With the development of modern industry, the situation of air pollution, water pollution and soil pollution is getting worse and worse. People feel the harm of environmental pollution to themselves. Protecting the environment is to save themselves. People urgently need a low cost, high efficiency and energy for non-toxic degradation and purification.

Although sunlight is a clean energy source, many problems hinder its widespread use. The most important is its intermittence, which is not always sunny, and sunny periods are not always highly correlated with electricity demand. In addition, if the electricity generated by solar energy cannot be used or stored immediately, it will be wasted. Therefore, there is a need for a practical way to store solar energy, which can be used when needed. These means can make people use solar energy and hydrogen energy more efficiently and further reduce their dependence on oil.

Titanium dioxide is known as a photocatalyst material, but it has little function in the absence of ultraviolet radiation. Therefore, Scientists prefer to study visible-light tungsten trioxide photocatalysts.

Energy shortage and environmental deterioration have become the most important problems facing all countries in the world. The development of new functional materials will be an effective way to solve these problems. Because of its unique physical and chemical and electronic properties, tungsten oxide materials have good application prospects in the fields of color-changing window, photocatalysis, fuel cell, chemical sensor, environmental purification, solar energy conversion and other functions, and have become one of the hot topics in the current research of new materials.

At present, most power plants in our country mainly use coal as fuel. The direct combustion of coal will produce a large number of nitrogen oxides which pollute the environment. At present, flue gas denitrification technology is widely used in developed countries to reduce the emission of nitrogen oxides, and the denitrification rate can reach more than 90%.

Recently, some scholars have attempted to prepare tungsten trioxide nanosheets with high specific surface area, high crystallinity, high dispersibility and low cost by mechanochemical method. The main process is to prepare tungstic acid (WO₃·H₂O) nanosheets using tungstic acid-based organic or inorganic layered hybrid micro/nanobelts (tubes) as precursors, and remove the organic matter between the precursor layers by nitric acid oxidation. The reaction temperature is 15-50 ℃. The time is 5-120 H. The tungsten oxide nanosheets are prepared by heating them at a heating rate of 1-5 ℃/min to 250-600 ℃, then holding them for 1-5 h, and then cooling them to room temperature naturally. The specific operation is as follows:

Carbon nanotubes (CNTs) have a special structure consisting of hexagonal networks similar to graphite. Unique nano-hollow structure and closed spiral structure of different topological levels make it have a lot of special excellent properties, such as good electrical conductivity, heat resistance, high mechanical strength, corrosion resistance, self-lubrication and biocompatibility. These excellent properties make carbon nanotubes have great application prospects in composite materials, hydrogen storage materials and catalyst materials.

Tungsten is an important strategic metal resource. Ammonium paratungstate/tungsten trioxide is an important chemical product of tungsten. Qualified products of ammonium paratungstate and tungsten oxide are produced in tungsten smelting process, or waste materials of ammonium paratungstate and tungsten oxide are collected.

In the research of traditional catalysts, titanium dioxide (titanium dioxide) is widely used to treat various environmental pollution problems by its photocatalytic reaction. However, titanium dioxide can only be stimulated by ultraviolet light, and ultraviolet light only accounts for about 5% of the energy in sunlight. Therefore, there is a problem of insufficient utilization of solar energy. Therefore, researchers are looking for other new photocatalysts, including trioxide. Tungsten oxide (WO₃), however, can absorb UV light with wavelength less than 460nm. The utilization of other visible and infrared energy is still low.

There are many materials that can be used as photocatalyst in the world, including titanium dioxide (titanium dioxide), zinc oxide (zinc oxide), tin oxide (SnO₂), zirconium dioxide (ZrO₂), tungsten trioxide (WO₃) and other oxide sulfide semiconductors. Among them, titanium dioxide is the most common Nano-Photocatalyst material in the world because of its strong oxidation ability, stable chemical properties and non-toxic.