Development of TiO₂ photocatalysts suitable for practical use and their applications in environmental cleanup

Abstract

Recently, environmental disruption is proceeding on a global scale through the consumption of huge amounts of fossil fuels and the emission of various chemical substances. However, these substances resist bio-treatment. TiO₂ generates electrons and holes by irradiation with light. Most organic micro-pollutants, including dioxins, are decomposed into carbon dioxide and water by the effect of the holes with high oxidative potential. By using such a photocatalytic reaction, various applications are feasible for environmental cleanup. In general, TiO₂ powder has been utilized as photocatalyst, although TiO₂ powder photocatalyst has several disadvantages: (1) it is difficult to handle, (2) photocatalytic reaction is slow and it takes a lot of time for treatment and (3) it is difficult to apply to plastics and textiles, because the photocatalyst decomposes them. We have developed a photocatalyst suitable for practical use and have developed high-activity photocatalysts such as TiO₂ photocatalytic transparent film, photocatalytic silica-gel, apatite-coated TiO₂ photocatalyst usable for plastics and textiles, photocatalytic paper, photocatalytic blue charcoal and photocatalytic oxygen scavenger. The application of these high-activity photocatalysts has been studied in deodorization, anti-bacterial, self-cleaning, anti-stain, water treatment, air purification such as photocatalytic decomposition of dioxins and VOC, and NO _x removal. Now various photocatalytic articles using these new photocatalyst materials are on the market in Japan. Photocatalytic technology can create many valuable products for environmental use all over the world.