Study on mechanism of enhanced photocatalytic performance of N-doped TiO₂/Ti photoelectrodes by theoretical and experimental methods

Several kinds of N-doped/undoped TiO₂ photoelectrodes with different nanostructures have been successfully prepared by anodization method and plasma-based ion implantation (PBII) technique. The morphology and structure of as-prepared photoelectrodes were studied by scanning electron microscopy, X-ray diffraction, and ultra violet/visible light diffuse reflectance spectra. Electronic structure and optical properties were calculated by means of first-principle. Photocatalytic (PC) and photoelectrocatalytic (PEC) performance were measured by the decomposition of terephthalic acid (TA) and Rhodamine B under xenon light illumination. Theoretical calculation results demonstrated that crystal phases have great influence on the electric and optical properties, and N-doped TiO₂ photoelectrodes have isolated N_2P impurity states nearby the top of the valence band. The optical properties and UV/Vis analysis confirmed that the absorption edge of N–TiO₂ emerged red-shift and high photosensitivity. The discrepancy of PC and PEC performance of as-prepared TiO₂ photoelectrodes were ascribed to band gap narrowing, N_2p impurity states, self-semiconductor coupling effect, and long-range ordered orientation of photogenerated carries originated from applied electric field.