Er3+-doped ZnO/ZnAl2O4 multi-phase oxides acting as near-infrared active photocatalyst

Doping lanthanide ions in metal oxides is an efficient way to develop visible and near-infrared (NIR) active photocatalysts. Herein, we present a method to develop NIR active photocatalyst via doping Er3+ into ZnO/ZnAl2O4 multi-phase oxides by isomorphous replacement of Al3+ with Er3+ during the preparation of Zn/Al-hydrotalcite-like compound, specifically, the calcination of the hydrotalcite-like compound at 900 °C. The as-prepared Er3+-doped catalyst and its precursor were characterized using X-ray diffraction technique, scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy and near-infrared-visible-ultraviolet diffused reflectance spectroscopy. It was found that the doping of Er3+ causes lattice expansion for ZnO and ZnAl2O4, and yields optical absorptions at visible and NIR light regions. The obtained Er3+-doped ZnO/ZnAl2O4 multi-phase oxides produce superoxide and hydroxyl radicals in the photocatalytic process, and show enhanced ultraviolet (UV) photocatalytic activity on degradation of methyl orange, compared to undoped ZnO/ZnAl2O4 multi-phase oxides. The Er3+-doped ZnO/ZnAl2O4 multi-phase oxides also possess visible and NIR light photocatalytic activities, and its photocatalytic activity is rather stable under UV, visible and NIR light irradiation. This work provides a new way for doping of lanthanide ions in metal oxides and designing full-spectrum photocatalysts.