CN108203095A - A kind of tungsten carbide nano-array material, preparation method and the usage - Google Patents

Abstract

The invention discloses a tungsten carbide nano-array material, which comprises a base material and a tungsten carbide nano-array structure material grown on the base material, and the tungsten carbide nano-array structure material can be nitrogen-doped or non-nitrogen-doped; the Tungsten carbide nano-array structures include nano-wire arrays, nano-belt arrays, nano-pillar arrays or nano-web arrays. The invention also discloses the preparation method of the tungsten carbide nano-array material and the application of electrocatalyzing hydrogen and oxygen evolution and high-efficiency photothermal evaporation for water purification.

Description

A kind of tungsten carbide nano-array material, its preparation method and application

technical field

The invention belongs to the field of preparation and utilization of inorganic nanometer materials, and in particular relates to a tungsten carbide nanoarray material, its preparation method and application.

Background technique

Tungsten carbide (WC) is cheap and often used in the preparation of hard metals with stable properties. In air, it is stable below 400°C. Tungsten carbide has good electrical and thermal conductivity. Studies have shown that tungsten carbide has a plasma resonance effect and is resistant to laser irradiation. Tungsten carbide is very stable in acidic systems, and has catalytic hydrogenolysis similar to platinum, which can be extended to many fields of organic catalysis and electrocatalysis. The above characteristics have made the research of tungsten carbide materials widely concerned, and tungsten carbide materials are increasingly used in the fields of production, life and military industry.

However, the preparation of tungsten carbide nanomaterials faces many problems. First, at present, tungsten carbide nanomaterials are mostly powder materials. However, powder materials need to be redispersed, sintered, sprayed, etc. in practical applications, and the sprayed tungsten carbide materials cannot be in good contact with the substrate, which will cause disadvantages in the application. Influence, for example, will affect the specific surface area, hardness, conductivity, etc. of the material after forming. Second, the preparation of tungsten carbide requires a high-temperature carbonization process, which mostly uses a mixture of hydrogen and methane as a carbon source, which makes the production process more dangerous. Third, it is reported that the tungsten carbide nanopowder materials produced by the synthesis method that does not use hydrogen and methane as carbon sources mostly have complex tungsten and carbon compound components.

In order to solve the above-mentioned problems, the present invention has been proposed.

Contents of the invention

The invention belongs to the fields of preparation of inorganic nanomaterials and energy conversion and utilization, and specifically relates to the preparation of tungsten carbide nanoarray materials by hydrothermal method and volatile solid vapor phase chemical deposition method. The tungsten carbide nanoarray materials prepared by this method can be applied to acidic systems Electrocatalytic hydrogen evolution and electrocatalytic oxygen evolution can also be applied to photothermal evaporation of water such as brine desalination and sewage treatment.

The first aspect of the present invention relates to a tungsten carbide nano-array material, which is characterized in that it includes a base material and a tungsten carbide nano-array structure material grown on the base material. The array is an orderly arrangement of structurally similar units.

The tungsten carbide nano-array structure material can be nitrogen-doped or non-nitrogen-doped. When it is a nitrogen-doped tungsten carbide nano-array structure material, generally the nitrogen element accounts for 0.01-20 wt% of the tungsten carbide nano-array structure material.

Preferably, the base material can be used as long as it is stable in a synthetic environment, and the base material in the present invention is one or more of metal, quartz glass, silicon, ceramic or carbon material.

Preferably, the tungsten carbide nanoarray structure material has only the characteristic peaks of the substrate, the characteristic peaks of carbon and the characteristic peaks of tungsten carbide in the XRD pattern, and the nitrogen-doped tungsten carbide nanoarray structure material also only has the characteristic peaks of the substrate, carbon The characteristic peaks of tungsten carbide and the characteristic peaks of tungsten carbide.

Preferably, the tungsten carbide nanoarrays include nanowire arrays, nanoribbon arrays, nanocolumnar arrays or nanoweb arrays.

The second aspect of the present invention relates to a method for preparing a tungsten carbide nano-array material, comprising the following steps:

(1) Add a pH adjuster and a shape adjuster to the tungsten-containing solution, and then add the base material, keep at 120°C-200°C for 0.5-20h, and cool to obtain a tungsten oxide nano-array material.

(2) keeping the tungsten oxide nano-array material obtained in step (1) together with a carbon source at 800°C-950°C under inert gas conditions for 0.5-3h to obtain the tungsten carbide nano-array material.

In a preferred embodiment of the second aspect of the present invention, the tungsten-containing solution described in step (1) is one or more of tungstic acid solution, ammonium tungstate solution, sodium tungstate solution, and tungsten chloride solution.

Preferably, the pH regulator is one or more of acid, alkali, salt, and oxide, and may be, but not limited to, one or more of sulfuric acid, hydrochloric acid, phosphoric acid, sodium hydroxide, and potassium hydroxide. The shape modifier is a variety of salts that are easily soluble in the corresponding solution and will not precipitate out during the reaction, which can be but not limited to sodium sulfate, potassium sulfate, sodium chloride, potassium chloride, ammonium sulfate or chlorine One or several ammonium chlorides.

Preferably, the base material in step (1) is one or more of metal, quartz glass, silicon, ceramic or carbon material.

Preferably, the carbon source described in step (2) is one or more of melamine, dicyandiamide, and terpenes, and the terpenes are one or more of camphor, myrcene, and citral. As long as the solid powder is thermally volatile and contains carbon, oxygen, hydrogen and other elements, it can be used as the carbon source of the present invention; when the carbon source contains nitrogen, a small amount of nitrogen will be doped in the tungsten carbide nanoarray material, but Does not affect the phase type of tungsten carbide.

The third aspect of the present invention relates to the use of the tungsten carbide nano-array material for photothermal evaporation of water (such as brine desalination, sewage treatment) or electrocatalytic hydrogen evolution or electrocatalytic oxygen evolution under acidic conditions.

Beneficial effects of the present invention:

(1) The appearance of the tungsten carbide nano-array material of the present invention is novel, which is disclosed for the first time. Tungsten carbide has very good light absorption properties. This is related to the anti-reflection effect of the nano-array structure, the light absorption characteristics of tungsten carbide itself and the plasmon resonance effect. The light absorption performance of the tungsten carbide nano-array material of the invention is greater than 98% in the whole solar spectrum range. The comparison between the spectral absorption of the tungsten carbide nano-array material of the present invention and the spectral absorption of nano-graphite is shown in FIG. 12 .

(2) The tungsten carbide nano-array material of the present invention uses volatile solids as the carbon source, which improves the safety of the tungsten carbide synthesis method using hydrogen and methane as the carbon source. When the carbon source contains nitrogen, nitrogen doping can also be obtained in the tungsten carbide nano-array material, and the nitrogen doping does not affect the properties of the pure phase of the tungsten carbide nano-array material at all.

(3) The tungsten carbide nanoarray material of the present invention, especially the tungsten carbide nanoarray material doped with nitrogen, has excellent performance as a catalyst for electrocatalyzing hydrogen and oxygen evolution under acidic conditions. Compared with precious metals, the cost is low, and it is efficient and stable compared with non-precious metals.

(4) The tungsten carbide nanoarray material of the present invention can be used for the production of hydrogen, the treatment of acid-containing waste liquid, and the photothermal evaporation of water such as brine desalination, sewage treatment, etc., with high efficiency, stability and excellent performance.

Description of drawings

Fig. 1 is the scanning electron micrograph of the tungsten carbide nanowire array of the present invention;

Fig. 2 is the scanning electron micrograph of the tungsten carbide nanoribbon array of the present invention;

Fig. 3 is the scanning electron micrograph of the tungsten carbide nano columnar array of the present invention;

Fig. 4 is the scanning electron micrograph of the tungsten carbide nano webbed array of the present invention;

Fig. 5 is the XRD spectrum of the tungsten carbide nano-array based on carbon fiber paper of the present invention;

Figure 6 is a scanning electron micrograph of the tungsten oxide nanoribbon array of the present invention;

Fig. 7 is the HER linear scanning polarization curve of the tungsten carbide nanoarray material of the present invention compared with platinum carbon;

Figure 8 is the stability test curves of the tungsten carbide nanoarray material of the present invention catalyzing HER at current densities of 20mA cm ^-2 and 50mA cm ^-2 ;

Fig. 9 is the stability test curve of the tungsten carbide nanoarray material of the present invention catalyzing HER at a current density of 60mA cm ^-2 ;

Figure 10 is the stability test curve of the tungsten carbide nano-array material of the present invention catalyzing HER at a current density of 100mA cm ^-2 ;

Fig. 11 is the OER polarization curve of the tungsten carbide nano-array material of the present invention compared with iridium oxide and iridium carbon catalyst;

Fig. 12 is a comparison diagram of the spectral absorption of the tungsten carbide nano-array material of the present invention and the spectral absorption of nano-graphite;

Fig. 13 is a graph comparing the water evaporation of the tungsten carbide nano-array material of the present invention with the water evaporation on the surface of nano-graphite, and the rate curve of water surface evaporation;

Fig. 14 is a comparison chart of ion concentrations before and after seawater and sewage are treated by photothermal evaporation of the tungsten carbide nanoarray material of the present invention.

Detailed ways

The present invention is further described below in conjunction with embodiment. It should be noted that the examples are not intended to limit the protection scope of the present invention, and those skilled in the art understand that any improvements and changes made on the basis of the present invention are within the protection scope of the present invention.

The chemical reagents used in the following examples are all conventional reagents, all of which are commercially available. The base materials in this embodiment are all carbon fiber papers, and the same effect can also be obtained by using other base materials such as metal, quartz glass, silicon, ceramics, and the like.

Example 1

Dissolve 0.6g of sodium tungstate in 20ml of water to form a uniform solution. Then, add 100 μl of sulfuric acid and 0.2 g of anhydrous sodium sulfate to the solution and mix well, put it into the polytetrafluoroethylene liner of the reaction kettle, add carbon fiber paper base to the polytetrafluoroethylene liner, seal the liner, and seal the reaction Kettle, hydrothermal reaction at 200°C for 18 hours, then cooled and samples were taken out. The carbon fiber paper-based tungsten oxide nano-array material is obtained.

Put 2 g of camphor and the above-mentioned carbon fiber paper-based tungsten oxide nanoarray material into a tube furnace, protect with argon, react at 950° C. for 2 hours, cool down naturally and take out the samples. The tungsten carbide nanowire array material is obtained, as shown in FIG. 1 .

FIG. 5 is an XRD spectrum of a tungsten carbide nanoarray based on carbon fiber paper. It can be seen from the spectrum that there are only the characteristic peaks of the base carbon fiber paper, the characteristic peaks of carbon and the characteristic peaks of WC.

Example 2

Dissolve 0.5g of tungsten chloride in 20ml of water to make a uniform solution. Then, add 115μl hydrochloric acid and 0.2g potassium chloride to the solution and mix well, put it into the polytetrafluoroethylene liner of the reaction kettle, add carbon fiber paper base to the polytetrafluoroethylene liner, seal the inner liner, and seal the reaction kettle , reacted at 180 °C for 12 hours, then cooled and took out the sample. The carbon fiber paper-based tungsten oxide nano-array material was obtained, and the scanning electron microscope of the obtained sample is shown in FIG. 6 .

Put 2 g of melamine and the above-mentioned carbon fiber paper-based tungsten oxide nanoarray material into a tube furnace, protect with argon, react at 850° C. for 3 hours, cool down naturally and take out samples. The tungsten carbide nanoribbon array material is obtained, as shown in FIG. 2 . The material obtained in this embodiment is a nitrogen-doped tungsten carbide nano-array material.

Example 3

Dissolve 0.9g of potassium tungstate in 20ml of water to form a uniform solution. Then, add 200 μl of hydrochloric acid and 0.2 g of potassium sulfate to the solution and mix evenly, put it into the polytetrafluoroethylene liner of the reaction kettle, add carbon fiber paper base to the polytetrafluoroethylene liner, seal the inner bag, and seal the reaction kettle. React at 180°C for 12 hours, then cool and take out a sample. The carbon fiber paper-based tungsten oxide nano-array material is obtained.

Put 2g of dicyandiamide and the above-mentioned carbon fiber paper-based tungsten oxide nanoarray material in a tube furnace, protect with argon, react at 800°C for 1 hour, cool down naturally and take out the sample. The tungsten carbide nano-pillar array material is obtained, as shown in FIG. 3 . The material obtained in this embodiment is a nitrogen-doped tungsten carbide nano-array material.

Example 4

Dissolve 0.3g of sodium tungstate in 20ml of water to form a uniform solution. Then, add 100 μl of phosphoric acid and 0.1 g of sodium chloride to the solution and mix evenly, put it into the polytetrafluoroethylene liner of the reaction kettle, add carbon fiber paper base to the polytetrafluoroethylene liner, seal the inner liner, and seal the reaction kettle , reacted at 180 °C for 6 hours, then cooled and took out the sample. The carbon fiber paper-based tungsten oxide nano-array material is obtained.

Put 2g of dicyandiamide and the above-mentioned carbon fiber paper-based tungsten oxide nanoarray material into a tube furnace, protect with argon, react at 850°C for 2 hours, cool down naturally and take out the samples. The tungsten carbide nano-webbed array material is obtained, as shown in FIG. 4 . The material obtained in this embodiment is a nitrogen-doped tungsten carbide nano-array material.

Example 5

Electrocatalytic hydrogen evolution reaction (HER) test.

The sulfuric acid solution of 0.5M is selected as the electrolyte, and a standard three-electrode system is used for testing, wherein the working electrode is the tungsten carbide nano-array material in Example 2, the auxiliary electrode is a carbon rod, and the reference electrode is silver/silver chloride reference electrode. than the electrode. When the current densities are 10mA cm ^-2 and 200mA cm ^-2 respectively, the overpotentials are only 89mV and 190mV respectively (as shown in Figure 7), which shows the high efficiency of the material.

When the current density is about 20mA cm ^-2 , 50mA cm ^-2 (as shown in Figure 8), 60mA cm ^-2 (as shown in Figure 9), and 100mA cm ^-2 (as shown in Figure 10), the working time is 10 The hourly current density changes were +2.9%, -1.9%, -0.5% and +1.1%, indicating that the stability of the material is very high.

Example 6

Electrocatalytic oxygen evolution reaction (OER) test.

Select 0.5M sulfuric acid solution as the electrolyte, and use a standard three-electrode system to test, wherein the working electrode is the tungsten carbide nanoarray material in Example 3, the auxiliary electrode is a platinum electrode, and the reference electrode is a silver/silver chloride reference electrode. than the electrode. Its peak potential is around 1.4V vs. RHE, and when the potential reaches 1.7V vs. RHE, its current density can reach 60mAcm ^-2 (as shown in Figure 11). It shows that the tungsten carbide nanoarray material in Example 3 has efficient OER performance under acidic conditions.

Example 7

Laboratory tests for water evaporation rate.

The device for testing the evaporation rate of water in the laboratory is used. The light source used is a xenon lamp light source, and the light condition is AM1.5, which is the light condition of ordinary atmospheric environment. Using the tungsten carbide nano-web array material in Example 4, the rate curves compared with the water evaporation on the nano-graphite surface and the water surface evaporation are shown in FIG. 13 . It can be seen from Figure 13 that the evaporation rate of water on the surface of tungsten carbide nanoarrays is 1.25 times that of the surface of nano-graphite, and 1.89 times that of the surface of ordinary water. Therefore, the tungsten carbide nanoarray material can effectively promote the evaporation of water.

Example 8

Tungsten carbide nano-array materials are used for salt water desalination and sewage treatment.

Apparatus for purifying brine using laboratory water evaporation. The brine and sewage are stored in the "storage tank" and can be replenished through the water inlet, and the liquid level is controlled through the water outlet, so that the brine and distilled water do not mix. The filter paper sucks the brine to the lower surface of the tungsten carbide nanoarray (the tungsten carbide nano webbed array material obtained in Example 4) by capillary force, and the brine enters the tungsten carbide nanoarray. Under light conditions, the tungsten carbide nanoarray will produce a relatively high temperature, the brine evaporates on the surface of the tungsten carbide nanoarray, the steam condenses on the "condensation cover", and the condensed distilled water flows into the "distilled water collection tank" and is stored in the lower part of the "distilled water collection tank" with a relatively low temperature.

The water quality before and after treatment of artificially synthesized seawater and artificially synthesized heavy metal ion sewage is shown in Figure 14. It can be seen from Figure 14 that before treatment, the contents of sodium ions, magnesium ions, potassium ions, and calcium ions in the artificially synthesized seawater were 10000ppm, 1000ppm, 120ppm, and 130ppm respectively. After treatment, the sodium ions, magnesium ions, and The concentrations of potassium ions and calcium ions were 0.6ppm, 0.2ppm, 0.05ppm, and 0.1ppm, respectively, all of which fell below 1ppm. The contents of heavy metal arsenic, cadmium and lead in heavy metal polluted sewage before treatment are 1000ppb, 2000ppb and 1700ppb respectively, which are about 100 times, 400 times and 110 times that of the first-class drinking water standard in the United States. After treatment, arsenic, cadmium, The concentration of lead has been reduced to below the first-class drinking water standard in the United States, which are 0.01ppb, 0.17ppb and 0.5ppb respectively, which fully meets the drinking water standard requirements.

Claims (10)

1. a kind of tungsten carbide nano-array material, which is characterized in that including base material and the carbonization being grown on base material Tungsten nano array structure material.

2. tungsten carbide nano-array material according to claim 1, which is characterized in that the tungsten carbide nano array structure Material is N doping or non-N doping.

3. tungsten carbide nano-array material according to claim 1 or 2, which is characterized in that the base material for metal, One or more of quartz glass, silicon, ceramics or carbon material.

4. tungsten carbide nano-array material according to claim 1 or 2, which is characterized in that the tungsten carbide nano-array Structural material only has characteristic peak, the characteristic peak of carbon and the characteristic peak of tungsten carbide of substrate in XRD spectrum.

5. tungsten carbide nano-array material according to claim 1 or 2, which is characterized in that the tungsten carbide nano-array Including nano-wire array, nano-band array, nanometer columnar arrays or nanometer web shape array.

6. a kind of preparation method of tungsten carbide nano-array material, which is characterized in that include the following steps：

(1) base material is added after adding in pH adjusting agent and pattern conditioning agent in tungstenic solution, at 120 DEG C~200 DEG C 0.5~20h of hydro-thermal reaction in closed container, cooling obtain tungsten oxide nanometer array material.

(2) the tungsten oxide nanometer array material for obtaining step (1) is together with carbon source, in 800 DEG C~950 DEG C and indifferent gas condition It is lower that 0.5~3h is kept to obtain the tungsten carbide nano-array material.

7. preparation method according to claim 6, which is characterized in that tungstenic solution described in step (1) is tungstic acid, One or more of ammonium tungstate solution, sodium tungstate solution, tungsten chloride solution；The base material for metal, quartz glass, One or more of silicon, ceramics or carbon material.

8. preparation method according to claim 6, which is characterized in that pH adjusting agent described in step (1) is acid, alkali, salt, One or more of oxide；The pattern conditioning agent is sodium sulphate, potassium sulfate, sodium chloride, potassium chloride, ammonium sulfate or chlorination One or more of ammonium.

9. preparation method according to claim 6, which is characterized in that the carbon source described in step (2) is melamine, double cyanogen One or more of amine, terpene, the terpene are one or more of camphor, laurene, citral.

10. tungsten carbide nano-array material according to claim 1 or 2 for water photo-thermal evaporation or in acid condition The purposes of electrocatalytic hydrogen evolution or electro-catalysis analysis oxygen.