Composition dependence of structural, optical, and photoelectrochemical properties of nanocrystalline neodymium-doped titania photocatalyst

Neodymium-doped titanium dioxide (Nd/TiO₂) films with different Nd concentration x from 2 to 10% are fabricated on silicon by chemical solution deposition and a subsequent cathodic electrochemical process using neodymium nitrate solution as the Nd source. The Nd dopant effects on the structural, optical, electrical, and photoelectrochemical properties of the Nd/TiO ₂ films are investigated by X-ray diffraction, ultraviolet Raman scattering, UV-vis diffuse reflectance spectra (DRS), and electrochemical methods at room temperature. XRD shows the polycrystalline anatase phase with Nd atoms incorporated into the TiO₂ matrix. The grain size decreases with increasing Nd concentrations. The intensity of the Raman-active mode B _1g increases with Nd concentration. The diffuse reflection absorption spectra (DRS) indicate that the absorbance edge of all the Nd/TiO₂ samples shifts to the visible region. The Nd dopant decreases the band gap of TiO₂ consequently enhancing the visible light absorption ability of the photocatalyst. The photoelectrochemical results indicate that in the same electrolyte, Nd can significantly enhance the photoconversion efficiency of the TiO₂ electrode as well as the photocurrent density. The Nd/TiO ₂ electrode shows higher efficiency in photoelectrocatalytic (PEC) degradation of p-nitrophenol (PNP) than the undoped TiO₂ electrode under the same conditions.