16
113photocatalytic development photocatalyst was discovered in 1967 by professor hiroshi fujishima, then a graduate student of tokyo university. in one experiment, the single crystal of titanium oxide in water was irradiated by light. it was found that water was decomposed into oxygen and hydrogen. the effect is known as the "honda fujishima effect," which combines the name of professor fujishima and then his instructor, kenichi honda, president of tokyo university of technology. titanium oxide in this phenomenon was later called photocatalyst because it promoted the oxidative decomposition reaction with the help of light. this phenomenon is equivalent to turning light energy into chemical energy. at that time, under the background of the oil crisis, the world was eager to find new energy. therefore, this technology, as a landmark method of extracting hydrogen from water, attracted great attention. however, it is difficult to extract large amount of hydrogen in a short time, so the development of new energy could not be realized after all, so it became a sensation after that, the temperature dropped rapidly.
in 1992, the first international symposium on titanium dioxide photocatalyst was held in canada. japanese research institutions published many new ideas about photocatalyst and put forward research results applied to nitrogen oxide purification. therefore, the number of patents related to titanium dioxide is also the largest, and other catalyst related technologies include catalyst deployment process, catalyst structure, catalyst support, catalyst fixation method, catalyst performance test, etc. taking this opportunity, the research on photocatalyst used in antibacterial, antifouling, air purification and other fields has increased dramatically. from 1971 to june 2000, a total of 10717 patents related to photocatalyst have been filed. the wide application of tio2 photocatalyst will bring people clean environment and healthy body. the length of an object is 10-6 meters, which is called micrometer (mm), and 10-9 meters, which is called nanometer (nm). all kinds of application materials will gradually enter the nano era from micron. nanomaterials are composed of particles with grain size of 1-100nm. with the decrease of particle size, the percentage of surface atoms increases. the phenomenon of high surface energy is caused by the incomplete coordination of a large number of atoms on the surface. the ratio of surface energy to total energy is greatly increased, which makes nanomaterials have the characteristics of adsorption, light absorption and melting point change. by using the technology and characteristics of nano ultrafine particles, the material itself is developed which does not participate in the reaction at all, but can promote and improve the reaction energy. the catalyst technology which catalyzes the target reaction has been used in the role of environmental cleaning, which can accelerate the reaction of harmful or toxic substances to become stable and harmless substances and achieve the environmental protection effect. nano titanium dioxide photocatalyst is a kind of substance which can promote chemical reaction, just like chlorophyll in photosynthesis of plants. tio2 photocatalyst can produce antibacterial, deodorizing, oil decomposition, mildew and algae prevention and air purification effects under the sunlight or indoor fluorescent lamp.
