Nanoparticulate precursor route to fine particles of TaON and ZrO2–TaON solid solution and their photocatalytic activity for hydrogen evolution under visible light Original Research Article

Preparation of fine TaON particles is attempted to improve the photocatalytic activity for H2 evolution from aqueous methanol solution under visible light (λ > 420 nm). TaON is synthesized by nitriding Ta2O5 powder at 1123 K for 15 h under a flow of NH3. When nanoparticulate Ta2O5 with a primary particle size of 30–50 nm is used as the precursor, fine particles of TaON (FP-TaON) with 50–80 nm in size is obtained, but the primary particles aggregate to form larger secondary particles. Nitridation of Zr–Ta mixed oxide (Zr/Ta = 0.1) nanoparticles results in the production of a solid solution of monoclinic-ZrO2 and TaON exhibiting 30–50 nm primary particle size with less aggregation and higher activity, as compared to FP-TaON. Suppression of surface defects (reduced tantalum species) produced during nitridation from Ta2O5 to TaON is shown to be essential for achieving efficient H2 evolution using TaON-based photocatalysts.