Study the high photocatalytic activity of vanadium and phosphorus co-doped TiO2 from experiment and DFT calculations

The origin of exceptionally high photocatalytic activity of phosphorus and vanadium (P/V) co-doped TiO2 under solar-light irradiation have been investigated by using X-ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflectance spectra combined with density functional theory (DFT) calculations. XPS experimental results demonstrated that a portion of the dopant P(P−3) ions were implanted into the crystalline lattice of P/V co-doped TiO2 and closed proximity V dopants at substitution farthermost Ti atom, forming [Psub.−O−V] structural units. On other hand, according to a new “noncompensated” codoping concept base on the DFT calculations, we found P substituted O (No. 1 position) and V substituted farthermost Ti (No. 7 position) were favorable in Ti-rich conditions, synchronously, the defects formation energy of P/V co-doped TiO2 was minimum only −1.383 eV, the formation energies were higher at substitutional-O and Ti site under O-rich than Ti-rich conditions. Calculated dopant energy levels of P/V co-doped TiO2 were 0 and 1.875 eV at the top of valence band and the bottom of conduction band respectively, the [Psub.−O−V] structural units were responsible for trapping the photoinduced electrons, which prolongs the life of the photoinduced charge carriers and eventually leads to a remarkable enhancement in the photocatalytic activity, the calculation results were consistent with the experiment results. These findings are expected to be crucial for understanding the roles of P and V dopants and their synergistic effect in numerous titaniamediated photocatalytic reactions.