Improved Photocatalytic O<sub>2</sub> Evolution on a Sillén–Aurivillius Perovskite Oxychloride Bi<sub>6</sub>NbWO<sub>14</sub>Cl by Rh<sub>2</sub>O<sub>3</sub> Additives and Surface Modifications
Hajime Suzuki, Takanori Takashima, Osamu Tomita, Tomoki Kanazawa, Shunsuke Nozawa, Kosaku Kato, Akira Yamakata, Kouichi Nakashima, Akinori Saeki, Ryu Abe
Abstract
A Sillén–Aurivillius-type single-layered perovskite oxyhalide, Bi 6 NbWO 14 Cl, was recently reported as a stable and efficient O 2 -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 Bi 6 NbWO 14 Cl photocatalyst using Rh 2 O 3 additives and modified its surface with Rh species to improve its photocatalytic activity. An appropriate amount of the Rh 2 O 3 additive significantly enhanced the O 2 evolution rate on Bi 6 NbWO 14 Cl from the aqueous AgNO 3 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 O 2 evolution rate. The apparent quantum efficiency of the O 2 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.