NNaTaO₃@Ta₃N₅ Core-Shell Heterojunction with Controlled Interface Boosts Photocatalytic Overall Water Splitting

Ta₃N₅ is a promising material for photocatalytic hydrogen production from water because of its suitable band structure for both solar energy collection and overall water splitting, while its application is restricted by severe charge recombination as well as non-equilibrium redox capabilities. Herein, atomic-scale N-doped NaTaO₃@Ta₃N₅ (NNaTaO₃@Ta₃N₅) core-shell cubes prepared by nitridation of cubic NaTaO₃ are reported. The core-shell heterojunction cubes present efficient and stoichiometric evolution of H₂ and O₂ from photocatalytic overall water splitting, with a quantum efficiency of 2.18% at 550 nm without any cocatalyst. The success relies on the Ta₃N₅ shell having a thickness of only ≈5 nm which enables increased lifetimes of the photogenerated charges. Moreover, the core-shell heterojunction shows a type-I band alignment that can steer smooth charge flow from NNaTaO₃ to Ta₃N₅, particularly with the assistance of the shared communal Ta atoms at the interface. This efficiency can be further improved to 6.28% by in situ deposition of a Rh@Cr₂O₃ core-shell cocatalyst, which is among the highest reported values over Ta₃N₅-based photocatalyst. This study offers a promising pathway for the construction of well-defined heterojunctions with manipulated charge transfer behavior for photocatalytic overall water splitting.