CN114059093A

CN114059093A - Zn-doped CoP @ MXene/NF composite material and synthesis method and application thereof

Info

Publication number: CN114059093A
Application number: CN202111362180.4A
Authority: CN
Inventors: 蒋继波; 孙冉; 黄星; 许文秀; 魏影; 周少博; 李明晶; 李雨露; 陈晓敏; 李婷婷; 宣宇娜; 韩生
Original assignee: Shanghai Institute of Technology
Current assignee: Shanghai Institute of Technology
Priority date: 2021-11-17
Filing date: 2021-11-17
Publication date: 2022-02-18
Anticipated expiration: 2041-11-17
Also published as: CN114059093B

Abstract

The invention relates to a Zn-doped CoP @ MXene/NF composite material and a synthesis method and application thereof, wherein the composite material is prepared by the following steps: dispersing inorganic salt in strong acid, adding titanium aluminum carbide, etching, then adding water, centrifuging and drying to obtain MXene, dispersing the MXene in the water to obtain a colloidal solution, soaking foamed nickel in the colloidal solution, and drying to obtain an MXene/NF composite material; soaking the MXene/NF composite material in a mixed solution containing a promoter and a cobalt source, reacting, washing and drying to obtain a Co-MOF @ MXene/NF composite material, soaking the composite material in an ethanol water solution containing a zinc source, reacting, washing and drying to obtain a ZnCo-LDH @ MXene/NF composite material; and (3) carrying out a separated gas phosphating reaction on the ZnCo-LDH @ MXene/NF composite material to obtain the target product. Compared with the prior art, the composite material has excellent HER performance and OER performance, low cost and difficult shedding.

Description

Zn-doped CoP @ MXene/NF composite material and synthesis method and application thereof

Technical Field

The invention belongs to the technical field of integral water decomposition, and relates to a Zn-doped CoP @ MXene/NF composite material and a synthesis method and application thereof.

Background

Climate change and energy crisis are receiving increasing attention, and there has been a great deal of research into alternative energy storage and conversion systems. Due to the characteristics of sustainability and eco-friendliness, hydrogen energy is expected to become a main source of future energy supply. Water-splitting electrolysis is considered to be an effective technique for producing hydrogen. Typically, the water splitting reaction involves two half-reactions: hydrogen Evolution Reaction (HER) and Oxygen Evolution Reaction (OER). The platinum-based material in the noble metal-based material is a benchmark catalyst for reducing the overpotential of HER, and the iridium-based or ruthenium-based material is a benchmark catalyst for reducing the overpotential of OER. However, the high cost and scarcity severely limit its large-scale application. Therefore, for HER and OER, it is urgent to search for a catalyst having excellent activity and durability, low cost, and sufficient raw material reserves.

Transition metal carbides, sulfides, phosphides, nitrides and like compounds have been developed to replace noble metal-based materials. Wherein, it is prepared byTransition metal-based phosphides (TMPs), e.g. FeP, CoP, Ni₂P、Cu₃P, ZnP and WP, have been extensively studied due to their non-noble metal nature and their unique activity on HER. Among them, cobalt-based phosphide, nickel-based phosphide and iron-based phosphide exhibit electrocatalytic activity for OER in addition to catalytic activity for HER. Therefore, the bifunctional electrocatalyst developed by taking TMPs as the material has an application prospect, can work in the same electrolyte, and has lower cost. However, the electrocatalytic properties of TMPs are still far from satisfactory due to the inherently poor electrical conductivity of TMPs.

MXenes is a new two-dimensional (2D) family based on transition metal carbides or nitrides, and due to its excellent electrical and metallic conductivity properties, it attracts more and more attention and is one of the focuses in the field of electrochemical energy storage and conversion. MXenes have good surface hydrophilicity and mechanical stability, simultaneously have a high active surface and are easy to adjust, and can be used for overall water decomposition. Therefore, it is very desirable to couple MXenes with bifunctional active catalysts to improve HER and OER activities, however, reports on MXenes-based heterostructures as effective bifunctional electrocatalysts for bulk water splitting are very limited, studies on compounding MXenes with TMPs for bulk water splitting have not been reported, and development of a catalyst with excellent HER and OER activities based on MXenes and TMPs is challenging.

The use of a catalyst in powder form for electrocatalysis requires the deposition of the powdered catalyst on the electrode by the addition of a binder such as polyvinylidene fluoride (PVDF) or Nafion. And the binder greatly hinders the contact between the electrocatalyst and the electrolyte, thereby reducing the catalytic activity of the catalyst. In addition, the powdered catalyst may be detached from the electrode during the electrochemical process, resulting in poor catalytic performance.

Disclosure of Invention

The invention aims to provide a Zn-doped CoP @ MXene/NF composite material and a synthesis method and application thereof, so as to overcome the defects of poor integral water decomposition capability, high cost, limited catalytic activity of a powder catalyst, easy shedding and the like of a bifunctional catalyst in the prior art.

The purpose of the invention can be realized by the following technical scheme:

one of the technical schemes of the invention provides a synthesis method of a Zn-coped CoP @ MXene/NF composite material, which comprises the following steps:

(1) dispersing inorganic salt in strong acid, adding titanium aluminum carbide, etching, adding water, centrifuging for many times, and drying to obtain MXene;

(2) dispersing the obtained MXene in water to obtain MXene colloidal solution, soaking the foamed nickel into the MXene colloidal solution, and drying to obtain MXene/NF composite material;

(3) mixing a promoter and a cobalt source to obtain a mixed solution, soaking the MXene/NF composite material in the mixed solution, and reacting, washing and drying to obtain a Co-MOF @ MXene/NF composite material;

(4) soaking the obtained Co-MOF @ MXene/NF composite material into an ethanol water solution containing a zinc source, and reacting, washing and drying to obtain a ZnCo-LDH @ MXene/NF composite material;

(5) and (3) carrying out a separation type gas phosphating reaction on the obtained ZnCo-LDH @ MXene/NF composite material to obtain a target product.

Further, in the step (1), the inorganic salt is lithium fluoride, and the strong acid is hydrochloric acid.

Furthermore, the concentration of the hydrochloric acid is 9M, and the adding amount ratio of the lithium fluoride, the hydrochloric acid and the titanium aluminum carbide is 1.6g:20mL:1 g.

Further, in the step (1), the etching temperature is 20-40 ℃, and the etching time is 20-30 hours.

Further, in the step (1), the specific steps of multiple centrifugations are as follows:

(1) after adding water, centrifuging twice, and discarding supernatant obtained by each centrifugation; centrifuging for three times, and collecting supernatant obtained by each centrifugation to obtain single-layer or multi-layer MXene aqueous suspension;

(2) the resulting aqueous MXene suspension was purged with nitrogen, and the precipitate was collected by centrifugation, thereby completing the centrifugation.

Furthermore, in the step (1), the centrifugal rotating speed is 3000r/min, and the centrifugal time is 5-10min each time.

Furthermore, in the step (2), nitrogen is continuously introduced for 30 min.

Furthermore, in the step (2), the centrifugal speed is 10000r/min, and the centrifugal time is 30 min.

Further, MXene was obtained by centrifugation and freeze-drying in step (1).

Further, in the step (2), the concentration of the MXene colloidal solution is 1-4 mg/mL.

Furthermore, in the step (2), the soaking time of the foamed nickel in the MXene colloidal solution is 1-3 h.

Further, in the step (3), the promoter is 0.4M 2-methylimidazole aqueous solution, the cobalt source is 50mM cobalt nitrate hexahydrate aqueous solution, the size of the MXene/NF composite material is 1cm by 2cm by 2.5mM, and the amount of the 2-methylimidazole aqueous solution and the cobalt nitrate hexahydrate aqueous solution added is 40mL and 40mL respectively.

Furthermore, in the step (3), the reaction time is 3-5 h.

Further, in the step (3), washing is performed using water.

Further, in the step (4), the zinc source is zinc nitrate hexahydrate, and the volume ratio of ethanol to water in the ethanol aqueous solution is 1: 4, the size of the Co-MOF @ MXene/NF composite material is 1cm by 2cm by 2.5mm, and the amount of zinc nitrate hexahydrate and the amount of an ethanol water solution which are added correspondingly are 0.5mmol and 100mL respectively.

Furthermore, in the step (4), the reaction temperature is 60-90 ℃ and the reaction time is 10-20 min.

Further, in the step (2), the drying temperature is 60 ℃, and the drying time is 12 h.

Further, in the step (2), the foamed nickel is pretreated before being added, and the pretreatment process is as follows:

shearing a foam nickel substrate into a sample with the required size, soaking the sample in hydrochloric acid, performing ultrasonic treatment by using acetone, performing cyclic ultrasonic treatment by using ethanol and water for several times, and finally performing vacuum drying overnight.

Furthermore, the concentration of the hydrochloric acid is 3M, and the soaking time in the hydrochloric acid solution is 30 min.

Further, the sonication time in acetone was 15 min.

Further, the temperature for vacuum drying was 60 ℃.

Further, in the step (4), washing is repeated using ethanol and water.

Further, in the step (4), the drying temperature is 60 ℃.

Further, in the step (5), the phosphating agent used in the separated gas phosphating reaction is NaH₂PO₂And (3) powder.

Further, the ZnCo-LDH @ MXene/NF composite material and NaH₂PO₂The mass ratio of the powder is 1: 20.

further, in the step (5), in the separated gas phosphating reaction, the annealing temperature is 100-350 ℃, the heat preservation time is 2 hours, and the heating rate is 1-3 ℃/min.

Further, in the step (5), the flow rate of the inert gas is 300sccm during the separated gas phosphating reaction.

Further, the inert gas is nitrogen.

The second technical scheme of the invention provides a Zn-coped CoP @ MXene/NF composite material, and the composite material is prepared by the synthesis method.

Further, the composite material comprises Zn-CoP nanosheets, MXene substrates and foamed nickel, wherein the MXene substrates are attached to the foamed nickel, and the Zn-CoP nanosheets are attached to the MXene substrates.

Furthermore, the Zn-CoP nanosheets are hollow, and the Zn-CoP nanosheet array is distributed on the MXene substrate.

The third technical scheme of the invention provides the application of the composite material, and the composite material can be applied to electrocatalytic integral water decomposition reaction, and is particularly suitable for electrocatalytic integral water decomposition in an alkaline solution.

Further, when the composite material is used for electrocatalytic bulk water splitting reaction, the composite material is used as a working electrode in the electrocatalytic bulk water splitting reaction, potassium hydroxide solution without air is used as electrolyte, an Ag/AgCl electrode is used as a reference electrode, and a platinum wire electrode is used as a counter electrode, and the method specifically comprises the following steps:

connecting the Zn-doped CoP @ MXene/NF composite material, an Ag/AgCl electrode and a platinum wire electrode with an electrochemical workstation, and testing the electrocatalytic performance of the Zn-doped CoP @ MXene/NF composite material in a potassium hydroxide solution.

Further, the concentration of the potassium hydroxide solution was 1.0M.

Further, nitrogen gas was introduced into the potassium hydroxide solution to drive off air in the potassium hydroxide solution, thereby obtaining an air-free potassium hydroxide solution.

Further, the nitrogen gas was introduced for 30 minutes.

Furthermore, before the Zn-doped CoP @ MXene/NF composite material is used, the surface of the Zn-doped CoP @ MXene/NF composite material is cleaned by the potassium hydroxide solution.

The cobalt source can provide Co for the generation of target products²⁺Co-MOF into Zn (NO)₃)₂·6H₂In O solution, water dissolves to produce H⁺And OH^-，H⁺Promoting Co-MOF etching to produce Co²⁺，OH^-Promoting Zn⁶⁺，Co²⁺Precipitating to form ZnCo-LDH, and completely etching the Co-MOF along with the hydrolysis to form a hollow nano array structure with small nano sheets growing on the surface. After Zn is doped, the P-position 3P orbit moves upwards, so that the filling reverse bond state of the H1s orbit is reduced, the H-P bond is enhanced, and the composite material and the H are promoted₂O, increasing the HER performance of the material. Meanwhile, Zn-CoP can be converted into CoOOH in situ in the reaction process, so that the OER performance of the composite material is enhanced.

In the Zn-doped CoP @ MXene/NF composite material, the Zn-doped CoP grows on an MXene/NF substrate to form a layered 3D porous structure with large specific surface area and high conductivity. The foam nickel is used as sound absorption porous metal with three-dimensional full-through mesh structure and excellent performance, the nickel framework is hollow and is mutually connected in a metallurgical state, and the sound absorption porous metal has the advantages of good stability, high porosity, thermal shock resistance, small bulk density, large specific surface area and the like, more importantly, an adhesive additive can be avoided, the contact capacity of the composite material and water is further improved, and the catalyst can fully exert catalytic activity; the MXene prepared by etching the MAX phase has good conductivity and hydrophilicity, large surface area and adjustable structure. The Zn-doped CoP @ MXene/NF composite material shows excellent adsorption capacity on a hydrogen intermediate in an alkaline solution, so that the Zn-doped CoP @ MXene/NF composite material has excellent catalytic performance, hydrogen is easier to prepare, oxygen adsorption and desorption can be promoted, and the Zn-doped CoP @ MXene/NF composite material has excellent integral water decomposition capacity.

The invention prepares the high-performance catalyst through the design of a nano/microstructure, the preparation process is simple, and the prepared Zn-doped CoP @ MXene/NF composite material has a hollow and porous structure. In the composite material, hollow Zn-CoP nano arrays grow on NF loading MXene substrates, are derived from Metal Organic Framework (MOF) precursors, and can be directly used as a high-activity and durable hydrogen evolution electrocatalyst. The Zn-CoP array can also be converted into Zn-CoOOH in situ, with enhanced OER performance. The Zn-CoP array reduces energy barrier through Zn doping, promotes electrolyte permeation and promotes release of precipitated bubbles, thereby ensuring high conductivity of the composite material.

The Zn-doped CoP in the composite material is combined with the natural conductive material MXene to form strong synergistic chemical and electronic coupling, and the Zn doping modifies the electronic structure of the composite material so as to exert the advantages and functions of the catalyst components to the maximum extent. The composite material can be used as an anode and a cathode to realize high-efficiency integral water decomposition reaction.

During the preparation of MXene, Al atoms are selectively removed by multiple times of centrifugation to obtain single-layer or multi-layer MXene aqueous suspension. The Zn-CoP is obtained by phosphorization under the inert gas atmosphere through an annealing process. The invention limits the process conditions in the reaction process, such as annealing temperature, heating rate and the like, and can obtain products with better crystallinity in a limited range, namely the performance of the products can reach the optimum.

Compared with the prior art, the invention has the following advantages:

(1) the Zn-doped CoP @ MXene/NF composite material provided by the invention has good HER performance and OER performance, and has the advantages of low energy barrier required to be broken through for hydrogen evolution and oxygen evolution, high conversion rate and high speed;

(2) compared with most catalysts, the Zn-doped CoP @ MXene/NF composite material has lower synthesis cost, catalyst raw materials can be purchased, the earth reserve is sufficient, and the Zn-doped CoP @ MXene/NF composite material does not relate to explosive and toxic drugs;

(3) in the Zn-doped CoP @ MXene/NF composite material, the MXene substrate is attached to the foamed nickel, and the Zn-CoP nanosheets are distributed on the MXene substrate, so that an adhesive is avoided, the contact capability of the composite material with water is further improved, the composite material is not easy to fall off, and the catalytic activity is fully exerted.

Drawings

FIG. 1 is a graph showing the comparison of HER overpotential performances of Zn-doped CoP @ MXene/NF composite materials, CoP @ MXene/NF composite materials and ZnCo-LDH @ MXene/NF obtained in example 1, comparative example 1 and comparative example 2, respectively;

FIG. 2 is a graph comparing the OER overpotential performance of Zn-doped CoP @ MXene/NF composite materials, CoP @ MXene/NF composite materials and ZnCo-LDH @ MXene/NF obtained in example 1, comparative example 1 and comparative example 2.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.

In the following examples, unless otherwise specified, all the conventional commercially available raw materials or conventional processing techniques in the art are indicated.

In the following examples, the nickel foam used was obtained from the Kunshan Wida electronics Co.

In the following examples, the pretreatment process of the nickel foam was as follows:

the foam nickel substrate was cut into test pieces with a size of 1cm x 2cm x 2.5mm, then soaked in 3M hydrochloric acid for 30min, followed by sonication with acetone for 15min, then subjected to cyclic sonication several times with ethanol and water, and finally vacuum dried at 60 ℃ overnight.

Example 1:

the raw materials for preparing the Zn-doped CoP @ MXene/NF composite material in the embodiment are as follows:

hydrochloric acid (9M, 20mL)

Lithium fluoride (1.6g)

Titanium carbide aluminium (1g)

2-Methylimidazole aqueous solution (0.4M, 40mL)

Aqueous cobalt nitrate hexahydrate (50mM, 40mL)

Zinc nitrate hexahydrate (0.5mmol)

Ethanol aqueous solution (volume ratio of ethanol to water 1: 4, 100mL)

Sodium hypophosphite

A Zn-coped CoP @ MXene/NF composite material is prepared by the following preparation method:

(a) hydrochloric acid (9M, 20mL), 1.6g lithium fluoride was added to a polypropylene (PP) rubber bottle and magnetically stirred for 5 minutes. Then, 1g of titanium aluminum carbide was slowly added thereto, and etching was performed for 24 hours under an oil bath condition at 35 ℃. After the etching was completed, 140ml of deionized water was added to the PP rubber bottle, which was then gently shaken and the contents were transferred to 4 centrifuge tubes and centrifuged at 3000r/min for 5 min. And discarding the supernatant obtained in the first two centrifugations, performing third, fourth and fifth centrifugations, and collecting the supernatant obtained after the third, fourth and fifth centrifugations to obtain single-layer or multi-layer MXene aqueous suspension. Then N is added₂Blowing into the collected MXene water suspension for 30min, centrifuging at 10000r/min for half an hour, collecting precipitate, and freeze drying to obtain MXene. When in use, MXene is dispersed in water to form MXene colloidal solution (4 mg/mL);

(b) soaking a piece of pretreated foamed nickel into MXene colloidal solution to enable the foamed nickel to be quickly adsorbed on the surface of the foamed nickel, taking out after 1 hour, and vacuum-drying at 60 ℃ for 12 hours to obtain an MXene/NF composite material;

(c) quickly pouring 2-methylimidazole aqueous solution (0.4M, 40mL) into cobalt nitrate hexahydrate aqueous solution (50mM, 50mL) to obtain mixed solution, then immersing a piece of MXene/NF composite material into the mixed solution, reacting for 4 hours, taking out a sample, washing with deionized water, and standing at 60 ℃ overnight to obtain a Co-MOF @ MXene/NF composite material;

(d) then preparing a ZnCo-LDH array on the Co-MOF @ MXene/NF composite material, immersing a piece of Co-MOF @ MXene/NF composite material into an ethanol water solution (the volume ratio of ethanol to water is 1: 4, 100mL) containing zinc nitrate hexahydrate (0.5mmol), reacting at 85 ℃ for 15 minutes, then removing the purple color of the Co-MOF, taking out a sample, repeatedly washing with ethanol and water, and drying at 60 ℃ to obtain the ZnCo-LDH @ MXene/NF composite material;

(e) and finally preparing a nano matrix Zn-CoP: one piece of ZnCo-LDH @ MXene/NF composite material and NaH₂PO₂The powder (with the mass being 20 times of that of the ZnCo-LDH @ MXene/NF composite material) is placed at two different positions of a ceramic boat, and NaH is adopted₂PO₂And (3) the mixture is positioned on the upstream side of the tubular furnace, the temperature is raised to 350 ℃ at the heating rate of 2 ℃/min under the nitrogen atmosphere, the heat preservation time is 2 hours, the nitrogen flow rate is 300sccm, and the target product Zn-doped CoP @ MXene/NF composite material is obtained after the reaction is finished.

The Zn-doped CoP @ MXene/NF composite material is directly used as a working electrode in electrocatalytic integral water decomposition reaction, and the method comprises the following specific steps:

(1) the Zn-doped CoP @ MXene/NF composite material is directly used as a working electrode in the electrocatalytic integral water decomposition reaction;

(2) preparing 1.0M potassium hydroxide solution as electrocatalysis electrolyte, introducing nitrogen to drive air away, taking Zn-coped CoP @ MXene/NF composite material, Ag/AgCl electrode and platinum wire electrode as working electrode, reference electrode and counter electrode respectively, connecting the working electrode, reference electrode and counter electrode to an electrochemical workstation, and measuring the electrocatalysis performance of the electrode material in the electrolyte.

The test results are shown in fig. 1 and fig. 2, respectively. As can be seen from FIG. 1, when the current density was 10mA/cm²When the hydrogen evolution overpotential of the Zn-doped CoP @ MXene/NF composite material is 142 mV; from FIG. 2, it can be seen thatWhen the current density is 10mA/cm²When the composite material is used, the oxygen evolution overpotential of the Zn-doped CoP @ MXene/NF composite material is 310 mV.

Example 2:

compared with example 1, most of them are the same except that in this example, the temperature is raised to 350 ℃ at a heating rate of 2 ℃/min instead to 100 ℃ at a heating rate of 1 ℃/min.

Example 3:

compared with example 1, most of them are the same except that in this example, the temperature is increased to 350 ℃ at a heating rate of 2 ℃/min instead to 200 ℃ at a heating rate of 3 ℃/min.

Example 4:

compared with example 1, most of them are the same except that in this example, etching was carried out for 24 hours under 35 ℃ oil bath condition, and etching was carried out for 20 hours under 20 ℃ oil bath condition.

Example 5:

compared with example 1, most of them are the same except that in this example, etching was carried out for 24 hours under 35 ℃ oil bath condition, instead of 30 hours under 40 ℃ oil bath condition.

Example 6:

compared with example 1, most of the parts are the same except that in the example, the MXene colloidal solution (4mg/mL) is changed to MXene colloidal solution (1 mg/mL).

Example 7:

compared with example 1, most of the parts are the same except that in the example, the MXene colloidal solution (4mg/mL) is changed to MXene colloidal solution (3 mg/mL).

Example 8:

compared with the embodiment 1, the most parts are the same, except that in the embodiment, the vacuum drying at 60 ℃ for 12h after taking out and placing for 1h is changed into the vacuum drying at 60 ℃ for 3h, and then the vacuum drying at 60 ℃ for 12h is taken out and placing for vacuum drying.

Example 9:

compared with the embodiment 1, the most parts are the same, except that in the embodiment, the vacuum drying at 60 ℃ for 12h after taking out and placing for 1h is changed into the vacuum drying at 60 ℃ for 12h after taking out and placing for vacuum drying at 60 ℃ for 12 h.

Example 10:

compared with example 1, the method is mostly the same, except that in this example, the reaction time in step (c) is changed to 3 hours after 4 hours.

Example 11:

compared with example 1, the method is mostly the same, except that in this example, the reaction time in step (c) is changed to 5 hours after 4 hours.

Example 12:

compared with example 1, most of them are the same except that in this example, the reaction at 85 ℃ for 15 minutes in step (d) is changed to the reaction at 60 ℃ for 10 minutes.

Example 13:

compared with example 1, most of them are the same except that in this example, the reaction at 85 ℃ for 15 minutes in step (d) is changed to a reaction at 90 ℃ for 20 minutes.

Comparative example 1:

compared to example 1, most of them are the same except that the addition of zinc nitrate hexahydrate is omitted, i.e. there is no doping of Zn.

Preparing raw materials of a CoP @ MXene/NF composite material:

hydrochloric acid (9M, 20mL)

Lithium fluoride (1.6g)

Titanium carbide aluminium (1g)

2-Methylimidazole aqueous solution (0.4M, 40mL)

Aqueous cobalt nitrate hexahydrate (50mM, 40mL)

0.5mmol of zinc nitrate hexahydrate

Sodium hypophosphite

A CoP @ MXene/NF composite material is prepared by the following preparation method:

(a) 20mL (9M) of hydrochloric acid, 1.6g of lithium fluoride, was added to a polypropylene rubber bottle and magnetically stirred for 5 minutes. Then 1g of titanium aluminum carbide was slowly added and etching was carried out for 24 hours under 35 ℃ oil bath conditions. After etching was complete, 140ml of deionized water was added to the PVP vial, and the vial was then gently shaken and transferred to 4 centrifuge tubes. Centrifuging at 3000r/min for 5min, discarding the supernatant of the first two centrifugations, performing the third, fourth and fifth centrifugations, and collecting the supernatant after the third, fourth and fifth centrifugations to obtain monolayer or multilayer Xene aqueous suspension. N2 was then blown into the collected aqueous MXene suspension for 30min, then centrifuged at 10000r/min for half an hour, the precipitate was collected and freeze dried. When in use, the material is dispersed in water to form a colloidal solution (4 mg/mL);

(b) then taking a piece of pretreated foamed nickel, immersing the piece of pretreated foamed nickel into MXene colloidal solution to enable the piece of pretreated foamed nickel to be quickly adsorbed on the surface of the foamed nickel, taking out the foamed nickel after 1 hour, and putting the foamed nickel at 60 ℃ for vacuum drying for 12 hours to obtain the MXene/NF composite material;

(c) A0.4M aqueous solution of 2-methylimidazole was quickly poured into a 50mM aqueous solution of cobalt nitrate hexahydrate, and then a sheet of MXene/NF composite was immersed in the above mixed solution. After reacting for 4h, taking out a sample, washing the sample by using deionized water, and drying the sample at 60 ℃ overnight to obtain a Co-MOF @ MXene/NF composite material;

(d) and finally preparing a nano matrix CoP: a piece of Co-MOF @ MXene/NF composite material and NaH₂PO₂The powder (mass is 20 times of that of the Co-MOF @ MXene/NF composite material) is placed in two different positions of a ceramic boat, NaH₂PO₂Located on the upstream side of the tube furnace. Heating to 350 ℃ at the heating rate of 2 ℃/min under the nitrogen atmosphere, and keeping the temperature for 2h, wherein the nitrogen flow rate is 300 sccm. And obtaining the target product CoP @ MXene/NF composite material after the reaction is finished.

The CoP @ MXene/NF composite material is directly used as a working electrode in electrocatalytic integral water decomposition reaction, and the method comprises the following specific steps:

(1) the CoP @ MXene/NF composite material is directly used as a working electrode in electrocatalytic integral water decomposition reaction;

(2) preparing 1.0M potassium hydroxide solution as an electrocatalytic electrolyte, introducing nitrogen to drive air away, respectively taking a CoP @ MXene/NF composite material, an Ag/AgCl electrode and a platinum wire electrode as a working electrode, a reference electrode and a counter electrode to be connected with an electrochemical workstation, and measuring the electrocatalytic performance of the electrode material in the electrolyte.

As shown in FIG. 1, when the current density was 10mA/cm²When the hydrogen evolution overpotential of the CoP @ MXene/NF composite material is 260 mV; as shown in FIG. 2, when the current density was 10mA/cm²When the oxygen evolution overpotential of the CoP @ MXene/NF composite material is 320 mV. Compared with the Zn-doped CoP @ MXene/NF composite material, the HER performance and the OER performance of the CoP @ MXene/NF composite material are obviously poor, and the HER performance and the OER performance of the CoP @ MXene/NF composite material are due to the fact that the CoP @ MXene/NF composite material is not doped with Zn, so that the conductivity of the material is greatly reduced, and the electrocatalytic performance of the material is further reduced.

Comparative example 2:

compared with the embodiment 1, the method is mostly the same, except that the addition of sodium hypophosphite is omitted, i.e. no phosphorization is carried out, which greatly reduces the electrochemical performance of the material.

Preparation of ZnCo-LDH @ MXene/NF composite material

Raw materials:

hydrochloric acid (9M, 20mL)

Lithium fluoride (1.6g)

Titanium carbide aluminium (1g)

2-Methylimidazole aqueous solution (0.4M, 40mL)

Aqueous cobalt nitrate hexahydrate (50mM, 40mL)

Zinc nitrate hexahydrate (0.5mmol)

A ZnCo-LDH @ MXene/NF composite material is prepared by the following steps:

(a) 20mL (9M) of hydrochloric acid, 1.6g of lithium fluoride, was added to a polypropylene rubber bottle and magnetically stirred for 5 minutes. Then 1g of titanium aluminum carbide was slowly added and etching was carried out for 24 hours under 35 ℃ oil bath conditions. After etching was complete, 140ml of deionized water was added to the PVP vial, and the vial was then gently shaken and transferred to 4 centrifuge tubes. Centrifuging at 3000r/min for 5min, discarding the supernatant of the first two centrifugations, performing the third, fourth and fifth centrifugations, and collecting the supernatant after the third, fourth and fifth centrifugations to obtain monolayer or multilayer Xene aqueous suspension. N2 was then blown into the collected aqueous MXene suspension for 30min, then centrifuged at 10000r/min for half an hour, the precipitate was collected and freeze dried. When in use, the gel is dispersed in water to form MXene colloidal solution (4 mg/mL);

(c) A0.4M aqueous solution of 2-methylimidazole was quickly poured into a 50mM aqueous solution of cobalt nitrate hexahydrate, and then a sheet of MXene/NF composite was immersed in the above mixed solution. After reacting for 4h, taking out a sample, washing with deionized water, and drying at 60 ℃ overnight to obtain a Co-MOF @ MXene/NF composite material;

(d) then ZnCo-LDH arrays were prepared on Co-MOF @ MXene/NF composites: a piece of the Co-MOF @ MXene/NF composite was immersed in an aqueous ethanol solution (1: 4 volume ratio of ethanol to water, 100mL) containing zinc nitrate hexahydrate (0.5 mmol). After reacting for 15 minutes at 85 ℃, the purple color of the Co-MOF disappears, then taking out a sample, repeatedly washing the sample by using ethanol and water, and drying the sample at 60 ℃ to obtain the ZnCo-LDH @ MXene/NF composite material.

The ZnCo-LDH @ MXene/NF composite material is directly used as a working electrode in electrocatalytic integral water decomposition reaction, and the method comprises the following specific steps:

(1) the ZnCo-LDH @ MXene/NF composite material is directly used as a working electrode in electrocatalytic integral water decomposition reaction;

(2) preparing 1.0M potassium hydroxide solution as an electrocatalysis electrolyte, introducing nitrogen to drive air away, taking the ZnCo-LDH @ MXene/NF composite material, the Ag/AgCl electrode and the platinum wire electrode as a working electrode, a reference electrode and a counter electrode respectively, connecting an electrochemical workstation, and measuring the electrocatalysis performance of the electrode material in the electrolyte.

As shown in FIG. 1, when the current density was 10mA/cm²When the hydrogen evolution overpotential of the ZnCo-LDH @ MXene/NF composite material is 320 mV; as shown in FIG. 2, when the current density was 10mA/cm²When the composite material is used, the oxygen evolution overpotential of the ZnCo-LDH @ MXene/NF composite material is 390 mV. Compared with the Zn-coped CoP @ MXene/NF composite material, the HER performance and the OER performance of the ZnCo-LDH @ MXene/NF composite material are obviously deteriorated due to the fact that the ZnCo-LDH @ MXene/NF composite material is not phosphorized and does not contain CoP nanosheets grown in an array, so that the conductivity of the material is greatly reduced, and the electrocatalytic performance of the material is further reduced.

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims

1. A synthetic method of a Zn-coped CoP @ MXene/NF composite material is characterized by comprising the following steps:

2. The synthesis method of the Zn-coped CoP @ MXene/NF composite material according to claim 1, wherein in the step (1), the inorganic salt is lithium fluoride, and the strong acid is hydrochloric acid;

the concentration of the hydrochloric acid is 9M, and the adding amount ratio of the lithium fluoride, the hydrochloric acid and the titanium aluminum carbide is 1.6g:20mL:1 g.

3. The synthesis method of the Zn-doped CoP @ MXene/NF composite material according to claim 1, wherein in the step (1), the etching temperature is 20-40 ℃ and the etching time is 20-30 h.

4. The synthesis method of the Zn-doped CoP @ MXene/NF composite material according to claim 1, wherein in the step (2), the concentration of the MXene colloidal solution is 1-4 mg/mL;

the soaking time of the foamed nickel in the MXene colloidal solution is 1-3 h.

5. The method for synthesizing Zn-coped CoP @ MXene/NF composite material according to claim 4, wherein in the step (3), the accelerator is 0.4M 2-methylimidazole aqueous solution, the cobalt source is 50mM cobalt nitrate hexahydrate aqueous solution, the size of the MXene/NF composite material is 1cm by 2cm by 2.5mM, and the amount of the added 2-methylimidazole aqueous solution and the amount of the added cobalt nitrate hexahydrate aqueous solution are 40mL and 40mL respectively;

in the step (3), the reaction time is 3-5 h.

6. The method for synthesizing the Zn-coped CoP @ MXene/NF composite material according to claim 5, wherein in the step (4), the zinc source is zinc nitrate hexahydrate, and the volume ratio of ethanol to water in the ethanol aqueous solution is 1: 4, the size of the Co-MOF @ MXene/NF composite material is 1cm by 2cm by 2.5mm, and the amount of zinc nitrate hexahydrate and the amount of ethanol water solution added correspondingly are 0.5mmol and 100mL respectively;

in the step (4), the reaction temperature is 60-90 ℃, and the reaction time is 10-20 min.

7. The method for synthesizing Zn-coped CoP @ MXene/NF composite material according to claim 1, wherein in the step (5), in the separated gas phosphating reaction, the phosphating agent is NaH₂PO₂Powder;

in the step (5), the ZnCo-LDH @ MXene/NF composite material and NaH are adopted₂PO₂The mass ratio of the powders is1：20。

8. The synthesis method of the Zn-coped CoP @ MXene/NF composite material according to claim 1, wherein in the step (5), in the separated gas phosphating reaction, the annealing temperature is 100-350 ℃, the heat preservation time is 2h, and the heating rate is 1-3 ℃/min.

9. A Zn-coped CoP @ MXene/NF composite material, characterized in that it is prepared by the synthesis method according to any of claims 1 to 8.

10. The use of a Zn-doped CoP @ MXene/NF composite as claimed in claim 9, wherein the composite is used in electrocatalytic bulk water splitting reaction.