Predicting the Most Suitable Surface Candidates of Ta3N5 Photocatalysts for Water-Splitting Reactions Using Screened Coulomb Hybrid DFT Computations

Ta3N5 is one of the mostly used photocatalysts for visible light-driven water splitting. Using accurate first-principles calculations based on the density functional theory (DFT) with the screened non-local hybrid HSE06 functional, we present a comprehensive study on the effect of exposed facets on this material for H2 and O2 evolution reactions. We investigated the impact of partial or complete surface oxidation on the stability, electronic, and redox features of Ta3N5. The four possible explored (110), (100), (001), and (010) low Miller index surfaces show lower formation energies for Ta3N(5-x)Ox than the pure Ta3N5 ones, highlighting the presence of O impurities as observed experimentally. By combining their anisotropic electronic, charge-carrier transport, and redox features, our study predicts (110) and (001) surfaces as appropriate candidates only for HER, whereas the (010) surface is the only suitable candidate for OER. These fundamental results highlight the relevance of different facets and open doors for effective design of active Ta3N5-based photocatalysts with predominant (110), (001), and (010) facets for solar-driven overall water-splitting reactions by controlling and tuning the morphology in order to get the desired surfaces.