Ab-initio DFT Calculations of La₅Ti₂CuS₅O₇ as a Photocatalytic Material for Water Splitting

Abstract

La₅Ti₂Cu_1-xAg_xS₅O₇, the solid solution of La₅Ti₂CuS₅O₇ and La₅Ti₂AgS₅O₇, is a candidate of photocatalysts for sunlight-driven water splitting. It is known that La₅Ti₂Cu_0.9Ag_0.1S₅O₇ has a narrower band gap than La₅Ti₂CuS₅O₇ and La₅Ti₂AgS₅O₇. In this study, density functional theory (DFT) calculation was performed to analyze the band structure and effective mass of La₅Ti₂Cu_1-xAg_xS₅O₇ solid solutions. The band gap of La₅Ti₂Cu_0.75Ag_0.25S₅O₇ was calculated to be narrower than those of La₅Ti₂CuS₅O₇ and La₅Ti₂AgS₅O₇, which was qualitatively consistent with the experimental observation. The effective mass for electron was also estimated from the band structure to be smaller in the b-axis direction than in the other directions.