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/TiO2 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 B1g 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/TiO2 electrode shows higher efficiency in photoelectrocatalytic (PEC) degradation of p-nitrophenol (PNP) than the undoped TiO2 electrode under the same conditions.