CN113594476B - A kind of carbon nitride modified methanol electrocatalyst and preparation method and application thereof - Google Patents

Abstract

The present invention provides a carbon nitride-modified methanol electrocatalyst and its preparation method and application. The present invention uses carbon materials and nitrogen-containing compounds as precursors, and obtains carbon nitride/carbon materials after uniform mixing and high-temperature calcination. And take this as the matrix, add nickel salt, manganese salt and urea to the mixed solution of water and alcohol, and then the carbon nitride modified NiMn double metal hydroxide/carbon nanocomposite can be prepared after hydrothermal reaction. , the material is rich in oxygen vacancies and exhibits excellent electrocatalytic activity for methanol. Instead of traditional noble metal catalysts, a cheap and easily available electrocatalyst with outstanding electrocatalytic activity is provided for methanol fuel cells.

Description

A kind of carbon nitride modified methanol electrocatalyst and preparation method and application thereof

technical field

The invention relates to the preparation of carbon nitride-based nanomaterials and the application field thereof, in particular to a carbon nitride-modified methanol electrocatalyst and a preparation method and application thereof, in particular to a carbon nitride-modified NiMn bimetallic oxidation catalyst Preparation of nanomaterials and their application in methanol fuel cells.

Background technique

With the increasing energy crisis and environmental pollution, people need to urgently develop a new type of clean and sustainable energy. Methanol fuel cells have received extensive attention due to their high energy density and low environmental pollution. At present, the key to the preparation of methanol fuel cells is to design and construct electrocatalysts with high electrocatalytic activity and cheap and easy to obtain, so as to replace the traditional precious metal catalysts.

Double metal hydroxides are currently considered as one of the most competitive candidates for methanol oxidation electrocatalysts. Among them, NiMn double metal hydroxide (NiMn LDH) also showed certain electrocatalytic activity. However, due to the poor conductivity and slow mass transfer rate of NiMn LDH, its activity cannot meet commercial demands.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a carbon nitride-modified methanol electrocatalyst and a preparation method thereof, which are NiMn bimetallic oxide nanomaterials modified by carbon nitride rich in oxygen vacancies. The material is used as a carrier, carbon nitride material is first prepared, and then NiMn double metal hydroxide is deposited on the carbon nitride material through a hydrothermal reaction to prepare a carbon nitride modified methanol electrocatalyst. In the catalyst, the NiMn double metal hydroxide generates oxygen vacancies due to the strong adsorption effect of carbon nitride on hydroxyl groups, and the content of the oxygen vacancies reaches 40%; the preparation method is simple and the product morphology is uniform.

Another object of the present invention is to provide the application of a carbon nitride modified methanol electrocatalyst in methanol fuel cells.

The specific technical scheme of the present invention is as follows:

A preparation method of a carbon nitride-modified methanol electrocatalyst, comprising the following steps:

A. Disperse the carbon material and the nitrogen-containing compound in water and stir evenly. After freeze-drying, the resulting mixture is calcined, which is carbon nitride/carbon material;

B. Disperse the carbon nitride/carbon material in a mixed solvent to form a uniformly dispersed dispersion;

C, under the state of stirring, the nickel-manganese mixed solution is added dropwise to the dispersion liquid prepared by step B, then urea is added, and hydrothermal reaction obtains the NiMn double metal hydroxide/carbon modified by carbon nitride. Nanocomposites.

In step A, described water is deionized water;

In step A, the freeze-drying conditions are: drying at -40°C～-80°C and vacuum degree of 0.1-30Pa for 12-48h;

In step A, freeze-drying enables the carbon material and the nitrogen-containing chemical to be fully mixed and uniform, so that the nitrogen-containing compound does not volatilize;

In step A, the carbon material includes one or more of carbon black, graphene or carbon nanotubes; the nitrogen-containing chemical is one or more of urea, dicyandiamide or melamine;

The mass ratio of the carbon material and the nitrogen-containing compound in step A is between 2:1-1:3;

The consumption ratio of carbon material and water described in step A is 0.2-5mg/ml;

The calcination temperature range in step A is between 400°C and 700°C, and the calcination is performed for 0.5h-2h.

The mixed solvent described in step B refers to the mixed solvent of water and alcohol;

The mixed solvent of water and alcohol in step B helps to disperse the carbon nitride/carbon composite;

In step B, by ultrasonic for 0.5-2h, a uniformly dispersed dispersion liquid is formed;

In the mixed solvent of water and alcohol described in step B, the volume ratio of alcohol to water is 1:0.1-1:10;

In step B, the alcohol is selected from any one or a combination of ethylene glycol, ethanol and methanol.

The carbon nitride/carbon material and mixed solvent dosage ratio described in step B is 0.2-2mg/ml;

The nickel-manganese mixed solution preparation method described in step C is: dissolving nickel salt and manganese salt in a mixed solvent of water and alcohol; the nickel salt is selected from nickel chloride hexahydrate, nickel nitrate hexahydrate, nickel sulfate hexahydrate or Nickel acetate tetrahydrate; the manganese salt is a soluble manganese salt, selected from manganese nitrate, manganese sulfate monohydrate, manganese acetate tetrahydrate or manganese chloride tetrahydrate; the total mass of the nickel salt and manganese salt and the consumption of the mixed solvent The ratio is between 1-10 mg/mL; the molar ratio of the nickel salt and the manganese salt is 2:1-25:1;

The volume ratio of the nickel-manganese mixed solution in step C and the dispersion liquid in step B is between 0.1:1-10:1;

The mixed solvent of water and alcohol described in step C is identical with the mixed solvent described in step B;

The effect of urea in step C is to provide weak alkaline environment;

In step C, dropwise addition enables the metal salt to be uniformly dissolved in the dispersion prepared in step B;

In step C, the consumption of urea and the total mass ratio of nickel salt and manganese salt are between 1:1-100:1;

The hydrothermal reaction in step C refers to: reacting at 70-180°C for 4-48 hours;

In step C, after the hydrothermal reaction is completed, the precipitation is cooled, separated, the precipitation is washed first with water, then with alcohol, and dried in vacuum at 40-60° C. to constant weight to obtain a carbon nitride-modified NiMn double metal hydroxide / carbon nanocomposite, i.e. carbon nitride modified methanol electrocatalyst;

In step C, the carbon nitride-modified NiMn double metal hydroxide/carbon nanocomposite is rich in oxygen vacancies;

In step C, the amount of carbon nitride is controlled by adjusting the concentration of the dispersion liquid in step B and the amount ratio of the metal salt in step C. Carbon nitride can absorb the hydroxide of NiMn double metal hydroxide through the principle of electronegativity to obtain different contents of oxygen. vacancy samples, and the content of oxygen vacancies is 5%-40%.

The carbon nitride-modified NiMn double metal hydroxide/carbon nanocomposite in step C has a sheet-like structure. The size is between 100nm-500nm.

A carbon nitride modified methanol electrocatalyst provided by the present invention is prepared by the above method, and the carbon nitride modified NiMn double metal hydroxide/carbon nanocomposite prepared above has a sheet-like structure, that is, nitrogen Carbon-modified methanol electrocatalysts.

The application of a carbon nitride modified methanol electrocatalyst provided by the invention is the application in methanol electrocatalysis.

The electrocatalytic performance test method is as follows:

1) ultrasonically disperse the carbon nitride-modified methanol electrocatalyst in deionized water to form a dispersion solution;

2) Prepare 0.1M KOH with deionized water and contain 0.1M methanol solution; then, absorb the dispersion solution of carbon nitride-modified methanol electrocatalyst, drop it on the surface of the glassy carbon electrode, and place it to dry naturally;

3) The electrocatalytic process of methanol was recorded in the potential window of 0.0～0.8V vs. Ag/AgCl using an electrochemical workstation.

Carbon nitride (C ₃ N ₄ ) has certain research potential in the field of catalysis due to its good chemical stability and unique electronic structure. C ₃ N ₄ can improve the conductivity of the target material through the coupling effect between the bimetals, generate a large number of oxygen vacancies, and improve the catalytic activity of the material. _The present invention uses the _NiMn LDH/carbon nanocomposite material modified with C3N4 and containing oxygen vacancies as the methanol oxidation electrocatalyst.

In the present invention, carbon material and nitrogen-containing compound are used as precursors, and carbon nitride/carbon material is prepared after uniform mixing and high-temperature calcination, and this is used as a matrix, and nickel salt, manganese salt and urea are added to the mixed solution of water and alcohol. , and after hydrothermal reaction, carbon nitride-modified NiMn bimetallic hydroxide/carbon nanocomposites can be prepared, which are rich in oxygen vacancies and exhibit excellent electrocatalytic activity for methanol.

Compared with the prior art, the method of the carbon nitride modified NiMn double metal hydroxide/carbon nanocomposite prepared by the present invention is simple, the appearance is uniform, and due to the strong adsorption effect of carbon nitride on hydroxyl, the NiMn double metal hydroxide composites generate a large number of oxygen vacancies with content up to 40%. Moreover, the carbon nitride-modified NiMn double metal hydroxide/carbon nanocomposites prepared in this method have excellent electrocatalytic activity towards methanol, and the activity for 0.1 M methanol in 0.1 M KOH solution is as high as 64 mA·cm ^-2 . In addition, the electrocatalytic activity of this catalyst relative to NiMn bimetallic hydroxide/carbon nanocomposites is enhanced by 5-32 times due to the effect of oxygen vacancies.

The invention uses transition metal compounds as raw materials, and carbon nitride is modified to replace traditional precious metal catalysts, thereby providing a cheap and easily available electrocatalyst with outstanding electrocatalytic activity for methanol fuel cells. Moreover, the nanocomposite catalyst also has the advantages of simple preparation method and uniform morphology. Its application in the field of methanol electrocatalysis can provide a feasible idea for solving the current increasingly serious energy crisis and environmental pollution problems.

Description of drawings

Fig. 1 is the X-ray powder diffraction XRD pattern of the carbon nitride modified NiMn double metal hydroxide/graphene nanomaterial prepared in Example 1;

Fig. 2 is the transmission electron microscope SEM photograph of the carbon nitride modified NiMn double metal hydroxide/graphene nanomaterial of embodiment 1 gained;

Fig. 3 is the XPS figure of the carbon nitride modified NiMn double metal hydroxide/graphene nanomaterial of embodiment 1 gained;

Fig. 4 is the surface element analysis diagram of the carbon nitride modified NiMn double metal hydroxide/carbon graphene nanomaterial of embodiment 1 gained;

Fig. 5 is the electron paramagnetic resonance spectrum of NiMn double metal hydroxide/graphene nanomaterials and NiMn double metal hydroxide/graphene nanomaterials modified by carbon nitride obtained in Example 1;

Fig. 6 is the oxygen high-resolution XPS image of the carbon nitride-modified NiMn double metal hydroxide/graphene nanomaterial obtained in Example 1;

Fig. 7 is the methanol oxidation CV diagram of the carbon nitride modified NiMn double metal hydroxide/graphene nanomaterial obtained in Example 1;

8 is a CV diagram of methanol oxidation of the NiMn double metal hydroxide/graphene nanomaterial obtained in Example 1.

Detailed ways

The present invention will be described in detail below in conjunction with the examples.

Example 1

A preparation method of a carbon nitride-modified methanol electrocatalyst, comprising the following steps:

A. Mixing: At room temperature, 100 mg of urea and 100 mg of graphene were added to 50 mL of deionized water and ultrasonically dispersed to uniformly disperse them. Dry at -40 °C and a vacuum of 0.5 Pa for 40 h; freeze-drying in an air atmosphere Internally calcined at 550°C for 2h; after cooling, the carbon nitride/graphene composite material is obtained;

B. Dispersion: Weigh 8 mg of carbon nitride/graphene composite material in 10 mL of a mixed solvent of ethylene glycol and water with a volume ratio of 1:1, and ultrasonically disperse it uniformly for 0.5 h;

C. Preparation: 0.0470g of nickel chloride hexahydrate and 0.0025g of manganese chloride tetrahydrate were added to a mixed solution of 10 mL of ethylene glycol and water (specific volume 1:1) at room temperature, and then the solution was added under stirring Slowly add dropwise to the dispersion of step B, then add 150 mg of urea, and finally, heat the obtained solution to 120 ° C, and the reaction time is 10 hours;

D. Drying: Cool and separate the reacted system, wash the precipitate first with water, then with alcohol, and vacuum dry at 60°C to constant weight, that is, carbon nitride-modified NiMn double metal hydroxide/graphene composite material (NiMn LDH/C ₃ N ₄ /G), EPR test shows that the NiMn LDH/C ₃ N ₄ /G composite contains a large number of oxygen vacancies (Fig. 5), and the content of oxygen vacancies reaches 40% (Fig. 6), namely Carbon nitride-modified methanol electrocatalysts.

Electrocatalytic performance test:

The NiMn LDH/C ₃ N ₄ /G obtained in Example 1 was used as a catalyst for the electrocatalytic reaction of methanol:

First, weigh a certain amount of NiMn LDH/C ₃ N ₄ /G nanomaterials, and ultrasonically disperse them in deionized water to prepare a 4 mg/L dispersion solution; secondly, use deionized water to prepare 0.1M KOH containing 0.1 M methanol solution; then, 6 μL of 4 mg/L dispersion solution was dropped on the surface of the glassy carbon electrode and dried naturally; finally, in 0.1 M KOH solution, the potential window was 0.0-0.8 V vs. Ag/AgCl using an electrochemical workstation The electrocatalytic process for methanol was recorded. It can be seen that under the condition of 0.0M methanol, the _NiMnLDH /C ₃ N ₄ /G nanocomposite has only a weak background current _. Good electrocatalytic reaction, and its catalytic current can reach 64 mA·cm ^-2 (Fig. 7).

Meanwhile, NiMn LDH/G nanocomposites were prepared as a comparison, and the preparation procedure was as follows

A. Dispersion: Weigh 8 mg of graphene in 10 mL of a mixed solvent of ethylene glycol and water with a volume ratio of 1:1, and ultrasonically disperse it uniformly;

B. Preparation: 0.0470g of nickel chloride hexahydrate and 0.0025g of manganese chloride tetrahydrate were added to a mixed solution of 10 mL of ethylene glycol and water (specific volume 1:1) at room temperature, and then the solution was slowly stirred under the action of Add dropwise to the dispersion of step B and add 150 mg of urea, and finally, the obtained solution is heated to 120 ° C, and the reaction time is 10 hours;

C. Drying: Cool and separate the reacted system, wash the precipitate first with water, then with alcohol, and vacuum dry at 60°C to constant weight, namely NiMn double metal hydroxide/graphene composite material (NiMn LDH/G) , EPR indicated that the oxygen vacancy content of this material is almost negligible (Fig. 5). In 0.1M KOH solution, NiMn LDH/G has a weak response current at 0.0M methanol concentration, and the catalytic current for 0.1M methanol is only 2 mA·cm ^-2 (Fig. 8). In comparison, the electrocatalytic current of NiMn LDH/C ₃ N ₄ /G nanocomposite is increased by 32 times.

Example 2

A preparation method of a carbon nitride-modified methanol electrocatalyst, comprising the following steps:

A. Mixing: At room temperature, 50mg of melamine and 50mg of carbon black were added to 30mL of deionized water and ultrasonically dispersed to make it evenly dispersed, dried at -50°C and vacuum of 10Pa for 20h, freeze-dried in an air atmosphere Calcined at 550℃ for 2h; after cooling, it is carbon nitride/carbon black composite material

B. Dispersion: Weigh 6 mg of carbon nitride/carbon black composite material in 10 mL of a mixed solvent of ethanol and water with a volume ratio of 1:1, and ultrasonicate for 1 h to make it uniformly dispersed;

C. Preparation: 0.0580g nickel nitrate hexahydrate and 0.0025g manganese nitrate are added to a mixed solution of 10mL ethanol and water (specific volume 1:1) at room temperature, and then this solution is slowly added dropwise to step B under stirring 300mg of urea was added to the dispersion liquid, and finally, the obtained solution was heated to 100°C, and the reaction time was 18 hours;

D. Drying: Cool and separate the reacted system, wash the precipitate first with water, then with alcohol, and vacuum dry at 40°C to constant weight, that is, carbon nitride modified NiMn bimetallic hydroxide containing oxygen vacancies/ Carbon black nanocomposite (NiMn LDH/C ₃ N ₄ /C) with an oxygen vacancy content of 22%.

Electrocatalytic performance test:

The NiMn LDH/C ₃ N ₄ /C obtained in Example 2 was used as a catalyst for the electrocatalytic reaction of methanol:

First, a certain amount of NiMn LDH/C ₃ N ₄ /C nanomaterials were weighed and ultrasonically dispersed in deionized water to prepare a 3 mg/L dispersion solution; secondly, 0.1 M KOH was prepared with deionized water and contained 0.1 M methanol solution; then, 6 μL of 5 mg/L dispersion solution was dropped on the surface of the glassy carbon electrode and cooled naturally; finally, the electrochemical workstation was used to record its effect on methanol between the potential window of 0.0-0.8 V vs. Ag/AgCl From the electrocatalytic process, it can be seen that the obtained NiMn LDH/C ₃ N ₄ /C nanocomposite has a good electrocatalytic reaction to methanol. The NiMn LDH/C ₃ N ₄ /C nanocomposite has a catalytic activity of 48 mA·cm ^-2 for methanol at 0.1 M in 0.1 M KOH solution.

Under the same conditions, NiMn double metal hydroxide/carbon black nanocomposites (NiMn LDH/C) were prepared for comparison, and the preparation procedure was as follows

A. Dispersion: Weigh 6 mg of carbon black into 10 mL of a mixed solvent of ethanol and water with a volume ratio of 1:1, and ultrasonically disperse it uniformly;

B. Preparation: 0.0580g nickel nitrate hexahydrate and 0.0025g manganese nitrate hexahydrate were added to a mixed solution of 10mL ethanol and water (specific volume 1:1) at room temperature, and then the solution was slowly added dropwise under stirring Add 300 mg of urea to the dispersion of step B, and finally, heat the obtained solution to 100 ° C, and the reaction time is 18 hours;

C. Drying: the reacted system is cooled and separated, the precipitate is washed with water first, then washed with alcohol, and dried under vacuum at 40°C to constant weight, that is, NiMn double metal hydroxide/carbon black nanocomposite (NiMn LDH/C ).

In 0.1M KOH solution, the catalytic activity of NiMn LDH/C composite towards 0.1M methanol is only 2 mA·cm ^-2 . In comparison, the electrocatalytic activity of NiMn LDH/C ₃ N ₄ /C nanocomposites is enhanced by 24 times.

Example 3

A preparation method of a carbon nitride-modified methanol electrocatalyst, comprising the following steps:

A. Mixing: At room temperature, 100 mg of dicyandiamide and 100 mg of carbon nanotubes were added to 60 mL of deionized water and ultrasonically dispersed to make them evenly dispersed, dried at -80 °C and a vacuum of 20 Pa for 15 h, and dried in air. Calcined at 600℃ for 2h in the atmosphere; after cooling, it is carbon nitride/carbon nanotube composites

B. Dispersion: Weigh 8 mg of carbon nitride/carbon nanotube composite material in 10 mL of a mixed solvent of methanol and water with a volume ratio of 1:1, and sonicate for 1 h;

C, preparation: at room temperature, add 0.0650g nickel sulfate hexahydrate and 0.0035g manganese sulfate monohydrate to a mixed solution of 10mL ethylene glycol and water (specific volume 1:1), then slowly drop this solution under the action of stirring To the dispersion of step B, add 180 mg of urea, and finally, the obtained solution is heated to 80 ° C, and the reaction time is 24 hours;

D. Drying: Cool and separate the reacted system, wash the precipitate first with water, then with alcohol, and vacuum dry at 60°C to constant weight, that is, carbon nitride modified NiMn bimetallic hydroxide containing oxygen vacancies/ Carbon nanotube nanocomposite (NiMnLDH/C ₃ N ₄ /CNT), and the content of oxygen vacancies is 29%.

Electrocatalytic performance test:

The NiMn LDH/C ₃ N ₄ /CNT obtained in Example 3 was used as a catalyst for the electrocatalytic reaction of methanol:

First, a certain amount of NiMn LDH/C ₃ N ₄ /CNT nanomaterials were weighed and ultrasonically dispersed in deionized water to prepare a 4 mg/L dispersion solution; secondly, 0.1 M KOH was prepared with deionized water and contained 0.1 M methanol solution; then, 6 μL of 4 mg/L dispersion solution was dropped on the surface of the glassy carbon electrode and cooled naturally; finally, the electrochemical workstation was used to record its effect on methanol with a potential window of 0.0-0.8 V vs. Ag/AgCl. The electrocatalytic process, it can be seen that the obtained NiMn LDH/C ₃ N ₄ /CNT nanocomposite has a good electrocatalytic reaction to methanol. In 0.1M KOH solution, the NiMn LDH/C ₃ N ₄ /CNT nanocomposite has a catalytic activity of 52 mA·cm ^-2 for methanol at 0.1 M.

Under the same conditions, NiMn double metal hydroxide/carbon nanotube nanocomposites (NiMn LDH/C ₃ N ₄ /CNT) were prepared as a comparison, and the preparation procedure was as follows:

A. Dispersion: Weigh 8 mg of carbon nanotube composite material in 10 mL of a mixed solvent of methanol and water with a volume ratio of 1:1, and ultrasonically disperse it uniformly;

B, preparation: at room temperature, add 0.0650g nickel sulfate hexahydrate and 0.0035g manganese sulfate monohydrate to a mixed solution of 10mL ethylene glycol and water (specific volume 1:1), then slowly drop this solution under the action of stirring In the dispersion liquid of step B, add 180mg urea again, and finally, the obtained solution is heated to 80 ℃, and the reaction time is 24 hours;

C. Drying: the reacted system is cooled and separated, the precipitate is washed with water first, then washed with alcohol, and dried under vacuum at 60°C to constant weight, that is, NiMn double metal hydroxide/carbon nanotube nanocomposite material (NiMn LDH /C ₃ N ₄ /CNT). In 0.1M KOH solution, the catalytic activity of NiMn LDH/C ₃ N ₄ /CNT towards methanol at 0.1 M is only ₃ mA·cm ^-2 _. The catalytic activity was increased by 17 times.

Example 4

A preparation method of a carbon nitride-modified methanol electrocatalyst, comprising the following steps:

A. Mixing: At room temperature, 70 mg of urea and 100 mg of graphene were added to 40 mL of deionized water, and ultrasonically dispersed to uniformly disperse them. Dry for 40 hours at -55 °C and a vacuum of 15 Pa; freeze-dried in an air atmosphere. Calcined at 550℃ for 2h; after cooling, it is carbon nitride/graphene composite material

B. Dispersion: Weigh 5 mg of carbon nitride/graphene composite material in 10 mL of a mixed solvent of ethylene glycol and water with a volume ratio of 1:1, and ultrasonically disperse it uniformly;

C. Preparation: 0.0540g of nickel chloride hexahydrate and 0.0060g of manganese acetate tetrahydrate were added to a mixed solution of 10 mL of ethylene glycol and water (specific volume 1:1) at room temperature, and then the solution was slowly dripped under the action of stirring Add to the dispersion of step B, then add 130 mg of urea, and finally, the obtained solution is heated to 120 ° C, and the reaction time is 10 hours;

D. Drying: Cool and separate the reacted system, wash the precipitate first with water, then with alcohol, and vacuum dry at 60°C to constant weight, that is, carbon nitride modified NiMn bimetallic hydroxide containing oxygen vacancies/ Graphene nanocomposite (NiMn LDH/C ₃ N ₄ /G) with an oxygen vacancy content of 12%.

Electrocatalytic performance test:

The NiMn LDH/C ₃ N ₄ /G obtained in Example 4 was used as a catalyst for the electrocatalytic reaction of methanol:

First, weigh a certain amount of NiMn LDH/C ₃ N ₄ /G nanomaterials, and ultrasonically disperse them in deionized water to prepare a 4 mg/L dispersion solution; secondly, use deionized water to prepare 0.1M KOH containing 0.1 M methanol solution; then, 6 μL of 4 mg/L dispersion solution was dropped on the surface of the glassy carbon electrode and cooled naturally; finally, the electrochemical workstation was used to record its effect on methanol with a potential window of 0.0-0.8 V vs. Ag/AgCl. From the electrocatalytic process, it can be seen that the obtained NiMn LDH/C ₃ N ₄ /G nanocomposite has a good electrocatalytic reaction to methanol. The NiMn LDH/C ₃ N ₄ /G nanocomposite has a catalytic activity of 38 mA·cm ^-2 for methanol at 0.1 M in 0.1 M KOH solution.

The NiMn double metal hydroxide/graphene nanocomposite (NiMn LDH/C ₃ N ₄ /G) was prepared under the same conditions for comparison. The preparation procedure is as follows:

A. Dispersion: Weigh 5 mg of graphene in 10 mL of a mixed solvent of ethylene glycol and water with a volume ratio of 1:1, and ultrasonically disperse it uniformly;

B, preparation: at room temperature, add 0.0540g nickel chloride hexahydrate and 0.0060g manganese acetate tetrahydrate to a mixed solution of 10mL ethylene glycol and water (specific volume 1:1), then slowly drop this solution under the action of stirring Add to the dispersion of step B and add 130 mg of urea, and finally, the obtained solution is heated to 120 ° C, and the reaction time is 10 hours;

C. Drying: Cool and separate the reacted system, wash the precipitate first with water, then with alcohol, and vacuum dry at 60°C to constant weight, namely NiMn double metal hydroxide/graphene nanocomposite (NiMn LDH/C _3N4 /G ₎ .

In 0.1M KOH solution, the catalytic activity of NiMn LDH/G nanocomposites for methanol at 0.1 M is only 3 mA·cm ^-2 , while under the same conditions, the electrocatalytic activity of NiMn LDH/C ₃ N ₄ /G nanocomposites Activity increased 13 times.

Claims (6)

1. a preparation method of a carbon nitride modified methanol electrocatalyst, the preparation method comprises the following steps: A. Disperse the carbon material and the nitrogen-containing compound in water and stir evenly. After freeze-drying, the resulting mixture is calcined, which is carbon nitride/carbon material; B. Disperse the carbon nitride/carbon material in a mixed solvent to form a uniformly dispersed dispersion; C, under the state of stirring, the nickel-manganese mixed solution is added dropwise to the dispersion liquid prepared by step B, then urea is added, and hydrothermal reaction is obtained to obtain the NiMn double metal hydroxide/carbon modified by carbon nitride. nanocomposites; The calcination temperature range in step A is 400°C-700°C, and the calcination time is 0.5-2h; Carbon nitride/carbon material and mixed solvent dosage ratio described in step B are 0.2-2mg/ml; The method for preparing the nickel-manganese mixed solution in step C is as follows: dissolving nickel salt and manganese salt in a mixed solvent of water and alcohol; the ratio of the total mass of the nickel salt and manganese salt to the mixed solvent is 1-10 mg/ Between mL; the molar ratio of the nickel salt and the manganese salt is 2:1-25:1; The volume ratio of the nickel-manganese mixed solution of step C and the dispersion liquid of step B is between 0.1:1-10:1; The hydrothermal reaction in step C refers to: reacting at 70-180°C for 4-48 hours; The content of oxygen vacancies in the prepared carbon nitride-modified methanol electrocatalysts ranges from 5 % to 40 %. 2. The preparation method according to claim 1, wherein the carbon material in step A comprises one or more of carbon black, graphene or carbon nanotubes; the nitrogen-containing compound is urea, dicyano One or more of amine or melamine. 3. The preparation method according to claim 1 or 2, wherein the mass ratio of the carbon material and the nitrogen-containing compound in step A is between 2:1 and 1:3. 4. preparation method according to claim 1 is characterized in that, the mixed solvent described in step B refers to the mixed solvent of water and alcohol. 5. preparation method according to claim 1 and 2 is characterized in that, in step C, the consumption of urea and nickel salt and manganese salt total mass ratio are between 1:1-100:1. 6. Application of a carbon nitride-modified methanol electrocatalyst prepared by the preparation method according to any one of claims 1-5 in methanol electrocatalysis.

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