At present, due to the increasingly high energy shortage and environmental pollution caused by the rapid development of industry, the demand for clean energy and clean technology that can effectively use solar energy is becoming more and more urgent. The photocatalytic technology is environmentally friendly, energy-saving, mild in response conditions and The advantages of secondary pollution show good application prospects. Among many photocatalytic materials, Bi2WO6 is a kind of visible light photocatalyst with many researches and good photocatalytic activity.

With the development of science and technology, toxic organic pollutants from industrial and agricultural production seriously threaten the environment and human health. It is of great significance to seek a new and efficient environmental treatment technology. Photocatalytic technology has become a new environmental treatment technology with important application prospect because of its advantages of energy saving, high efficiency, complete pollutant degradation and no secondary pollution.

Heteropolyacids have been developed for more than 100 years, and the research contents have been gradually extended to material chemistry, electrochemistry, catalytic chemistry, photochemistry, surface science, medicine and other fields. Therefore, heteropolyacids show high catalytic activity and selectivity for various organic reactions.

Tungsten oxide (WO₃) thin film is an ideal electrochromic and energy storage material due to its high contrast, good stability of crystal structure, strong environmental affinity and low cost. It is found that the smart window dual-function device based on the tungsten oxide film of indium ferrocyanide includes two conductive substrates as the working electrode and the reference electrode, one of which is coated with the tungsten oxide film on the surface of the conductive substrate to form the reference electrode structure, the other is coated with the indium ferrocyanide film on the surface of the conductive substrate to form the working electrode structure. The preparation steps of the film are as follows:

Electrochromism refers to the phenomenon that the optical properties of materials change reversibly under the action of external electric field. Electrochromism only needs a small voltage (about 2V) to work. In the open circuit state, it can keep the original color or fading state unchanged, so it consumes less energy.

Tungsten trioxide electrode and its preparation method, and its application in photo catalytic decomposition of water use semiconductor photo catalytic technology to convert solar energy into hydrogen energy through water decomposition, and store and use hydrogen in the form of chemical energy, is one of the most promising ways to solve the current energy crisis.

Generally, violet tungsten oxide is obtained by calcining ammonium paratungstate in a rotary furnace. The prepared violet tungsten oxide is ultrafine and of good quality. During the preparation process, furnace temperature, furnace tube speed and feeding speed are the three factors that affect the properties of violet tungsten oxide.

Violet tungsten oxide is powder with unique structure of needle. It is composed of many different components. The components and their quantities are determined by the specific preparation method. Violet tungsten oxide has some alternate names -γ-tungsten oxide, for example.

Violet tungsten oxide with low apparent density has high application value in the field of powder metallurgy. It is an extremely important material for the preparation of ultrafine tungsten powder and tungsten carbide. Low apparent density of violet tungsten oxide is determined by its unique needle structure.

PEC technology is based on solar energy and water, both of which are renewable. PEC technology has no by-products and will not bring pollution to the environment. Moreover, PEC technology can be applied in small scale and developed in large scale. Therefore, this technology is the most attractive way to produce hydrogen directly by solar energy.