Synthesis, structure and photocatalytic activity of layered LaOInS2

Abstract

Indium oxychalcogenides would be attractive semiconductors considering the practical use of indium oxides and sulfides such as indium–tin oxides (ITO) and copper–indium–gallium diselenides (CIGS). In this work, a novel layered indium oxysulfide, LaOInS₂, was synthesized by a metathesis reaction between LaOCl and NaInS₂. Synchrotron X-ray diffraction showed that LaOInS₂ consisted of alternately stacked rocksalt-type In–S and PbO-type La–O layers. The InS₆ octahedron had split In sites with abnormally large anisotropic atomic displacement factors. LaOInS₂ was found to be a direct semiconductor. Density functional theory calculations exhibited well-dispersed bands composed of In 5s/5p and S 3p/O 2p orbitals with a band gap of ∼2.4 eV, which was close to the experimental value estimated by optical absorption (2.64 eV). Under visible light irradiation this visible-light absorption, LaOInS₂ exhibited photocatalytic activity for H₂ and O₂ evolution from water with the aid of Pt and IrO₂ cocatalysts, respectively.