Modification of TaON with ZrO2 to improve photocatalytic hydrogen evolution activity under visible light: influence of preparation conditions on activity

The effects of the preparation conditions of ZrO2-modified TaON (referred to as ZrO2/TaON) on the photocatalytic activity for H2 evolution under visible light (λ > 420 nm) were investigated. ZrO2/TaON catalysts were prepared by loading particulate Ta2O5 with ZrO2 using different zirconium precursors, followed by nitridation at 1123 K for different durations (5–20 h) under NH3 flow. Nitridation of ZrO2/Ta2O5 for 15 h resulted in the production of ZrO2/TaON, regardless of the zirconium precursors used, but the physicochemical properties varied. The highest activity was obtained for ZrO2/TaON synthesized from Ta2O5 and ZrO(NO3)2·2H2O (Zr/Ta = 0.1 by mole) after nitridation for 15 h. Physicochemical analysis suggested that a lower density of anionic defects in TaON, which was realized using highly-dispersed ZrO2 nanoparticles (10–30 nm in size), contributed primarily to the enhanced activity.