Photocatalytic Activity and Hole-Scavenging Behaviors on Rutile TiO₂(100) Surfaces: A Theoretical Study

A rutile TiO₂(100) surface usually shows better photoactivity than other surfaces, and its mechanism is not well understood yet. In this work, we found larger charge accumulation on its bridging oxygen/adsorbents and lower symmetry of its surface Ti atoms. This enables (100) a better surface to accommodate the hole, which could be one key reason for its high photoactivity. Interestingly, the localized hole on the (100) surface can be reliably simulated using a density functional theory (DFT) method without Hubbard U corrections, which affords an unbiased platform to study the hole-scavenging behavior for extensive adsorbents and functional groups. Then, the hole-mediated proton dissociations of water, alcohol, amine, and alkane on the (100) surface have been studied in detail. The hole-scavenging ability of the groups is in the order hydroxyl < alkoxyl < aminyl < alkyl. Moreover, we found a good correlation between the hole-scavenging ability and the density of states. With this correlation, we predict that the facet hole-scavenging ability for most groups is in the order rutile (100) > anatase (101) > rutile (110) > rutile (001), which is in good agreement with the experimental observations and would provide suggestions for further photocatalytic studies.