Ultra-thin carbon-layer composite material modified by nickel nanoclusters and vanadium carbide particles and its preparation method and application

Abstract

The invention relates to an ultra-thin carbon-layer composite material modified by nickel nanoclusters and vanadium carbide particles, and its preparation method and application. The composite material comprises a two-dimensional ultra-thin carbon-layer as a matrix, in which nickel clusters and vanadium carbide nanoparticles are embedded to form coupling interfaces between Ni and C, VC and C, and Ni and VC. The thickness of the two-dimensional ultra-thin carbon-layer is less than 10 nm.

Claims

1. A preparation method of a carbon-layer composite material modified by nickel nanoclusters and vanadium carbide particles, comprising: (1) mixing a carbon source and a precursor at a mass ratio of (2 to 4):1 to obtain a raw material mixture; and (2) putting the raw material mixture in an inert atmosphere, heating at 500 to 550° C. for 1 to 2.5 hours, and then heating at 800 to 900° C. for 1.5 to 2.5 hours, to obtain the composite material, wherein the precursor is obtained via microwave hydrothermal reaction of an aqueous solution followed by an ultrasonic treatment, wherein the aqueous solution comprises a nickel source, a vanadium source, and an alkali source, and wherein a mole ratio of the nickel source, the vanadium source, and the alkali source is (0.5 to 2):1:(1.5 to 1.6).

2. The preparation method of claim 1, wherein the nickel source is selected from at least one of nickel nitrate hexahydrate, nickel sulfate hexahydrate, and nickel chloride hexahydrate, and wherein the vanadium source is vanadium chloride, and the alkali source is urea.

3. The preparation method of claim 1, wherein the heating process comprises: heating from room temperature at a heating rate of 3 to 5° C./min to 500 to 550° C. which is maintained for 1.5 to 2 hours; heating to 800 to 900° C. at a heating rate of 3 to 5° C./min and calcining for 1.5 to 2.5 hours; and cooling to 300° C. at a cooling rate of 8 to 10° C./min, and then to room temperature via natural cooling.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an X-ray spectrum of the Ni/VC@C composite material prepared in example 2;

(2) FIG. 2 is an XPS spectrum of the nitrogen in the composite material prepared in example 1;

(3) FIG. 3 is a transmission electron microscope image of the Ni/VC@C composite material prepared in example 1;

(4) FIG. 4 is a transmission electron microscope image of the Ni/VC@C composite material prepared in example 2;

(5) FIG. 5 is a transmission electron microscope image of the Ni/VC@C composite material prepared in example 4;

(6) FIG. 6 is a HER performance graph of the Ni/VC@C composite material prepared in example 2 under alkaline conditions;

(7) FIG. 7 is a HER performance graph of the Ni/VC@C composite material prepared in example 3 under acidic conditions;

(8) FIG. 8 is a HER performance graph of the Ni/VC@C composite material prepared in example 1 under neutral conditions.

DETAILED DESCRIPTION

(9) Hereinafter, the present invention will be further described with the following examples. It should be understood that the following examples are used to explain this invention and do not mean to limit the scope of this invention.

(10) In the present invention, an ultra-thin carbon-layer composite material modified by nickel nanoclusters and vanadium carbide particles comprises a two-dimensional ultra-thin carbon which has been partially graphitized, and metallic nickel clusters and vanadium carbide particles with controllable particle sizes embedded in the ultra-thin carbon layer. In an optional embodiment, the vanadium carbide nanoparticles have a particle size of about 3 to 15 nm, a uniform morphology, a high crystallinity, and good dispersion. The particle size of the nickel clusters is about 3 to 15 nm. Metallic nickel clusters and vanadium carbide nanoparticles are distributed uniformly in the ultra-thin carbon layer, which work together to improve the electrocatalytic hydrogen evolution performance of the ultra-thin carbon layer.

(11) The following is an exemplarily description of the preparation method of an ultra-thin carbon-layer composite material modified by nickel nanoclusters and vanadium carbide particles provided by the present invention.

(12) Preparation of nickel vanadium double metal hydroxide: A nickel source, a vanadium source, and an alkali source are mixed with a solution, which then undergo a microwave hydrothermal reaction at 90 to 110° C., to obtain nickel vanadium double metal hydroxide. The nickel source is selected from nickel nitrate hexahydrate, nickel sulfate hexahydrate, or nickel chloride hexahydrate, etc. The vanadium source is vanadium chloride, etc. The alkali source is urea. The mole ratio of the nickel source, the vanadium source, and the alkali source is (0.5 to 2):1:(1.5 to 1.6). The microwave hydrothermal reaction continues for 2 to 4 hours at a power of 200 to 400 W.

(13) Preparation of a precursor A: The resulting nickel vanadium double metal hydroxide is treated with ultrasonic processing for 1 to 2 hours in an ethanol solution at a temperature of 60 to 80° C. and a power of 180 to 200 W, which is then dried at room temperature to produce pretreated double metal hydroxide, referred as the precursor A.

(14) An example of the preparation of nickel vanadium double metal hydroxide comprises the following steps: nickel chloride hexahydrate, vanadium chloride and urea are mixed at the specified mole ratio, and then are added to 20 to 25 ml ultra-pure water under stirring for 10 to 15 minutes, to obtain solution A. The mixed solution A is put into a microwave apparatus to react for 2 to 4 hours at a temperature of 90 to 110° C. and a power of 200 to 400 W, and the reaction mixture is then cooled down to room temperature. Finally, the product is cleaned with ultra-pure water and absolute ethanol for 2 to 3 times respectively, and then dried for 4 to 5 hours in a vacuum drying oven to give the nickel vanadium double metal hydroxide.

(15) The nickel vanadium double metal hydroxide is treated with ultrasonic processing for 1 to 2 hours in an ethanol solution at a temperature of 60 to 80° C. and a power of 180 to 200 W, which is dried at room temperature to finally give the precursor A.

(16) A carbon source and the precursor A are mixed and ground thoroughly to give a mixture of raw material. The carbon source is dicyandiamide and the ratio of the carbon source and the precursor A is (2 to 4):1. The grinding may continue 20 to 30 minutes.

(17) The mixture of raw material is put into a container (such as a crucible or a combustion boat), which is then put into a tube furnace under an argon atmosphere while the ventilation continues for 30 to 40 minutes. Firstly, it is heated from room temperature at a heating rate of 3 to 5° C./min to 500 to 550° C. which is maintained for 1 to 2 hours, and then heated to 800 to 900° C. from 500 to 550° C. at a heating rate of 3 to 5° C./min for sintering. After sintering, it is cooled to 300° C. from 800 to 900° C. at a cooling rate of 10° C./min, then cooled down naturally to room temperature, to give a black powder which is an ultra-thin carbon-layer composite material modified by nickel nanoclusters and vanadium carbide particles (Ni/VC@C composite material).

(18) Hereinafter, the present invention will be further described with the following examples. It should be understood that the following examples are used to explain this invention and do not mean to limit the scope of this invention. Any non-essential improvements and modifications made by a person skilled in the art based on this invention all fall into the protection scope of this invention. The specific process parameters below are only exemplary and are not restricted to the specific values shown below, that is a person skilled in the art can choose proper values within an appropriate range according to the description.

Example 1

(19) Nickel chloride hexahydrate, vanadium chloride and urea were mixed at a mole ratio of 0.5:1:1.56, and then added into 25 mL ultra-pure water and stirred for 15 minutes, to obtain solution A. The mixed solution A was put into a microwave apparatus to react for 4 hours at a temperature of 110° C. and a powder of 400 W, which was then cooled down to room temperature, cleaned by ultra-pure water and absolute ethanol for 3 times respectively, and then dried for 5 hours in a vacuum drying oven, to give a nickel vanadium double metal hydroxide.

(20) The nickel vanadium double metal hydroxide was treated with ultrasonic processing for 2 hours in an ethanol solution at a temperature of 60° C. and a power of 180 W, and then dried at room temperature to give precursor A.

(21) Dicyandiamide and the precursor A were mixed at a mass ratio of 2:1 and ground thoroughly for 30 minutes, to give a mixture of raw material.

(22) The mixture of raw material was put into a combustion boat, which was then put into a tube furnace under an argon atmosphere while the ventilation continued for 30 minutes. After that, it was heated from room temperature at a heating rate of 5° C./min to 500° C. which was maintained for 2 hours, and then heated from 500° C. at a heating rate of 5° C./min to 800° C. which was maintained for 2 hours. After that, it was cooled down to 300° C. from 800° C. at a cooling rate of 10° C./min, and then to room temperature via natural cooling, to give a black powder which is an ultra-thin carbon-layer composite material modified by nickel nanoclusters and vanadium carbide particles (Ni/VC@C composite material).

(23) As shown in FIG. 3, a transmission electron microscope image of the Ni/VC@C composite material obtained from example 1, the sample has a structure that vanadium carbide particles and nickel clusters are embedded in the ultra-thin carbon layer, and the thickness of the ultra-thin carbon layer is less than 10 nm. The metallic nickel clusters have a size of 3 to 8 nm (referring to the gray elliptical (or circular) dotted line in the figure, while the exposed crystal face of metal nickel is (111) crystal face, and the corresponding lattice pitch is 0.20 nm), vanadium carbide nanoparticles have a size of 3 to 5 nm (refer to the white elliptical (or circular) dotted line in the figure, while the exposed crystal face of vanadium carbide is (111) crystal face, and the corresponding lattice spacing is 0.24 nm).

Example 2

(24) Nickel chloride hexahydrate, vanadium chloride, and urea were mixed at a mole ratio of 1:1:1.56 and then added into 25 mL ultra-pure water and stirred for 15 minutes, to obtain solution A. The mixed solution A was put into a microwave apparatus to react for 4 hours at a temperature of 110° C. and a power of 400 W, which was then cooled down to room temperature, cleaned by ultra-pure water and absolute ethanol for 3 times respectively, and then dried for 5 hours in a vacuum drying oven, to give a nickel vanadium double metal hydroxide.

(25) The nickel vanadium double metal hydroxide was treated with ultrasonic processing for 2 hours in an ethanol solution at a temperature of 60° C. and a power of 180 W, and then dried at room temperature to give precursor A.

(26) Dicyandiamide and precursor A were mixed at a mass ratio of 4:1 and ground thoroughly for 30 minutes, to give a mixture of raw material.

(27) The mixture of raw material was put into a combustion boat, which was then put into a tube furnace under an argon atmosphere while the ventilation continued for 40 minutes. After that, it was heated from room temperature at a heating rate of 4° C./min to 500° C. which was maintained for 2 hours, and then heated from 500° C. at a heating rate of 4° C./min to 800° C. which was maintained for 2 hours. After that, it was cooled down to 300° C. from 800° C. at a cooling rate of 10° C./min, and then to room temperature via natural cooling, to give a black powder which is an ultra-thin carbon-layer composite material modified by nickel nanoclusters and vanadium carbide particles (Ni/VC@C composite material).

(28) As shown in FIG. 1, diffraction peaks of x-rays of the Ni/VC@C composite material obtained from Example 2 at 37.2°, 43.4°, 63.2° and 76.1° are totally matched with the crystal face of (111), (200), (220), and (311) of VC (JCPDS No. 73-0476) respectively, the diffraction peaks at 44.5° and 51.8° are the characteristic diffraction peaks of metallic nickel, and the diffraction peak at 24.6° is consistent with that of graphite carbon. These features indicate that vanadium carbide, nickel and graphitized carbon exist in the product. As shown in an X-ray photoelectron spectroscopy of N element represented in FIG. 2, the Ni/VC@C composite material obtained from example 2 has four forms of nitrogen: pyridinic N, pyrrolic N, oxidized N and Ni—NX bond. The presence of the Ni—NX bond can improve the hydrogen evolution activity of the samples. As shown in FIG. 4, a transmission electron microscope image of the Ni/VC@C composite material obtained from Example 2, the sample has a structure in which vanadium carbide particles and metallic nickel clusters are embedded in the ultra-thin carbon layer, and the thickness of the ultra-thin carbon layer is less than 10 nm. The metallic nickel clusters have a size of 6 to 10 nm (referring to the gray elliptical (or circular) dotted line in the figure, while the exposed crystal face of nickel is (111) crystal face, and the corresponding lattice pitch is 0.20 nm), and the vanadium carbide nanoparticles have a size of 3 to 8 nm (refer to the white elliptical (or circular) dotted line in the figure, while the exposed crystal face of vanadium carbide is (111) crystal face, and the corresponding lattice spacing is 0.24 nm). As shown in FIG. 6, the Ni/VC@C composite material obtained from Example 2 has a good electrocatalytic hydrogen evolution performance in 1 M KOH solution, and its overpotential is about 87 mV when the current density is 10 mA/cm.sup.2. As shown in FIG. 7, the Ni/VC@C composite material obtained from example 3 has a good electrocatalytic hydrogen evolution performance in 1 M PBS solution, and its overpotential is about 165 mV when the current density is 10 mA/cm.sup.2. As shown in FIG. 8, the Ni/VC@C composite material obtained from example 1 has a good electrocatalytic hydrogen evolution performance in 0.5 M H.sub.2SO.sub.4 solution, and its overpotential is about 140 mV when the current density is 10 mA/cm.sup.2. Under circumstances with the same current density, the lower the overpotential is, the better the activity is, so it can be seen that the samples obtained from the application have excellent electrocatalytic hydrogen production performance at a full range of pH values (0 to 14).

Example 3

(29) Nickel chloride hexahydrate, vanadium chloride and urea were mixed at a mole ratio of 1.5:1:1.56 and then added in 25 mL ultra-pure water and stirred for 15 minutes, to obtain solution A. The mixed solution A was put into a microwave apparatus to react for 4 hours at a temperature of 110° C. and a power of 400 W, which was then cooled down to room temperature, cleaned by ultra-pure water and absolute ethanol for 3 times respectively, and then dried for 5 hours in a vacuum drying oven, to give a nickel vanadium double metal hydroxide.

(30) The nickel vanadium double metal hydroxide was treated with ultrasonic processing for 2 hours in an ethanol solution at a temperature of 60° C. and a power of 180 W, and then dried at room temperature to give precursor A.

(31) Dicyandiamide and precursor A were mixed at a mass ratio of 3:1 and ground thoroughly for 30 minutes, to give a mixture of raw material.

(32) The mixture of raw material was put into a combustion boat, which was then put into a tube furnace under an argon atmosphere while the ventilation continued for 40 minutes. After that it was heated from room temperature at a heating rate of 5° C./min to 500° C. which was maintained for 2 hours, and heated from 500° C. at a heating rate of 5° C./min to 800° C. which was maintained for 2 hours. After that it was cooled down to 300° C. from 800° C. at a cooling rate of 10° C./min, and then to room temperature via natural cooling, to give a black powder which is an ultra-thin carbon-layer composite material modified by nickel nanoclusters and vanadium carbide particles (Ni/VC@C composite material). In the composite material, the thickness of the ultra-thin carbon layer is less than 10 nm, the nickel clusters have a size of 6 to 8 nm, and the vanadium carbide nanoparticles have a size of 3 to 5 nm.

Example 4

(33) Nickel chloride hexahydrate, vanadium chloride, and urea were mixed at a mole ratio of 2:1:1.56 and then added into 25 mL ultra-pure water and stirred for 15 minutes, to obtain solution A. The mixed solution A was put into a microwave apparatus to react for 4 hours at a temperature of 110° C. and a power of 300 W which was then cooled down to room temperature, cleaned by ultra-pure water and absolute ethanol for 3 times respectively, and then dried for 5 hours in a vacuum drying oven, to give a nickel vanadium double metal hydroxide.

(34) The nickel vanadium double metal hydroxide was treated with ultrasonic processing for 2 hours in an ethanol solution at a temperature of 70° C. and a power of 200 W, and then dried at room temperature to give the precursor A.

(35) Dicyandiamide and the precursor A were mixed at a mass ratio of 4:1 and ground thoroughly for 30 minutes, to give a mixture of raw material.

(36) The mixture of raw material was put into a combustion boat, which was then put into a tube furnace under an argon atmosphere while the ventilation continued for 40 minutes. After that, it was heated from room temperature at a heating rate of 5° C./min to 500° C. which was maintained for 2 hours, and then heated from 500° C. at a heating rate of 5° C./min to 800° C. which was maintained for 2 hours. After that, it was cooled down to 300° C. from 800° C. at a cooling rate of 10° C./min, and then to room temperature via natural cooling, to give a black powder which is an ultra-thin carbon-layer composite material modified by nickel nanoclusters and vanadium carbide particles (Ni/VC@C composite material). As shown in FIG. 5, a transmission electron microscope image of the Ni/VC@C composite material obtained from Example 4, the sample has a structure that vanadium carbide particle and metallic nickel cluster were embedded in the ultra-thin carbon layer, and the thickness of the ultra-thin carbon layer is less than 10 nm. The metallic nickel clusters have a size of 8 to 10 nm (referring to the gray elliptical (or circular) dotted line in the figure, at while the exposed crystal face of nickel is (111) crystal face, and the corresponding lattice pitch is 0.20 nm), and the vanadium carbides have a size of 3 to 8 nm (refer to the white elliptical (or circular) dotted line in the figure, at this time, the exposed crystal face of vanadium carbide is (111) crystal face, and the corresponding lattice spacing is 0.24 nm).

Example 5

(37) Nickel chloride hexahydrate, vanadium chloride and urea were mixed at a mole ratio of 1:1:1.56 and then added into 25 mL ultra-pure water and stirred for 15 minutes, to obtain solution A. The mixed solution A was put into a microwave apparatus to react for 4 hours at a temperature of 110° C. and a power of 400 W, which was then cooled down to room temperature, cleaned by ultra-pure water and absolute ethanol for 3 times respectively, and then dried for 5 hours in a vacuum drying oven, to give a nickel vanadium double metal hydroxide.

(38) The nickel vanadium double metal hydroxide was treated with ultrasonic processing for 2 hours in an ethanol solution at a temperature of 80° C. and a power of 190 W, and then dried at room temperature, to give the precursor A.

(39) Dicyandiamide and the precursor A were mixed at a mass ratio of 4:1 and ground thoroughly for 30 minutes, to a mixture of raw material.

(40) The mixture of raw material was put into a combustion boat, which was then put into a tube furnace with ultrasonic processing for 30 minutes. After that, it was heated from room temperature at a heating rate of 5° C./min to 500° C. which was maintained for 2 hours, and then heated from 500° C. at a heating rate of 5° C./min to 900° C. which was maintained for 2 hours. After that, it was cooled down to 300° C. from 900° C. at a cooling rate of 10° C./min, and then to room temperature via natural cooling, to give a black powder which is an ultra-thin carbon-layer composite material modified by nickel nanoclusters and vanadium carbide particles (Ni/VC@C composite material). In the composite material, the thickness of the ultra-thin carbon layer is less than 10 nm, and the nickel clusters have a size of 8 to 12 nm, and the vanadium carbide nanoparticles have a size of 6 to 8 nm.

(41) The embodiments given above are preferred examples for implementing the present invention, and the present invention is not limited to the above embodiments. Any non-essential additions and substitutions made by those skilled in the art based on the technical features of the technical solution of the present invention belong to the protection scope of the present invention.