Particulate photocatalyst sheets based on non-oxide semiconductor materials for water splitting under visible light irradiation

Abstract

Particulate photocatalyst sheets based on a hydrogen evolution photocatalyst (HEP) and an oxygen evolution photocatalyst (OEP) embedded in a conductive material can realize efficient and scalable water splitting. However, existing sheet systems involve photocatalytic materials with absorption edge wavelengths (λ_abs) of approximately 500 nm. Thus, the development of sheet systems based solely on photocatalysts with longer absorption edge wavelengths is essential for obtaining solar-to-hydrogen energy conversion efficiency required for practical applications. In this study, we present a photocatalyst sheet system based on Ga-doped La₅Ti₂Cu_0.9Ag_0.1S₅O₇ (Ga-LTCA, λ_abs = 710 nm) as the HEP and LaTiO₂N (λ_abs = 600 nm) loaded with cobalt oxide (CoO_x) as the OEP, both embedded in a Au layer by particle transfer (Ga-LTCA/Au/LaTiO₂N). Ga-LTCA/Au/LaTiO₂N sheets modified with Rh species evolved hydrogen and oxygen simultaneously under visible light irradiation (λ > 420 nm). The loading of CoO_x onto LaTiO₂N was found to be essential for successful water splitting, as was the choice of pH values during water splitting. The roles of CoO_x and other factors in determining the water splitting activity of the Ga-LTCA/Au/LaTiO₂N sheets are described herein, based on the photoelectrochemical properties of LaTiO₂N photoanodes.