阅读说明：本技术 一种z型异质结构氮化钨-三氧化钨复合材料及制备方法和应用 (Z-type heterostructure tungsten nitride-tungsten trioxide composite material and preparation method and application thereof ) 是由 张兵 孙孟尧 刘大李 赵博航 于 2019-02-27 设计创作，主要内容包括：本发明公开一种Z型异质结构氮化钨-三氧化钨复合材料及制备方法和应用。本发明的复合材料包括表面部分氧化的三氧化钨层和内部氮化钨纳米棒。本发明通过原位转化的方法设计合成了氮化钨-三氧化钨复合材料,在氮化钨表面将其部分氧化为三氧化钨以达到构建Z型异质结构的目的。本发明提出了一种简便且普适的制备方法,使氮化钨能够破除自身光生电子和空穴易于复合的限制,对太阳光中紫外-可见光部分实现了更好的利用。(The invention discloses a Z-type heterostructure tungsten nitride-tungsten trioxide composite material, a preparation method and application thereof. The composite material comprises a tungsten trioxide layer with partially oxidized surface and tungsten nitride nanorods inside. The tungsten nitride-tungsten trioxide composite material is designed and synthesized by an in-situ conversion method, and is partially oxidized into tungsten trioxide on the surface of tungsten nitride so as to achieve the purpose of constructing a Z-shaped heterostructure. The invention provides a simple and universal preparation method, which can remove the limit that self photoproduction electrons and holes are easy to combine and better utilize ultraviolet-visible light in sunlight.)

1. A Z-type heterostructure tungsten nitride-tungsten trioxide composite material is characterized by comprising a tungsten trioxide layer obtained by partial oxidation of the surface and tungsten nitride nanorods inside, wherein a Z-type heterostructure is formed between the tungsten trioxide layer on the surface and the tungsten nitride nanorods inside, and the Z-type heterostructure is formed according to the following steps: placing the tungsten nitride nanorod in an air atmosphere, heating to 300-350 ℃ at a heating rate of 1-5 ℃ per minute, carrying out heat preservation reaction for 1-2 hours, and naturally cooling to room temperature to obtain a tungsten nitride nanorod with a partially oxidized surface, namely the tungsten nitride-tungsten trioxide composite material with a Z-shaped heterostructure, which is composed of a tungsten trioxide layer obtained by partially oxidizing the surface and the tungsten nitride nanorod inside.

2. The Z-type heterostructure tungsten nitride-tungsten trioxide composite material as claimed in claim 1, wherein the composite material has a length of 1-5 μm and a width of 100-150 nm; preferably 1-3 microns in length and 100-120 nm in width.

3. The Z-type heterostructure tungsten nitride-tungsten trioxide composite material of claim 1, wherein the incubation reaction is carried out at 300-320 ℃ for 1-1.5 hours.

4. A preparation method of a Z-type heterostructure tungsten nitride-tungsten trioxide composite material is characterized in that a tungsten nitride nanorod is placed in an air atmosphere, heated to 300-350 ℃ at a heating rate of 1-5 ℃ per minute, subjected to heat preservation reaction for 1-2 hours, and naturally cooled to room temperature (20-25 ℃) to obtain a tungsten nitride nanorod with a partially oxidized surface, namely the Z-type heterostructure tungsten nitride-tungsten trioxide composite material consisting of a tungsten trioxide layer obtained by partially oxidizing the surface and the tungsten nitride nanorod inside.

5. The preparation method of the Z-type heterostructure tungsten nitride-tungsten trioxide composite material as claimed in claim 4, wherein the reaction is carried out at 300-320 ℃ for 1-1.5 hours; a quartz tube is selected as reaction equipment, and air is introduced to serve as reaction atmosphere.

6. The method for preparing the Z-shaped heterostructure tungsten nitride-tungsten trioxide composite material as claimed in claim 4, wherein the tungsten nitride nanorod is prepared by performing hydrothermal reaction on tungsten trioxide and ethylenediamine to obtain a tungsten trioxide-ethylenediamine precursor, calcining at a high temperature to obtain the tungsten trioxide nanorod, and finally performing high-temperature reaction in an ammonia atmosphere to obtain the tungsten nitride nanorod, which is specifically as follows:

step 1, weighing tungsten trioxide, adding ethylenediamine, and uniformly stirring, wherein the ratio of the mass (g) of the added tungsten trioxide to the volume (mL) of the ethylenediamine is 1: (28-35), stirring for 0.5-1 h;

step 2, transferring the mixed solution obtained in the step 1 to a stainless steel autoclave with a polytetrafluoroethylene lining for reaction at the temperature of 150 ℃ and 200 ℃ for 6-12h, and centrifugally collecting to obtain a white tungsten trioxide-ethylenediamine precursor;

step 3, placing the white tungsten trioxide-ethylenediamine precursor prepared in the step 2 in a quartz tube with the diameter of 6mm, calcining at the high temperature of 700-750 ℃ for 10-15h at the heating rate of 1-5 ℃/min to obtain a tungsten trioxide nanorod;

and 4, continuously placing the tungsten trioxide nano rod prepared in the step 3 in a quartz tube with the diameter of 6mm, reacting for 2-5h at the temperature of 700-.

7. The method for preparing a Z-type heterostructure tungsten nitride-tungsten trioxide composite material according to claim 6, wherein, in preparing the tungsten nitride nanorod, the ratio of the mass (g) of tungsten trioxide to the volume (mL) of ethylenediamine in step 1 is 1: (30-32); in the step 2, the reaction temperature is 160-180 ℃, and the reaction time is 8-10 hours; in the step 3, selecting an air atmosphere, wherein the high-temperature calcination temperature is 700-720 ℃, and the time is 3-5 hours; in step 4, selecting ammonia atmosphere, and reacting at 720-750 deg.C for 3-5 hr.

8. Use of a Z-type heterostructure tungsten nitride-tungsten trioxide composite material according to any of claims 1 to 3 for photo-thermal catalytic carbon dioxide hydrogenation.

9. The use according to claim 8, wherein, in the use, the Z-type heterostructure tungsten nitride-tungsten trioxide composite material is dispersed in a solution of potassium chloropalladite to form a suspension, the suspension is sufficiently stirred and illuminated under an inert protective gas atmosphere, the precipitate is separated by centrifugation,then washing the composite material for multiple times by using deionized water and ethanol, drying the composite material in a vacuum drying oven to obtain a palladium-loaded tungsten nitride-tungsten trioxide nanorod, weighing 25-50mg of the palladium-loaded Z-type heterostructure tungsten nitride-tungsten trioxide composite material, dispersing the weighed composite material in a reaction tank in a photo-thermal reactor to perform photo-thermal catalytic carbon dioxide hydrogenation, wherein the methane generation rate can reach 40.6-42.3 mu mol h^-1g^-1。

10. Use according to claim 9, wherein the solution of potassium chloropalladite has a molar concentration of 0.14 to 0.15 μmol/L, the solvent is water and methanol, and the percentage by volume of methanol is 6 to 8%. The mass ratio of the Z-type heterostructure tungsten nitride-tungsten trioxide composite material to potassium chloropalladite is 300: (6-10), preferably 300: (7-9); the inert protective gas is argon, nitrogen or helium; the stirring speed is 100-500 revolutions per minute, preferably 300-500 revolutions per minute; the illumination is selected to be fluorescent lamp or xenon lamp to simulate sunlight, and the simulated light intensity is 0.4-0.5W/cm^-2(ii) a The stirring and the light irradiation are carried out for a time period (time period in which both are carried out simultaneously) of 1 to 2 hours, preferably 1 to 1.5 hours.

Technical Field

The invention relates to the technical field of semiconductor nano materials, in particular to a Z-type heterostructure tungsten nitride-tungsten trioxide composite material, a preparation method and application thereof.

Background

In recent years, with the explosion of energy crisis, the development of new energy is an urgent problem to be solved in the society today. The conversion of carbon dioxide into hydrocarbon fuel driven by sunlight has very important research significance and application value for relieving the problems of energy shortage and environmental pollution faced by the current society. Due to high photo-thermal conversion efficiency, the photo-thermal method becomes an effective way for carbon dioxide hydrogenation. However, the ultraviolet-visible light part of sunlight in the traditional light-heat conversion is not fully utilized, so that not only are the reaction conditions severe, but also a sacrificial agent needs to be introduced. Tungsten nitride (WN) is an inorganic material with a wide prospect in photo-thermal catalysis due to good solar energy absorption and electron transmission performance. However, it is very limited in its application because of the low activity of bulk tungsten nitride in general and the difficulty in efficiently separating and transferring photogenerated electrons and holes. Therefore, it remains a great challenge to develop an effective method to improve the activity of tungsten nitride photocatalyst. The performance and stability of the semiconductor photocatalyst can be effectively improved by constructing a heterostructure. For heterogeneous catalysts, charge separation and surface reactions are critical factors in achieving photoconversion efficiency. Therefore, constructing a semiconductor-based Z-type heterostructure is also a powerful strategy to improve the efficiency of the photothermal catalytic reaction.

Disclosure of Invention

Aiming at overcoming the technical defects in the prior art, the invention provides a Z-type heterostructure tungsten nitride-tungsten trioxide composite material, a preparation method and application thereof, wherein tungsten nitride-tungsten trioxide (WN-WO) is designed and synthesized by an in-situ conversion method₃) The composite material is prepared by partially oxidizing tungsten nitride on the surface of tungsten nitride into tungsten trioxide so as to achieve the purpose of constructing a Z-shaped heterostructure. A tungsten trioxide precursor is prepared by a simple hydrothermal technology, and the tungsten nitride-tungsten trioxide composite material with high stability and high photo-thermal catalytic carbon dioxide hydrogenation activity is prepared through a series of processes such as high-temperature calcination, complete nitridation, partial oxidation and the like.

The technical purpose of the invention is realized by the following technical scheme.

A Z-type heterostructure tungsten nitride-tungsten trioxide composite material is composed of a tungsten trioxide layer obtained by partial oxidation of the surface and tungsten nitride nanorods inside, and a Z-type heterostructure is formed between the tungsten trioxide on the surface and the tungsten nitride inside.

Moreover, the length of the composite material is 1-5 microns, and the width is 100-150 nanometers; preferably 1-3 microns in length and 100-120 nm in width.

A preparation method of a Z-type heterostructure tungsten nitride-tungsten trioxide composite material comprises the steps of placing tungsten nitride nanorods in an air atmosphere, heating to 300-350 ℃ at a heating rate of 1-5 ℃ per minute, carrying out heat preservation reaction for 1-2 hours, and naturally cooling to room temperature (20-25 ℃) to obtain partially oxidized tungsten nitride nanorods, namely the Z-type heterostructure tungsten nitride-tungsten trioxide composite material consisting of a tungsten trioxide layer obtained by surface partial oxidation and the tungsten nitride nanorods inside.

Moreover, the reaction is carried out for 1 to 1.5 hours at 300 to 320 ℃.

Moreover, a quartz tube is selected as a reaction device, and air is introduced to serve as a reaction atmosphere.

The tungsten nitride nanorod is prepared by adopting the prior art (Yu Lei Wang, Ting Nie, Yu Handg Li, Xue LuWang, Li Rong, Zheng, Ai Ping Chen, Xue Qing Gong, and Huagui Yang, Black tung nitride as Metallic photo catalyst for aqueous coating up 765nm, http:// dx.doi.org/10.1002/anie.201702943, http:// dx.doi.org/10.1002/ange.201702943), tungsten trioxide and ethylenediamine are subjected to hydrothermal reaction to obtain a tungsten trioxide-ethylenediamine precursor, the tungsten nitride nanorod is obtained after high-temperature calcination, and finally, the tungsten nitride nanorod is obtained by high-temperature reaction in an ammonia atmosphere. The method comprises the following specific steps:

step 1, weighing tungsten trioxide, adding ethylenediamine, and uniformly stirring, wherein the ratio of the mass (g) of the added tungsten trioxide to the volume (mL) of the ethylenediamine is 1: (28-35), stirring for 0.5-1 h;

step 2, transferring the mixed solution obtained in the step 1 to a stainless steel autoclave with a polytetrafluoroethylene lining for reaction at the temperature of 150 ℃ and 200 ℃ for 6-12h, and centrifugally collecting to obtain a white tungsten trioxide-ethylenediamine precursor;

step 3, placing the white tungsten trioxide-ethylenediamine precursor prepared in the step 2 in a quartz tube with the diameter of 6mm, calcining at the high temperature of 700-750 ℃ for 10-15h at the heating rate of 1-5 ℃/min to obtain a tungsten trioxide nanorod;

and 4, continuously placing the tungsten trioxide nano rod prepared in the step 3 in a quartz tube with the diameter of 6mm, reacting for 2-5h at the temperature of 700-.

In step 1, the ratio of the mass (g) of tungsten trioxide to the volume (mL) of ethylenediamine is 1: (30-32).

In the step 2, the reaction temperature is 160-180 ℃, and the reaction time is 8-10 hours.

In step 3, selecting air atmosphere, and calcining at 700-720 ℃ for 3-5 hours at high temperature.

In step 4, selecting ammonia atmosphere, and reacting at 720-750 deg.C for 3-5 hr.

The invention relates to an application of a Z-type heterostructure tungsten nitride-tungsten trioxide composite material in photo-thermal catalytic carbon dioxide hydrogenation.

When the preparation method is used, the Z-type heterostructure tungsten nitride-tungsten trioxide composite material (namely tungsten nitride-tungsten trioxide black powder) is dispersed in a solution of potassium chloropalladite to form a suspension, the suspension is fully stirred and illuminated under the inert protective gas atmosphere, the precipitate is centrifugally separated, and then is washed for multiple times by deionized water and ethanol, and is dried in a vacuum drying oven to obtain the palladium-loaded tungsten nitride-tungsten trioxide nanorod.

In the solution of potassium chloropalladite, the molar concentration of the potassium chloropalladite is 0.14-0.15 mu mol/L, the solvent is water and methanol, and the volume percentage of the methanol is 6-8%. The mass ratio of the Z-type heterostructure tungsten nitride-tungsten trioxide composite material to potassium chloropalladite is 300: (6-10), preferably 300: (7-9).

The inert protective gas is argon, nitrogen or helium; the stirring speed is 100-500 revolutions per minute, preferably 300-500 revolutions per minute; the illumination is selected to be fluorescent lamp or xenon lamp to simulate sunlight, and the simulated light intensity is 0.4-0.5W/cm^-2(ii) a Stirring and illuminatingThe time (the time during which both are carried out simultaneously) is from 1 to 2 hours, preferably from 1 to 1.5 hours.

Weighing 25-50mg of the Z-shaped heterostructure tungsten nitride-tungsten trioxide composite material loaded with palladium, dispersing the weighed material in a reaction tank in a photo-thermal reactor for photo-thermal catalytic carbon dioxide hydrogenation, wherein the methane generation rate can reach 40.6-42.3 mu mol h^-1g^-1. The photo-thermal catalytic carbon dioxide hydrogenation reaction is carried out in a stainless steel reaction chamber lined with polytetrafluoroethylene, and the top of the reaction chamber is provided with a quartz window for light irradiation. The reaction chamber volume is 75mL, the sample in the reaction chamber dispersion. The chamber is evacuated of gas by a mechanical pump prior to photoreaction. Then carbon dioxide bubbled with water is added into the reaction chamber, and the pressure reaches 0.10-0.12 MPa. The 300W xenon lamp with the AM 1.5G filter is adopted to simulate the sunlight, and the simulated light intensity is 0.4W/cm^-2Samples were taken from the chamber at regular intervals for measurement. The product was analyzed by gas chromatography (helium as carrier gas, BID detector).

The palladium-loaded tungsten nitride-tungsten trioxide nanorod disclosed by the invention is applied to photo-thermal catalytic carbon dioxide hydrogenation.

Compared with the prior art, the invention has the following beneficial effects: (1) the invention provides a simple and universal preparation method for in-situ construction of a Z-type heterostructure tungsten nitride-tungsten trioxide composite material on the surface of tungsten nitride, which fills the blank of the field, enables the tungsten nitride to break the restriction that self photoproduction electrons and holes are easy to compound, and realizes better utilization of ultraviolet-visible light in sunlight; (2) the Z-type heterostructure tungsten nitride-tungsten trioxide composite material has the advantages of low cost, simple synthesis process, high photo-thermal conversion efficiency, strong light absorption capacity and the like; (3) the Z-type heterostructure tungsten nitride-tungsten trioxide composite material is easy to excite and generate photoproduction electrons, keeps the separation efficiency of electrons and holes and the transmission capability of electrons, and has remarkable advantages in the aspect of photo-thermal catalytic carbon dioxide hydrogenation.

Drawings

FIG. 1 is a Z-type heterostructure WN-WO prepared by the present invention₃Nanorod Scanning Electron Microscope (SEM) photographs.

FIG. 2 is a Z-type heterostructure WN-WO prepared by the present invention₃Nanorod Transmission Electron Microscope (TEM) photographs.

FIG. 3 is a Z-type heterostructure WN-WO prepared by the present invention₃High Resolution Transmission Electron Microscopy (HRTEM) photographs of nanorods.

FIG. 4 is a Z-type heterostructure WN-WO prepared by the present invention₃X-ray diffraction (XRD) pattern of nanorods.

FIG. 5 is a Z-type heterostructure WN-WO prepared by the present invention₃Comparison graph of photo-thermal catalysis carbon dioxide hydrogenation performance of nano-rod, wherein WN-WO₃Is a Z-type heterostructure WN-WO prepared by the invention₃A nanorod; WO₃As WO₃Nanorods, WN being WN nanorods, both prepared by the prior art procedure indicated in the present invention, WO₃The nano-rod is obtained through the step 1-3, and the WN nano-rod is obtained through the step 1-4.

FIG. 6 is a schematic diagram of a Z-type heterostructure WN-WO prepared by the present invention₃Method for testing raw materials by using nanorod photo-thermal catalysis carbon dioxide hydrogenation¹³C isotope tracing analysis chart.

FIG. 7 is a schematic diagram of a Z-type heterostructure WN-WO prepared by the present invention₃Nanorod in-situ illumination XPS analysis chart.

Detailed Description

The invention is described in further detail below with reference to the figures and specific examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The chemical reagents used in the invention are analytically pure tungsten trioxide, ethylenediamine, potassium chloropalladite, ethanol and methanol. The hydrothermal reaction kettle in step 2 is generally a stainless steel reaction kettle with polytetrafluoroethylene as a lining.