Oxides with a d0 electron configuration, with TiO2 as the most notable example, have attracted a lot of interest as working materials for photo-catalytic splitting of water.The band gap is one of the most critical parameters that determine the photo-catalytic activity of the material.However, the most widely used first-principle method, density functional theory (DFT) in local density or generalized gradient approximation (LDA/GGA), tends to severely underestimate the band gap.