Donor-acceptor codoping effects on tuned visible light response of TiO2

The monodopants in TiO2 can improve the visible light harvest of TiO2 through the modification of the electronic structures and defects generation. However, most dopants will introduce extra electrons or holes in the system for the unbalanced charge and the defects also act as recombination centers for photo excited electron-hole pairs. The charge compensated codoping technique with donor and accepter is expected to overcome the shortcomings of the monodoping technique. The review collected some typical reports on the codoping effects in TiO2 for high performance photocatalysts through the enhancement of visible light harvest. Theoretical calculation predicts some donor-acceptor codoped TiO2 as practical photocatalyst for water purification or water splitting. In addition to the doping induced light response variation, the experimental results also reveal that the dopants and micromorphology show comprehensive influence on the photocatalytic performance in terms of photon absorption, exciton separation, carrier diffusion, carrier transport, catalytic efficiency and mass transfer phenomena. The review includes three sections to summarize metal/metal codoping, non-metal/non-metal codoping, and metal/non-metal codoping effects on visible light response and one more section to discussion the collaborative effects of bandgap, flat band potential, charge transport, charge transfer, surface potential, and concentration of surface active sites on the photocatalytic reaction.