Defect Chemistry of Er3+-Doped TiO2 and Its Photocatalytic Activity for the Degradation of Flowing Gas-Phase VOCs

A series of Er-doped TiO2 photocatalysts, using Er(NO3)3·6H2O precursor ranging from 0.5 to 2 mol %, were synthesized via sol–gel method with titanium(IV) isopropoxide solution as reactant. The structure and properties of as-prepared samples were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, UV–vis spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy, thermogravimetric analysis, photoluminescence, electrochemical impedance spectroscopy, and photocurrent. The as-synthesized Er-doped TiO2 nanoparticles demonstrated improved photocatalytic activities for the photodegradation of selected volatile organic compounds, including acetaldehyde, o-xylene, and ethylene. Additionally, high photodegradation of acetaldehyde was recorded in the visible region (λ > 420 nm). XPS analysis revealed that a handful of Er in anatase TiO2 was presented in the form of Er2O3, which benefited by increasing the specific surface area rangin...