Effect of Compensated Codoping on the Photoelectrochemical Properties of Anatase TiO2 Photocatalyst

An effective codoping approach is described to modify the photoelectrochemical properties of anatase TiO2 by doping with nonmetal (N or C) and transition metal (Nb or Ta) impurities. Here, compensated and noncompensated codoped TiO2 systems are constructed with different proportions and dopant species, and then their dopant formation energies and electronic properties are calculated to study the stability and visible-light photoactivity by first-principles density functional theory incorporating the LDA+U formalism, respectively. The calculated results demonstrate that the codoping with transition metals facilitates the enhancement of the concentration of p-type dopants (N and C) in the host lattice. Especially, both 1:2 compensated Nb/C/Nb and Ta/C/Ta codopings not only reduce the energy gap to enhance the optical absorption and eliminate the local trapping to improve carrier mobility and conversion efficiency but also do not lower the reduction potential of the conduction band edge. Our designated strategies of codoped anatase TiO2 simultaneously meet the criteria for water splitting. It should be pointed out that, to be successful, the proper proportion of transition metal and nonmetal impurities in the host lattice should be controlled so that reasonable photoelectrochemical properties can be achieved.