Subtle structure matters: boosting surface-directed photoelectron transfer the introduction of specific monovalent oxygen vacancies in TiO.

Oxygen vacancies (O) are widely considered to play crucial roles in photocatalysis, but how and why they contribute to improved performances remains controversial. In this work, we studied the promotional effect of O on photoelectron transfer in TiO, using first-principles density functional theory calculations with correction for on-site Coulomb interactions. We explicitly identified three types of O with different charge states (, charge-neutral , monovalent , divalent O) electronic structure analysis. Electron transfer energy calculations revealed that the ionized O in anatase TiO are able to collect excess electrons whereas those in the rutile phase are not. The presence of ionized O further endows anatase TiO with directional electron transfer along the [100] orientation, in favor of anatase TiO(101) for photocatalytic reduction surpassing the (001) termination. After examining various combination modes of ionized O involving different charge states and spatial distributions, we demonstrated that the vertical chain in anatase TiO(101) is the most catalytically effective O pattern in TiO. These results signify the importance of subtle defects in photocatalysis and may assist future photocatalyst design toward higher photocatalytic efficiency.