Core/Shell Structured La- and Rh-Codoped SrTiO3 as a Hydrogen Evolution Photocatalyst in Z-Scheme Overall Water Splitting under Visible Light Irradiation

The effects of preparation methods, calcination times, and La doping concentrations on the crystallinity, visible light absorption, and photocatalytic water splitting performance of Rh- and La-codoped SrTiO3 (SrTiO3:La/Rh) were investigated. Applying a two-step solid state reaction in which SrTiO3 acted as a perovskite-type host produced core/shell structured SrTiO3:La/Rh, the surface of which was enriched with the dopants. La doping suppressed the formation of oxygen vacancies and inactive Rh4+ species. Under visible light irradiation (λ > 420 nm), SrTiO3:La/Rh exhibited 3.5 and 3.8 times higher rates of H2 evolution in an aqueous methanol solution and during redox-free Z-scheme overall water splitting in combination with Ir/CoOx/Ta3N5, respectively, compared to SrTiO3:Rh. The solar-to-hydrogen efficiency of the Z-scheme system as measured under illumination with simulated sunlight (AM1.5G) was found to have improved by a factor of 3.