Elucidation of Rh-Induced In-Gap States of Rh:SrTiO3 Visible-Light-Driven Photocatalyst by Soft X‑ray Spectroscopy and First-Principles Calculations

• Published in: Journal of physical chemistry. C 2012-11, Vol.116 (46), p.24445-24448
• Main Authors: Kawasaki, Seiji, Akagi, Kazuto, Nakatsuji, Kan, Yamamoto, Susumu, Matsuda, Iwao, Harada, Yoshihisa, Yoshinobu, Jun, Komori, Fumio, Takahashi, Ryota, Lippmaa, Mikk, Sakai, Chikako, Niwa, Hideharu, Oshima, Masaharu, Iwashina, Katsuya, Kudo, Akihiko
• Format: Article
• Language: English
• Subjects: Catalysis; Catalysts: preparations and properties; Chemistry; Exact sciences and technology; General and physical chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp3082529

The occupied and unoccupied in-gap electronic states of a Rh-doped SrTiO3 photocatalyst were investigated by X-ray emission spectroscopy and X-ray absorption spectroscopy for different Rh impurity valence states and doping levels. An unoccupied midgap Rh4+ acceptor state was found 1.5 eV below the SrTiO3 conduction band minimum. Both Rh4+ and Rh3+ dopants were found to have an occupied donor level close to the valence band maximum of SrTiO3. The density of states obtained from first-principles calculations show that all observed spectral features can be assigned to electronic states of substitutional Rh at the Ti site and that Rh:SrTiO3 is an unusual titanate compound with a characteristic p-type electronic structure. The Rh doping results in a large decrease of the bandgap energy, making Rh:SrTiO3 an attractive material for use as a visible-light-driven H2-evolving photocatalyst in a solar water splitting reaction.