Surface modification of TaON with monoclinic ZrO2 to produce a composite photocatalyst with enhanced hydrogen evolution activity under visible light

A composite material consisting of tantalum oxynitride (TaON) and monoclinic zirconium oxide (m-ZrO2) is prepared by a surface modification method as a photocatalyst with enhanced activity for H-2 evolution from water under visible light (lambda > 420 nm). The composite is prepared by loading particulate Ta2O5 with nanoparticulate m-ZrO2 followed by nitridation at 1123 K for 15 h under NH3 flow. The activity of the m-ZrO2/TaON composite for H, evolution from aqueous methanol solution is higher than that of either m-ZrO2 or TaON when loaded with nanoparticulate ruthenium as a H-2 evolution site. The highest activity is obtained using a composite prepared with a Zr/Ta molar ratio of 0.1. The optimized material also provides elevated activity when used as an H-2 evolution photocatalyst in Z-scheme overall water splitting in combination with Pt-loaded WO3 as an O-2 evolution photocatalyst and an IO3-/I- shuttle redox mediator. The improvement in activity is attributed to the suppression of surface defect formation by inhibiting tantalum reduction during nitridation.