Disclosure of Invention
The invention aims to provide a carbon-coated tungsten phosphide nanowire self-supporting structure composite material and a preparation method thereof, and aims to solve the problems of low conductivity, poor oxidation resistance and low electrocatalytic hydrogen evolution activity of the existing electrolyzed water catalyst.
The invention is realized by the following steps:
a carbon-coated tungsten phosphide nanowire self-supporting structure composite material specifically comprises: tungsten phosphide nanowires are uniformly grown on the surface of the substrate to form a self-supporting electrode structure, thin carbon layers are uniformly coated on the surfaces of the tungsten phosphide nanowires, and the thickness of the thin carbon layers is about 2 nm. The substrate can be selected from common substrate materials in the field, such as carbon fiber paper, foamed nickel, foamed copper, titanium sheet, etc., preferably, carbon fiber paper with the size of 2 × 5cm is selected2。
When the carbon-coated tungsten phosphide nanowire self-supporting structure composite material is used as an acidic electrolyzed water catalyst, the current density is 20mAcm-2In this case, the overpotential is 125 to 156mV, preferably 125 mV.
The preparation method of the carbon-coated tungsten phosphide nanowire self-supporting structure composite material comprises the following steps:
(a) loading a hydrated tungsten oxide nanowire precursor on a substrate;
(b) carrying out high-temperature annealing on the substrate-supported hydrated tungsten oxide nanowire precursor obtained in the step (a) in a tube furnace in an argon atmosphere, and injecting acetonitrile in the process to obtain a thin-layer carbon-coated tungsten oxide nanowire self-supporting composite structure;
(c) and (c) phosphorizing the surface of the thin-layer carbon-coated tungsten oxide nanowire self-supporting composite structure obtained in the step (b), so as to obtain the thin-layer carbon-coated tungsten phosphide nanowire self-supporting structure composite material.
In the step (a), a solvent thermal method is adopted, specifically, a hydrated tungsten oxide nanowire precursor is loaded on a substrate by the solvent thermal synthesis method, the solvent synthesis method can adopt reaction temperature and reaction time known to those skilled in the art, preferably, the reaction temperature is 150-200 ℃, and the reaction time is 12-20 h; more preferably, the reaction temperature is 180 ℃ and the reaction time is 16 h.
The hydrated tungsten oxide nanowire precursor can be synthesized by adopting known raw materials and solvents, preferably, an acidic solution containing tungsten ions is mixed with oxalic acid to obtain a transparent solution, and then ammonium sulfate is dissolved in the solution to obtain a final reaction solution.
Optionally, the acidic solution containing tungsten ions is a solution obtained by dissolving inorganic tungstate in deionized water and then adjusting the pH of the solution to 1.2, wherein the inorganic tungstate is sodium tungstate or ammonium tungstate.
Specifically, sodium tungstate dihydrate is used as a raw material, deionized water is used as a solvent, and the ratio of sodium tungstate dihydrate to deionized water is 2.5 mmol: 20mL of the solution is prepared, hydrochloric acid is added dropwise to adjust the pH value of the solution to 1.2, 7mmol of oxalic acid dihydrate is dissolved in the solution, the solution is diluted to 50mL, and finally 2.5g of ammonium sulfate is added to obtain a colorless transparent solution.
When the hydrated tungsten oxide nanowire precursor is loaded on the substrate, the obtained reaction liquid is transferred into a reaction container, the substrate is placed obliquely close to the wall, and a hydrothermal synthesis reaction is carried out at a set temperature.
In the step (b), the sample obtained in the step (a) is placed in a tube furnace, and the temperature is raised to 600 ℃ under an argon atmosphere (heating rate: 5 ℃ C. for min)-1) And acetonitrile was injected. The reaction temperature for injecting acetonitrile is preferably 600 ℃, and the injection rate is 5mLh-1The injection time is 2 h.
In the step (c), the sample obtained in the step (b) is phosphated by adopting a high-temperature phosphating method, specifically, 2g of sodium hypophosphite is placed in a ceramic boat on the upstream side of the tube furnace, and the sample obtained in the step (b) is placed in the ceramic boat in the middle of the tube furnace. And carrying out high-temperature phosphorization under an argon atmosphere. The temperature of the sodium phosphite position is 350 ℃, the phosphorization temperature of the sample position is 700-900 ℃, and the phosphorization time is 60-180 min.
The invention combines hydrothermal reaction, organic matter high-temperature pyrolysis reaction and phosphorization reaction to prepare the thin-layer carbon-coated tungsten phosphide nanowire composite structure in one step. The introduction of the surface thin-layer carbon can improve the surface oxidation resistance of the material, thereby improving the chemical stability of the material. Meanwhile, the coating effect of the thin-layer carbon on the surface of the tungsten phosphide can improve the electronic structure of the composite system, so that the electrocatalytic hydrogen evolution activity of the composite system is enhanced. The composite material has obvious advantages in the aspects of chemical stability and electrocatalytic activity and has considerable application prospect, which does not appear in previous reports.
The preparation process of the composite material is simple, easy to operate, low in cost and easy to carry out large-scale production, and has the potential of large-scale application for the development of industrial electrolyzed water catalysts.
Detailed Description
The invention is further illustrated by the following examples, which are given by way of illustration only and are not intended to limit the scope of the invention in any way.
Procedures and methods not described in detail in the following examples are conventional methods well known in the art, and the reagents used in the examples are either analytically or chemically pure and are either commercially available or prepared by methods well known to those of ordinary skill in the art. The following examples all achieve the objects of the present invention.
Example 1
Dissolving 2.5mmol of sodium tungstate dihydrate in 20mL of deionized water to obtain a colorless transparent solution, dropwise adding hydrochloric acid to adjust the pH value of the solution to 1.2 to obtain a light yellow solution, then adding 7mmol of oxalic acid dihydrate into the solution, diluting the solution to 50mL, and adding 2.5g of ammonium sulfate to obtain a colorless transparent solution. Transferring the mixed solution into a reaction kettle, and simultaneously transferring carbon fiber paper (2 multiplied by 5 cm)2) Placing the carbon fiber paper obliquely against the wall, heating to 180 ℃, reacting for 16h, then naturally cooling, taking out the carbon fiber paper, washing the carbon fiber paper with deionized water, and drying in vacuum at 60 ℃ for 12 h. The sample was placed in a tube furnace under argon (flow rate 60sccm) at 5 ℃ for min-1Heating to 600 deg.C, and then using a syringe pump at 600 deg.CMixing acetonitrile 5mLh-1The mixture is injected into equipment at a constant feeding rate, the heat preservation time is 120min, and then the mixture is naturally cooled to room temperature, so that the thin-layer carbon-coated carbon fiber paper loaded tungsten oxide nanowire self-supporting structure composite material is obtained.
The sample obtained above and 2g of sodium hypophosphite were placed in a two-temperature zone tube furnace, with the sodium hypophosphite placed on the upstream side of the tube furnace. The tube furnace was then heated under argon atmosphere with the sample position at 5 ℃ for min-1The temperature is raised to 800 ℃, the sodium hypophosphite position is raised to 350 ℃ in the same time, and the temperature is kept for 120 min. And finally, automatically cooling the tube furnace to room temperature to obtain the thin-layer carbon-coated tungsten phosphide nanowire/carbon fiber paper self-supporting structure composite material.
The prepared material is characterized, and the obtained result is shown in figures 1-3. As can be seen from figure 1, the tungsten phosphide phase in the prepared thin-layer carbon-coated tungsten phosphide nanowire/carbon fiber paper self-supporting structure composite material is matched with WP29-1364 of JCPDS card. As can be seen from fig. 2, the obtained composite material is uniformly loaded on the carbon fiber paper, and the composite material is in a nanowire structure. As can be seen from FIG. 3, the surface of the tungsten phosphide nanowire is uniformly coated with a thin carbon shell, and the thickness of the thin carbon shell is about 2 nm.
Comparative example 1
Dissolving 2.5mmol of sodium tungstate dihydrate in 20mL of deionized water to obtain a colorless transparent solution, dropwise adding hydrochloric acid to adjust the pH value of the solution to 1.2 to obtain a light yellow solution, then adding 7mmol of oxalic acid dihydrate into the solution, diluting the solution to 50mL, and adding 2.5g of ammonium sulfate to obtain a colorless transparent solution. Transferring the mixed solution into a reaction kettle, and simultaneously transferring carbon fiber paper (2 multiplied by 5 cm)2) Placing the carbon fiber paper obliquely against the wall, heating to 180 ℃, reacting for 16h, then naturally cooling, taking out the carbon fiber paper, washing the carbon fiber paper with deionized water, and drying in vacuum at 60 ℃ for 12 h. The sample was placed in a tube furnace under argon (flow rate 60sccm) at 5 ℃ for min-1And heating to 600 ℃, keeping the temperature for 120min, and then naturally cooling to room temperature to obtain the carbon fiber paper loaded tungsten oxide nanowire self-supporting structure composite material.
The sample obtained above was mixed with 2g of sodium hypophosphitePlacing in a two-temperature zone tubular furnace, wherein the sodium hypophosphite is placed on the upstream side of the tubular furnace. The tube furnace was then heated under argon atmosphere with the sample position at 5 ℃ for min-1The temperature is raised to 800 ℃, the sodium hypophosphite position is raised to 350 ℃ in the same time, and the temperature is kept for 120 min. And finally, automatically cooling the tube furnace to room temperature to obtain the tungsten phosphide nanowire/carbon fiber paper self-supporting structure composite material.
Example 2
Dissolving 2.5mmol of sodium tungstate dihydrate in 20mL of deionized water to obtain a colorless transparent solution, dropwise adding hydrochloric acid to adjust the pH value of the solution to 1.2 to obtain a light yellow solution, then adding 7mmol of oxalic acid dihydrate into the solution, diluting the solution to 50mL, and adding 2.5g of ammonium sulfate to obtain a colorless transparent solution. Transferring the mixed solution into a reaction kettle, and simultaneously, adding a titanium sheet (2 multiplied by 5 cm)2) Placing the titanium plate obliquely close to the wall, heating to 180 ℃, reacting for 16h, then naturally cooling, taking out the titanium plate, washing the titanium plate by using deionized water, and drying in vacuum at 60 ℃ for 12 h. The sample was placed in a tube furnace under argon (flow rate 60sccm) at 5 ℃ for min-1The temperature was raised to 600 ℃ and then acetonitrile was pumped at 600 ℃ using a syringe pump at 5mLh-1The mixture is injected into equipment at a constant feeding rate, the heat preservation time is 120min, and then the mixture is naturally cooled to room temperature, so that the thin-layer carbon-coated titanium plate loaded tungsten oxide nanowire self-supporting structure composite material is obtained.
The sample obtained above and 2g of sodium hypophosphite were placed in a two-temperature zone tube furnace, with the sodium hypophosphite placed on the upstream side of the tube furnace. The tube furnace was then heated under argon atmosphere with the sample position at 5 ℃ for min-1The temperature is raised to 800 ℃, the sodium hypophosphite position is raised to 350 ℃ in the same time, and the temperature is kept for 120 min. And finally, automatically cooling the tube furnace to room temperature to obtain the thin-layer carbon-coated tungsten phosphide nanowire/titanium sheet self-supporting structure composite material. The Raman test was performed on the obtained samples, and the obtained results are shown in fig. 4.
Example 3
Dissolving 2.5mmol sodium tungstate dihydrate in 20mL deionized water to obtain colorless transparent solution, dropwise adding hydrochloric acid to adjust the pH value of the solution to 1.2 to obtain light yellow solution,then, 7mmol of oxalic acid dihydrate was added to the above solution, and the solution was diluted to 50mL, and 2.5g of ammonium sulfate was added to obtain a colorless transparent solution. Transferring the mixed solution into a reaction kettle, and simultaneously transferring carbon fiber paper (2 multiplied by 5 cm)2) Placing the carbon fiber paper obliquely against the wall, heating to 180 ℃, reacting for 16h, then naturally cooling, taking out the carbon fiber paper, washing the carbon fiber paper with deionized water, and drying in vacuum at 60 ℃ for 12 h. The sample was placed in a tube furnace under argon (flow rate 60sccm) at 5 ℃ for min-1The temperature was raised to 600 ℃ and then acetonitrile was pumped at 600 ℃ using a syringe pump at 5mLh-1The mixture is injected into equipment at a constant feeding rate, the heat preservation time is 120min, and then the mixture is naturally cooled to room temperature, so that the thin-layer carbon-coated carbon fiber paper loaded tungsten oxide nanowire self-supporting structure composite material is obtained.
The sample obtained above and 2g of sodium hypophosphite were placed in a two-temperature zone tube furnace, with the sodium hypophosphite placed on the upstream side of the tube furnace. The tube furnace was then heated under argon atmosphere with the sample position at 5 ℃ for min-1The temperature is raised to 700 ℃, the sodium hypophosphite position is raised to 350 ℃ in the same time, and the temperature is kept for 120 min. And finally, automatically cooling the tube furnace to room temperature to obtain the thin-layer carbon-coated tungsten phosphide nanowire/carbon fiber paper self-supporting structure composite material.
Example 4
Dissolving 2.5mmol of sodium tungstate dihydrate in 20mL of deionized water to obtain a colorless transparent solution, dropwise adding hydrochloric acid to adjust the pH value of the solution to 1.2 to obtain a light yellow solution, then adding 7mmol of oxalic acid dihydrate into the solution, diluting the solution to 50mL, and adding 2.5g of ammonium sulfate to obtain a colorless transparent solution. Transferring the mixed solution into a reaction kettle, and simultaneously transferring carbon fiber paper (2 multiplied by 5 cm)2) Placing the carbon fiber paper obliquely against the wall, heating to 180 ℃, reacting for 16h, then naturally cooling, taking out the carbon fiber paper, washing the carbon fiber paper with deionized water, and drying in vacuum at 60 ℃ for 12 h. The sample was placed in a tube furnace under argon (flow rate 60sccm) at 5 ℃ for min-1The temperature was raised to 600 ℃ and then acetonitrile was pumped at 600 ℃ using a syringe pump at 5mLh-1The constant feeding speed is injected into the equipment, the heat preservation time is 120min, and then the carbon fiber paper is naturally cooled to the room temperature to obtain the thin-layer carbon-coated carbon fiber paper loaded tungsten oxideThe nanowire self-supporting structural composite material.
The sample obtained above and 2g of sodium hypophosphite were placed in a two-temperature zone tube furnace, with the sodium hypophosphite placed on the upstream side of the tube furnace. The tube furnace was then heated under argon atmosphere with the sample position at 5 ℃ for min-1The temperature is raised to 900 ℃, the sodium hypophosphite position is raised to 350 ℃ in the same time, and the temperature is kept for 120 min. And finally, automatically cooling the tube furnace to room temperature to obtain the thin-layer carbon-coated tungsten phosphide nanowire/carbon fiber paper self-supporting structure composite material.
Example 5
Dissolving 2.5mmol of sodium tungstate dihydrate in 20mL of deionized water to obtain a colorless transparent solution, dropwise adding hydrochloric acid to adjust the pH value of the solution to 1.2 to obtain a light yellow solution, then adding 7mmol of oxalic acid dihydrate into the solution, diluting the solution to 50mL, and adding 2.5g of ammonium sulfate to obtain a colorless transparent solution. Transferring the mixed solution into a reaction kettle, and simultaneously transferring carbon fiber paper (2 multiplied by 5 cm)2) Placing the carbon fiber paper obliquely against the wall, heating to 180 ℃, reacting for 12h, then naturally cooling, taking out the carbon fiber paper, washing the carbon fiber paper with deionized water, and drying in vacuum at 60 ℃ for 12 h. The sample was placed in a tube furnace under argon (flow rate 60sccm) at 5 ℃ for min-1The temperature was raised to 600 ℃ and then acetonitrile was pumped at 600 ℃ using a syringe pump at 5mLh-1The mixture is injected into equipment at a constant feeding rate, the heat preservation time is 120min, and then the mixture is naturally cooled to room temperature, so that the thin-layer carbon-coated carbon fiber paper loaded tungsten oxide nanowire self-supporting structure composite material is obtained.
The sample obtained above and 2g of sodium hypophosphite were placed in a two-temperature zone tube furnace, with the sodium hypophosphite placed on the upstream side of the tube furnace. The tube furnace was then heated under argon atmosphere with the sample position at 5 ℃ for min-1The temperature is raised to 800 ℃, the sodium hypophosphite position is raised to 350 ℃ in the same time, and the temperature is kept for 120 min. And finally, automatically cooling the tube furnace to room temperature to obtain the thin-layer carbon-coated tungsten phosphide nanowire/carbon fiber paper self-supporting structure composite material.
Example 6
2.5mmol of sodium tungstate dihydrate is dissolved in 20mL to be separatedObtaining a colorless transparent solution in water, dropwise adding hydrochloric acid to adjust the pH value of the solution to 1.2 to obtain a light yellow solution, then adding 7mmol of oxalic acid dihydrate into the solution, diluting the solution to 50mL, and adding 2.5g of ammonium sulfate to obtain a colorless transparent solution. Transferring the mixed solution into a reaction kettle, and simultaneously transferring carbon fiber paper (2 multiplied by 5 cm)2) Placing the carbon fiber paper obliquely against the wall, heating to 180 ℃, reacting for 20h, then naturally cooling, taking out the carbon fiber paper, washing the carbon fiber paper with deionized water, and drying in vacuum at 60 ℃ for 12 h. The sample was placed in a tube furnace under argon (flow rate 60sccm) at 5 ℃ for min-1The temperature was raised to 600 ℃ and then acetonitrile was pumped at 600 ℃ using a syringe pump at 5mLh-1The mixture is injected into equipment at a constant feeding rate, the heat preservation time is 120min, and then the mixture is naturally cooled to room temperature, so that the thin-layer carbon-coated carbon fiber paper loaded tungsten oxide nanowire self-supporting structure composite material is obtained.
The sample obtained above and 2g of sodium hypophosphite were placed in a two-temperature zone tube furnace, with the sodium hypophosphite placed on the upstream side of the tube furnace. The tube furnace was then heated under argon atmosphere with the sample position at 5 ℃ for min-1The temperature is raised to 800 ℃, the sodium hypophosphite position is raised to 350 ℃ in the same time, and the temperature is kept for 120 min. And finally, automatically cooling the tube furnace to room temperature to obtain the thin-layer carbon-coated tungsten phosphide nanowire/carbon fiber paper self-supporting structure composite material.
Example 7
Dissolving 2.5mmol of sodium tungstate dihydrate in 20mL of deionized water to obtain a colorless transparent solution, dropwise adding hydrochloric acid to adjust the pH value of the solution to 1.2 to obtain a light yellow solution, then adding 7mmol of oxalic acid dihydrate into the solution, diluting the solution to 50mL, and adding 2.5g of ammonium sulfate to obtain a colorless transparent solution. Transferring the mixed solution into a reaction kettle, and simultaneously transferring carbon fiber paper (2 multiplied by 5 cm)2) Placing the carbon fiber paper obliquely against the wall, heating to 180 ℃, reacting for 16h, then naturally cooling, taking out the carbon fiber paper, washing the carbon fiber paper with deionized water, and drying in vacuum at 60 ℃ for 12 h. The sample was placed in a tube furnace under argon (flow rate 60sccm) at 5 ℃ for min-1The temperature was raised to 600 ℃ and then acetonitrile was pumped at 600 ℃ using a syringe pump at 5mLh-1Constant feed rate injection apparatus ofAnd (4) the temperature is 120min, and then the carbon fiber paper is naturally cooled to room temperature to obtain the thin-layer carbon-coated carbon fiber paper loaded tungsten oxide nanowire self-supporting structure composite material.
The sample obtained above and 2g of sodium hypophosphite were placed in a two-temperature zone tube furnace, with the sodium hypophosphite placed on the upstream side of the tube furnace. The tube furnace was then heated under argon atmosphere with the sample position at 5 ℃ for min-1The temperature is raised to 800 ℃, the sodium hypophosphite position is raised to 350 ℃ in the same time, and the temperature is kept for 60 min. And finally, automatically cooling the tube furnace to room temperature to obtain the thin-layer carbon-coated tungsten phosphide nanowire/carbon fiber paper self-supporting structure composite material.
Example 8
Dissolving 2.5mmol of sodium tungstate dihydrate in 20mL of deionized water to obtain a colorless transparent solution, dropwise adding hydrochloric acid to adjust the pH value of the solution to 1.2 to obtain a light yellow solution, then adding 7mmol of oxalic acid dihydrate into the solution, diluting the solution to 50mL, and adding 2.5g of ammonium sulfate to obtain a colorless transparent solution. Transferring the mixed solution into a reaction kettle, and simultaneously transferring carbon fiber paper (2 multiplied by 5 cm)2) Placing the carbon fiber paper obliquely against the wall, heating to 180 ℃, reacting for 16h, then naturally cooling, taking out the carbon fiber paper, washing the carbon fiber paper with deionized water, and drying in vacuum at 60 ℃ for 12 h. The sample was placed in a tube furnace under argon (flow rate 60sccm) at 5 ℃ for min-1And (3) heating to 600 ℃, injecting acetonitrile into equipment at 600 ℃ by using an injection pump at a constant feeding rate of 5mLh-1, keeping the temperature for 120min, and naturally cooling to room temperature to obtain the thin-layer carbon-coated carbon fiber paper loaded tungsten oxide nanowire self-supporting structure composite material.
The sample obtained above and 2g of sodium hypophosphite were placed in a two-temperature zone tube furnace, with the sodium hypophosphite placed on the upstream side of the tube furnace. The tube furnace was then heated under argon atmosphere with the sample position at 5 ℃ for min-1The temperature is raised to 800 ℃, the sodium hypophosphite position is raised to 350 ℃ in the same time, and the temperature is kept for 180 min. And finally, automatically cooling the tube furnace to room temperature to obtain the thin-layer carbon-coated tungsten phosphide nanowire/carbon fiber paper self-supporting structure composite material.
Example 9
The thin-layer carbon-coated tungsten phosphide nanowire composite material prepared in examples 1 and 3-8 and the carbon fiber paper-supported tungsten phosphide nanowire material prepared in comparative example 1 were used for acidic electrocatalytic hydrogen evolution. The samples were electrochemically characterized using an electrochemical workstation and measured using a three-electrode system. Wherein, a mercury/mercurous sulfate electrode is used as a reference electrode, a carbon fiber paper loaded thin-layer carbon-coated tungsten phosphide nanowire composite material or a carbon fiber paper loaded tungsten phosphide nanowire material is used as a working electrode, and 0.5MH is used2SO4As an electrolyte. The electrochemical performance of the materials prepared in examples 1, 3-8 and comparative example 1 is characterized by scanning the polarization curve, and the scanning speed is 5mVs-1The test potential is converted into a standard hydrogen electrode potential.
The obtained results are shown in fig. 5, and it can be seen from the figure that compared with the carbon fiber paper-supported tungsten phosphide nanowire material prepared in comparative example 1, the carbon fiber paper-supported thin-layer carbon-coated tungsten phosphide nanowire composite materials obtained in examples 1, 3-8 have excellent electrocatalytic hydrogen production performance, especially when the current density is 20mA/cm2The minimum overpotential is 125 mV. Therefore, the carbon fiber paper loaded thin-layer carbon-coated tungsten phosphide nanowire composite material with excellent electro-catalytic performance can be directly prepared by the method.