Synergy of sodium and WO3 for the formation of anatase-based TiO2 nanoporous films with enhanced photoactivity

This study examines the structural evolution and photoactivity of sputter-deposited TiO2-WO3 films upon annealing in terms of the role played by sodium contained in glass substrates. Even though it is generally agreed that sodium contaminates TiO2 photocatalysts, we discover that the sodium content of the glass is a key factor in drawing out the incorporated WO3 and retarding TiO2 grain growth, ultimately forming a nanoporous film with an anatase matrix. It is found that an alkylsiloxane monolayer on this film decomposes much faster than the layer on a film that is free of sodium uptake. The enhancement of the film′s photocatalytic activity is elucidated by structural analysis.