N-Promoted Ru/TiO single-atom catalysts for photocatalytic water splitting for hydrogen production: a density functional theory study.

We propose a universal dimer-doping strategy to improve the photocatalytic water splitting activity of Ru/TiO single-atom catalysts, in which the N atom is simultaneously doped. First-principles calculations show that the N dopants promote the substitution of Ti with Ru on the anatase TiO(101) surface by chemical bonding between Ru and N, and increase the stability of the system. Isolated Ru atoms act as active sites for the reduction of protons, and Ru-N/TiO has a hydrogen evolution activity comparable to that of Pd. The impurity bands within the band gap lead to a significant red-shift of the absorption edge towards the visible region, improving the photoabsorption and photocatalytic performance of TiO under sunlight. The reason is the charge compensation effect localized to the doped Ru-N dimers. We expect that this generic scheme that simultaneously realizes band-structure tailoring and reaction control also applies to other single-atom loaded oxide-based photocatalytic systems.