Band Gap Engineering in Quadruple-Layered Sillén–Aurivillius Perovskite Oxychlorides Bi7Fe2Ti2O17X (X = Cl, Br, I) for Enhanced Photocatalytic Performance

Developing efficient photocatalyst for the photoreduction of CO2 and degradation of organic pollutants is an effective alternative to address increasingly serious energy problems and environmental pollution. Herein, the isostructural Sillén–Aurivillius oxyhalides, Bi7Fe2Ti2O17X (X = Cl, Br, and I; BFTOX), are fabricated for CO2 reduction and degradation of organic pollutants for the first time. Density functional theory (DFT) calculations show that the valence band maximum (VBM) of BFTOC and BFTOB is contributed by the dispersive 2p orbitals of O-atoms, providing the narrow band gap (Eg) and possibly the stability against self-decomposition deactivation. The photocatalytic activities of BFTOX are strongly affected by the halogens (Cl, Br, and I), namely, the BFTOCl sample displays outstanding activity improvement (3.74 μmol·g−1·h−1) for photocatalytic performance. This is mainly attributed to the high separation of charge carriers, small optical band gap, and extended optical absorption. This work focuses on affording a reference to develop efficient and stable photocatalysts from Sillén-Aurivillius layered oxyhalide materials.