Efficient Photocatalytic Hydrogen Production over Rh-Doped Inverse Spinel Zn2TiO4

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. Graphical Doped semiconductor : Rh doping is an efficient approach to endow wide band gap semiconductor Zn 2 TiO 4 with visible-light responses. Photocatalytic hydrogen production from water was greatly improved after Rh doping both under full-range and visible-light illumination. DFT calculations reveal the critical role of Rh in forming a new valence band. The high photocatalytic activity after doping can be understood as a result of more light absorption as well as improved surface hydrophilicity.