Designing an active Ta3N5 photocatalyst for H2 and O2 evolution reactions by specific exposed facet engineering: a first-principles study

Abstract

The effects of native defects and exposed facets on the thermodynamic stability and photocatalytic characteristics of Ta₃N₅ for water splitting are studied by applying accurate quantum computations on the basis of density functional theory (DFT) with the range-separated hybrid functional (HSE06). Among the three explored potential candidates for O-enriched bulk Ta₃N₅ structures with substituted O at N sites and accompanied by interstitial O or Ta-vacancies, the first and third structures are relevant. The four possible (001), (010), (100) and (110) low Miller index exposed facets of Ta_(3−x)N_(5−y)O_y (y = 7x) are also explored, which show lower formation energies than those of Ta₃N₅. This highlights O occupation at N sites together with Ta vacancies as native defects in the prepared samples. The most appropriate facets for HER and OER are predicted based on the redox and transport characteristics. Our work predicts (001) and (110) facets only for HER, whereas the (010) facet is predicted for OER. Our findings indicate the importance of understanding the significance of various facets when preparing and testing new material photocatalysts for water splitting reactions.