Supercapacitors are energy storage devices between batteries and traditional capacitors. Because of its high charging and discharging efficiency, high power density, long cycle life and friendly environment, it is widely used in transportation, mobile communications, information technology, aviation, aerospace and national defense science and technology.

Since the first discovery of photocatalysis by Japanese scientists in 1972, photocatalysis has been applied in many fields, including water treatment, and its development prospects have been widely recognized. Tungsten trioxide is regarded as one of the most promising photocatalysts because of its visible light response. However, one of the difficult problems it faces is its poor catalytic activity. Therefore, it is still the focus of photocatalytic research to find a simple synthesis method, low cost and high photocatalytic activity of tungsten trioxide.

At present, the main friction materials are carbon fibers and carbon composites. Because the wear resistance of carbon composites is relatively low and easy to wet, people are looking for friction materials with higher wear resistance.

Photocatalysis is a technology that uses the light energy existing in nature to convert into the energy needed for chemical reaction to produce catalytic effect. By this way, it can decompose organic substances harmful to human body and environment without causing waste of resources and formation of additional pollution. A large number of studies have shown that almost all organic pollutants can be effectively photocatalytically degraded.