Optimizing photoelectrochemical properties of TiO₂ by chemical codoping

First-principles calculations reveal potentially optimal photoelectrochemical activity of anatase TiO₂ by means of (C, S), (C, Se), or (N, P) codoping. It is found that the absorption edge is substantially redshifted to visible regime with overall spectra considerably better than monodoped TiO₂. The resulting optical gap straddle the redox potentials of H₂ O remarkably well. The reason for the significant improvements is the direct chemical bonding between the codopants. We expect this generic band-structure tailoring scheme also applies to other photocatalytic systems and beyond.