Electronic Structure of Lanthanide-Doped Bismuth Vanadates: A Systematic Study by X-ray Photoelectron and Optical Spectroscopies

Monoclinic BiVO4 has emerged in recent years as one of the most promising materials for photocatalytic evolution of oxygen under solar irradiation. However, it is in itself unable to phototcatalyze reduction of water to hydrogen due to the placement of the conduction band edge below the potential required for H2O/H2 reduction. As a consequence, BiVO4 only finds application in a hybrid system. Very recently, tetragonal lanthanide-doped BiVO4 powders have been shown to be able to both reduce and to oxidize water under solar irradiation, but to date there has been no comprehensive study of the electronic properties of lanthanide-doped bismuth vanadates aimed at establishing the systematic trends in the electronic structure in traversing the lanthanide series. Here, the accessible family of lanthanide-doped BiVO4 quaternary oxides of stoichiometry Bi0.5Ln0.5VO4 (Ln = La to Lu, excluding Pm) has been studied by X-ray powder diffraction, X-ray photoemission spectroscopy, and diffuse reflectance optical spectros...