阅读说明：本技术 一种基于Mxene/石墨烯水凝胶电沉积制备镍基层状结构电催化剂的合成方法 (Synthesis method for preparing nickel-based layered electrocatalyst based on Mxene/graphene hydrogel electrodeposition ) 是由 史星伟 张亚娟 张锁江 于 2021-08-20 设计创作，主要内容包括：本发明公开了一种基于Mxene/石墨烯水凝胶电沉积制备镍基层状结构电催化剂的方法。该催化剂制备方法包括以下步骤：将MXene、氧化石墨烯(GO)和掺杂剂混合均匀,超声分散；将分散液装入水热釜中高温条件下反应,得到非金属元素掺杂层状MXene/RGO水凝胶；将水凝胶电沉积在金属基底上得到结构可控的三维纳米结构电催化剂。本发明构造了一种三维层状结构的复合材料,相较于传统的层状氢氧化物(LDH),MXene/RGO的加入为镍基层状金属氢氧化物(NiX-LDH)提供了成核位点。其独特的三维层状结构有利于暴露更多活性位点,易于氢的吸附与脱附,提升了电解水制氢效率。(The invention discloses a method for preparing a nickel-based layered electrocatalyst based on Mxene/graphene hydrogel electrodeposition. The preparation method of the catalyst comprises the following steps: mixing MXene, Graphene Oxide (GO) and a doping agent uniformly, and performing ultrasonic dispersion; the dispersion liquid is put into a hydrothermal kettle to react under the condition of high temperature, and the non-metal element doped layered MXene/RGO hydrogel is obtained; and electrodepositing the hydrogel on a metal substrate to obtain the three-dimensional nanostructure electrocatalyst with a controllable structure. The invention constructs a composite material with a three-dimensional layered structure, and compared with the traditional layered hydroxide (LDH), the addition of MXene/RGO provides nucleation sites for nickel-based layered metal hydroxide (NiX-LDH). The unique three-dimensional layered structure is beneficial to exposing more active sites, is easy for hydrogen adsorption and desorption, and improves the hydrogen production efficiency by electrolyzing water.)

1. A synthetic method for preparing a nickel-based layered structure electrocatalyst based on Mxene/graphene hydrogel electrodeposition is characterized by comprising the following steps: the nickel-based metal hydroxide/MXene/RGO water electrolysis hydrogen production catalyst consists of an MXene/RGO layered material and a three-dimensional layered nickel-based LDH nanosheet array growing on an MXene/RGO substrate, wherein the nickel-based LDH is binary NiX-LDH (X ═ Co, Fe, Al, Mn and Ti) or ternary NiXY-LDH (X ═ Co, Fe, Y ═ Al and Mn).

2. A synthetic method for preparing a nickel-based layered structure electrocatalyst based on Mxene/graphene hydrogel electrodeposition is characterized by comprising the following steps:

step 1: preparing a multilayer MXene;

step 2: preparing a few-layer MXene;

and step 3: synthesizing a doped MXene/RGO hydrogel;

and 4, step 4: the nickel-based layered structure electrocatalyst is prepared based on Mxene/graphene hydrogel electrodeposition.

3. The synthesis method for preparing the nickel-based layered electrocatalyst based on Mxene/graphene hydrogel electrodeposition according to claim 2, wherein the synthesis method comprises the following steps: in the preparation of the multilayer MXene in the step 1, MAX powder is added into hydrofluoric acid and stirred at a certain temperature, and then the mixture is centrifugally washed for many times and dried in vacuum to obtain multilayer MXene powder; wherein the MAX powder is Ti₃AlC₂、Ti₂AlC、TiNbAlC、V₂AlC、Nb₂AlC、Ti₃AlCN、Ti₃SiC₂、Ti₂SiC、TiNbSiC、V₂SiC、Nb₂SiC、Nb₄SiC₃、Ti₃One or more SiCN.

4. The synthesis method for preparing the nickel-based layered electrocatalyst based on Mxene/graphene hydrogel electrodeposition according to claim 3, wherein the synthesis method comprises the following steps: the mass fraction of hydrofluoric acid is 25-50%; the stirring temperature is 30-50 ℃, and the stirring time is 5-50 h; the vacuum drying temperature is 50-80 ℃, and the drying time is 3-20 h.

5. The synthesis method for preparing the nickel-based layered electrocatalyst based on Mxene/graphene hydrogel electrodeposition according to claim 2, wherein the synthesis method comprises the following steps: in the step 2, the obtained multilayer MXene powder is added into a dimethyl sulfoxide solution to be stirred, then centrifugal washing and vacuum drying are carried out, and finally grinding is carried out to obtain the small-layer or single-layer MXene.

6. The synthesis method for preparing the nickel-based layered electrocatalyst based on Mxene/graphene hydrogel electrodeposition according to claim 2, wherein the synthesis method comprises the following steps: and step 3, adding graphene oxide, few-layer MXene and a doping agent into deionized water, transferring the mixture to a polytetrafluoroethylene reaction kettle after ultrasonic dispersion, performing high-temperature reaction, performing centrifugal washing for many times, and performing vacuum drying to obtain the doped MXene/RGO hydrogel.

7. The synthesis method for preparing the nickel-based layered electrocatalyst based on Mxene/graphene hydrogel electrodeposition according to claim 6, wherein the synthesis method comprises the following steps: the graphene oxide can be prepared by one or more of a micro-mechanical stripping method, a chemical vapor deposition method, an oxidation-reduction method, a solvent stripping method and a solvothermal method; wherein the concentration of the graphene oxide is 0.05-1.5 g/L; the concentration of MXene in the single layer or few layers is 1.0-5.0 g/L.

8. The synthesis method for preparing the nickel-based layered electrocatalyst based on Mxene/graphene hydrogel electrodeposition according to claim 6, wherein the synthesis method comprises the following steps: the doping agent used in the doped Mxene/graphene can be nitrogen source urea, melamine, amino acid, amide and amine; sulfur source toluene sulfonic acid, thioacetamide, cysteine; one or more of phosphorus source sodium hypophosphite, triphenylphosphine and phytic acid.

9. The synthesis method for preparing the nickel-based layered electrocatalyst based on Mxene/graphene hydrogel electrodeposition according to claim 6, wherein the synthesis method comprises the following steps: in the hydrothermal reaction, the nitrogen, sulfur and phosphorus doping hydrothermal temperature is 100-200 ℃, and the reaction time is 3-24 h.

10. The synthesis method for preparing the nickel-based layered electrocatalyst based on Mxene/graphene hydrogel electrodeposition according to claim 2, wherein the synthesis method comprises the following steps: in the step 4, the concentration of the metal salt is 1-5 mmol.

Technical Field

The invention relates to the field of preparation of catalysts for hydrogen evolution by electrolysis of water, and relates to a synthesis method for preparing a nickel-based layered electrocatalyst based on Mxene/graphene hydrogel electrodeposition.

Background

In recent years, energy crisis and environmental issues are the two most important topics being discussed. The excessive consumption of conventional fossil fuels causes severe problems such as environmental pollution and global warming. Therefore, there is an urgent need to develop renewable and clean alternative energy sources to maintain social and ecological environmental coordination and sustainable development. Among them, hydrogen is attracting attention because of its advantages such as being renewable, free from greenhouse gas emission, and high in energy density. The hydrogen production method by water electrolysis is a simple pollution-free hydrogen production method at present, and is an ideal way for obtaining hydrogen energy. In addition, the hydrogen generation and decomposition processes are mutually inverse processes, so that the hydrogen source is ensured not to be supplied in an outage way. Therefore, hydrogen energy can be obtained as long as a certain amount of electric energy is supplied.

However, in the process of hydrogen production by water electrolysis, the problems of low hydrogen production efficiency, high production cost and the like are always faced, which directly results in that less than 5% of hydrogen energy in the market comes from the water electrolysis method, so that the development of a stable and low-cost efficient electrode material is an effective solution.

MXene is a novel transition metal carbide or nitride, has the characteristics of unique two-dimensional structure, good stability, ultrahigh conductivity, excellent specific capacitance and the like, and therefore has great application prospects in the aspects of capacitors, catalysis, chemical adsorption and the like. In addition, the surface of MXene is rich in-OH, -F, -O and other active chemical functional groups, a three-dimensional layered structure is expected to be formed by self-assembly of graphene and a hydrothermal method, the dispersibility, the structural stability and the conductivity of the MXene are improved, and a good carrier is provided for the transition metal hydroxide.

Disclosure of Invention

Aiming at the problems of complex preparation process, low catalytic activity, poor stability and the like of the existing hydrogen production catalyst, the invention provides a synthetic method for preparing a nickel-based layered electrocatalyst based on Mxene/graphene hydrogel electrodeposition. The hydrogen evolution catalyst prepared by the invention has a three-dimensional layered structure, a large specific surface area and abundant catalytic active sites, can realize high-efficiency hydrogen evolution in alkaline electrolyte, and has good chemical stability.

In order to achieve the purpose of the invention, the invention adopts the technical scheme that:

step 1: adding MAX powder into hydrofluoric acid, stirring at a certain temperature, centrifuging for many times, washing and drying in vacuum to obtain multilayer MXene powder;

the MAX powder comprises: ti₃AlC₂、Ti₂AlC、TiNbAlC、V₂AlC、Nb₂AlC、Ti₃AlCN、Ti₃SiC₂、Ti₂SiC、TiNbSiC、V₂SiC、Nb₂SiC、Nb₄SiC₃、Ti₃One or more of SiCN;

the mass fraction of the hydrofluoric acid is 25-50%;

the stirring temperature is 30-50 ℃, and the stirring time is 5-50 h;

the vacuum drying temperature is 50-80 ℃, and the drying time is 3-20 h.

Step 2: adding the multilayer MXene powder into dimethyl sulfoxide, stirring, centrifugally washing, vacuum drying, and finally grinding to obtain single-layer or few-layer MXene;

and step 3: adding graphene oxide, single-layer or few-layer MXene and a doping agent into deionized water, transferring the mixture to a polytetrafluoroethylene reaction kettle after ultrasonic dispersion, performing high-temperature reaction, performing centrifugal washing for many times and performing vacuum drying to obtain a doped MXene/RGO hydrogel;

the graphene oxide can be prepared by one or more of a micro-mechanical stripping method, a chemical vapor deposition method, an oxidation-reduction method, a solvent stripping method and a solvothermal method.

The doping agent comprises nitrogen source urea, melamine, amino acid, amide and amine; sulfur source toluene sulfonic acid, thioacetamide, cysteine; one or more of phosphorus source sodium hypophosphite, triphenylphosphine and phytic acid.

The concentration of the graphene oxide is 0.05-1 g/L;

the concentration of the single-layer or few-layer MXene is 1.0-5.0 g/L;

in the hydrothermal reaction, the nitrogen, sulfur and phosphorus doping hydrothermal temperature is 100-200 ℃, and the reaction time is 3-24 h.

And 4, step 4: uniformly mixing and mixing metal salt particles and doped MXene/RGO hydrogel, ultrasonically dispersing, and depositing metal ions at different scanning turns by using cyclic voltammetry on a nickel net as a substrate in a three-electrode system to obtain the nickel-based layered structure-Mxene/graphene hydrogel electrocatalyst.

The concentration of the metal salt is 1-5 mmol;

drawings

FIG. 1 is a precursor Ti₃AlC₂；

FIG. 2 is an electron micrograph of a multilayer titanium carbide powder;

FIG. 3 is an electron micrograph of single or few layers of titanium carbide powder;

FIG. 4 is an electron micrograph of NiFe-LDH/N-MXene/RGO;

FIG. 5 is an electron micrograph of NiFe-LDH/S-MXene/RGO;

FIG. 6 is an electron micrograph of NiFe-LDH/P-MXene/RGO

FIG. 7 is a polarization curve for NF, MXene, NiFe-LDH/MXene/RGO materials.

Detailed Description

Various exemplary embodiments of the present invention will now be described in detail to make the objects, technical solutions and advantages of the present invention more apparent. This detailed description is not to be taken in a limiting sense, but is to be understood as a more detailed description of certain aspects, features and embodiments of the invention.

Example 1

A synthetic method for preparing a nickel-based layered structure electrocatalyst based on Mxene/graphene hydrogel electrodeposition comprises the following steps:

step 1: the MAX powder was added to hydrofluoric acid with stirring, then washed by centrifugation and dried in vacuum.

Step 2: adding the multi-layer MXene powder into dimethyl sulfoxide, stirring, centrifugally washing, vacuum drying, and finally grinding to obtain a few layers or a single layer of MXene;

and step 3: adding graphene oxide, few-layer MXene and urea serving as nitrogen sources into 20mL of deionized water, ultrasonically dispersing, transferring into a polytetrafluoroethylene reaction kettle, reacting for 5 hours at 160 ℃, centrifuging and washing for multiple times, and vacuum drying to obtain nitrogen-doped MXene/RGO hydrogel;

and 4, step 4: the metal salt particles and the doped MXene/RGO hydrogel are uniformly mixed, ultrasonically dispersed, and deposited with metal ions at different scanning cycles by a cyclic voltammetry method by taking a nickel mesh as a substrate in a three-electrode system.

In step 1, the MAX is 1g Ti₃AlC₂；

In the step 1, the consumption of the hydrofluoric acid is 30mL, and the mass fraction is 45%;

in the step 1, the stirring temperature is 35 ℃, and the stirring time is 45 hours;

in the steps 1 and 2, the vacuum drying temperature is 60 ℃, and the drying time is 24 hours;

in the step 3, the concentration of the graphene oxide is 0.2 g/L;

the concentration of MXene in the step 3 is 1 g/L;

the mass of the urea in the step 3 is 0.1073 g;

in the step 4, the metal salt particles are nickel nitrate hexahydrate and ferric nitrate nonahydrate respectively, and the molar mass ratio is 1: 1 mmol.

Example 2

This example is the same as example 1, except for the following parameters:

in step 1, the MAX is 0.5g Ti₂AlC；

In the step 1, the consumption of the hydrofluoric acid is 25mL, and the mass fraction is 35%;

in the step 1, the stirring temperature is 45 ℃, and the stirring time is 35 hours;

in the step 3, the concentration of the graphene oxide is 0.45 g/L;

the concentration of MXene in the step 3 is 1.2 g/L;

in the step 3, the urea is changed into p-toluenesulfonic acid as a sulfur source, the mass is 0.2691g, the reaction temperature is 160 ℃, and the reaction time is 8 h;

in the step 4, the metal salt particles are nickel nitrate hexahydrate and ferric nitrate nonahydrate respectively, and the molar mass ratio is 2: 3 mmol.

Example 3

This example is the same as example 1, except for the following parameters:

in step 1, the MAX is 0.5g Ti₃SiC₂；

In the step 1, the consumption of the hydrofluoric acid is 35mL, and the mass fraction is 25%;

in the step 1, the stirring temperature is 30 ℃, and the stirring time is 25 hours;

in the step 3, the concentration of the graphene oxide is 1 g/L;

the concentration of MXene in the step 3 is 1.5 g/L;

in the step 3, the urea is changed into phytic acid serving as a phosphorus source, the mass is 0.1774g, the reaction temperature is 170 ℃, and the reaction time is 12 hours.

In the step 4, the metal salt particles are nickel nitrate hexahydrate and ferric nitrate nonahydrate respectively, and the molar mass ratio of the metal salt particles is 4: 1mmol of the active component;

compared with the traditional layered hydroxide, MXene/RGO provides nucleation sites for LDH. The unique three-dimensional layered structure is beneficial to exposing rich active sites, is beneficial to the adsorption and desorption of hydrogen, and can realize high-efficiency hydrogen evolution.