Modification of Visible-Light-Responsive Pb2Ti2O5.4F1.2with Metal Oxide Cocatalysts to Improve Photocatalytic O2Evolution toward Z-scheme Overall Water Splitting.

Abstract

The development of a highly active photocatalyst for visible-light water splitting requires a high-quality semiconductor material and a cocatalyst, which promote the migration of photogenerated charge carriers and surface redox reactions. In this work, cocatalyst loading on an oxyfluoride photocatalystPb2Ti2O5.4F1.2was applied to improve the water oxidation activity. Among the metal oxides examined, RuO2was found to be the most suitable, and the O2evolution activity depended on the preparation conditions of Ru/Pb2Ti2O5.4F1.2. The highest activity was obtained with RuCl3-impregnatedPb2Ti2O5.4F1.2, heated under a flow of H2at 523 K. The H2-heated Ru/Pb2Ti2O5.4F1.2showed an O2evolution rate ~13 times higher than the analogues without the H2treatment (e.g., RuO2/Pb2Ti2O5.4F1.2). Physicochemical analyses by means of X-ray absorption fine-structure spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and time-resolved-microwave-conductivity measurement indicated that the optimized photocatalyst contained partially-reduced RuO2species having ~5 nm in size, which effectively trapped the photogenerated charge carriers and promoted the oxidation of water into O2. The optimized Ru/Pb2Ti2O5.4F1.2was workable as an O2-evolving photocatalyst in Z-scheme overall water splitting, in combination of Ru-loaded, Rh-doped SrTiO3photocatalyst.