Harnessing Visible Light: Unraveling the Photocatalytic Water Splitting Activity of Ir–TiO2

Abstract

The quest to enhance the photocatalytic properties of TiO₂ for hydrogen evolution in the visible region has necessitated its modification through various strategies. In this study, a one-pot solvothermally synthesized iridium-decorated titanium dioxide (Ir–TiO₂) exhibits enhanced photochemical properties for splitting water in visible light. By varying the amount of Ir precursors, Ir-doped TiO₂ and IrO₂ composites with TiO₂ were formed. Density functional theory (DFT) calculations reveal that Ir has localized d and f orbitals and that its oxide exhibits metallic character. When Ir replaces Ti as the dopant, energy levels appear near the Fermi level. At lower Ir concentrations, Ti still dominates, and Ti 3d hybridizes with Ir 5d, while O 2p interacts with Ir 5p, contributing to the narrowing of the band gap and modification of the chemical and electronic properties of TiO₂. Photocatalytic hydrogen evolution experimental results revealed that Ir–TiO₂ exhibits high activity with a yield of 1636.7 μmol h^–1 g^–1 compared to pristine (238.0 μmol h^–1 g^–1) and commercial (241.0 μmol h^–1 g^–1) TiO₂. This can be attributed collectively to the reduction of the band gap for effective light absorption, a high surface area, and efficient charge transfer. The excellent recyclability and reusability of our materials demonstrate their long-term applicability as catalysts.