Evaluation of photocatalytic activities and characteristics of Cu- or Fe-modified nitrogen-doped titanium dioxides for applications in environmental purification

Photocatalytic activities, as manifested in gas decomposition rates of volatile organic compounds under visible light irradiation, are well known to be enhanced by Cu or Fe compounds loaded onto the surface of nitrogen-doped titanium dioxide (N-TiO2). Antimicrobial properties are also known to be improved by Cu compounds loaded onto N-TiO2. In this study, the acetaldehyde gas decomposition rates and antimicrobial properties achieved by loading Cu or Fe compounds onto N-TiO2 have been investigated from a practical viewpoint. Enhancements of the photocatalytic activities have been confirmed, and the durability of the Cu- or Fe-modified N-TiO2 in acetaldehyde gas decomposition has been demonstrated. The enhancements have been rationalized by considering the valence states of the loaded material. The enhancements were inferred to be a result of increased amounts of oxidative species arising from the photo-Fenton reaction at the surface of the loaded metal compounds. With a view to expanding the range of indoor applications of such visible-light-sensitive photocatalysts, preparation processes, i.e., nanosizing of the powder and improvement of the immobilization on various substrates, are also discussed. (C) 2016 The Japan Society of Applied Physics