Photoelectrochemical properties of TiO2 photocatalyst and its applications for environmental purification

In view of the situation that environmental issues become more serious day by day, recent studies on practical applications of TiO2 photocatalysis for environmental purification are reviewed. Although the fundamental aspects and the mechanisms of TiO2 photocatalysis have recently become quite well understood, effective photocatalytic environmental purifier, especially water purifier, could not be developed to the stage of real industrial technology. The removal rate of gaseous or aqueous contaminants is influenced by numerous parameters; UV light intensity, substrate concentration, O2 partial pressure, humidity, substrate type, and so on. Moreover, TiO2 photocatalyst essentially has a difficulty in decomposition of large amount of contaminants or refractory chemicals. As the solutions of these problems, combination with other processes such as advanced oxidation processes and improvement of the design of photocatalytic environmental purification systems are described. During the past several years, the strategies for effective design of the system are well discussed and evaluated. The reactor design for air- or water-purification can be classified into two main strategies: (1) enlargement of reactive surface area and (2) improvement of mass transfer. Based on these insights, very recent achievements for development of photocatalytic environmental purification system with our contribution in each aspect and future research directions are reviewed.

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► Recent studies on practical applications of TiO2 photocatalysis for environmental purification.
► Synergistic effects by combination with other processes such as advanced oxidation processes.
► Theoretical strategies for the effective design of the environmental purification systems.