intended to limit the present invention, and any modifications, additions, equivalents, etc. made within the scope of the principles of the present invention should be included in the scope of the present invention.