Improved Photocatalytic O2 Evolution on a Sillén–Aurivillius Perovskite Oxychloride Bi6NbWO14Cl by Rh2O3 Additives and Surface Modifications

A Sillén–Aurivillius-type single-layered perovskite oxyhalide, Bi6NbWO14Cl, was recently reported as a stable and efficient O2-evolving photocatalyst for Z-scheme water splitting, even without any modifications. However, efforts have not yet been made to improve its photocatalytic activity. In this study, we synthesized a Bi6NbWO14Cl photocatalyst using Rh2O3 additives and modified its surface with Rh species to improve its photocatalytic activity. An appropriate amount of the Rh2O3 additive significantly enhanced the O2 evolution rate on Bi6NbWO14Cl from the aqueous AgNO3 solution, likely owing to enhanced charge transfer by the metallic Rh nanoparticles formed around the grain boundaries. In addition, surface modification with Rh species led to a further enhancement of the O2 evolution rate. The apparent quantum efficiency of the O2 evolution reached 11% at 420 nm, which is the best reported performance for oxyhalides prepared by solid-state reactions. These Rh species were characterized by X-ray absorption fine structure, X-ray photoelectron spectroscopy, and transmission electron microscopy, and their roles in the enhanced photocatalytic activities were discussed.