Insights into the Most Suitable TiO2 Surfaces for Photocatalytic O2 and H2 Evolution Reactions from DFT Calculations

TiO2 is considered as one of the most common photocatalysts for UV light-driven photocatalysis. We present here the effect of exposed facets on the photocatalytic features of anatase and rutile TiO2 crystals using first-principle computations based on the density functional theory (DFT). The four possible low-Miller-index (110), (101), (100), and (001) surfaces of each crystalline phase are investigated. The most suitable facets for hydrogen and oxygen evolution reactions (HER and OER, respectively) are identified on anatase and rutile TiO2 from the combination of the anisotropic redox and charge carrier transport properties. Our study demonstrates the (110) anatase surface as the most suitable candidate for OER, followed by the (101) surface, whereas the (001) anatase surface is predicted as the most suitable candidate for HER. For rutile, the two (110) and (101) surfaces are predicted as the most suitable candidates for OER, while no suitable surface candidate is found for HER in line with the experimental observations showing better activity for HER using anatase than rutile. These findings will guide experimentalists to carefully design (110)- and (001)-oriented anatase TiO2 material samples for improved photocatalytic water oxidation and proton reduction.