Efficient Photocatalytic Hydrogen Production over Rh-Doped Inverse Spinel Zn2TiO4

Abstract Introducing foreign elements is an appealing means to endow wide band gap semiconductors with visible‐light responses. Here, we investigated a series of Rh‐doped Zn 2 TiO 4 as water reduction photocatalysts. Our results show that Rh doping is effective to improve the visible‐light response as well as surface hydrophilicity of Zn 2 TiO 4 . Efficient photocatalytic hydrogen evolution was observed after Rh doping and was found to be compositional dependent. The best performance was recorded for sample Zn 2 Ti 0.96 Rh 0.04 O 4 , with an apparent quantum efficiency of ≈0.74 % under full‐range irradiation ( λ ≥250 nm) and ≈0.25 % under visible‐light irradiation ( λ ≥420 nm). The light absorption and surface hydrophilicity are likely the controlling factors for the better activity. Theoretical calculations suggest that Rh doping is responsible for a band gap reduction and is due to a newly formed valence band composed mainly of Rh 4d orbitals at the top of the original valence band. The visible‐light activity can be attributed to the electron excitations from this new valence band to the conduction band.