In Situ Phase-Induced Spatial Charge Separation in Core-Shell Oxynitride Nanocube Heterojunctions Realizing Robust Solar Water Splitting

Efficient spatial charge separation is critical for solar energy conversion over solid photocatalysts. The development of efficient visible-light photocatalysts has been of immense interest, but with limited success. Here, multiband core-shell oxynitride nanocube heterojunctions composed of a tantalum nitride (Ta3N5) core and nitrogen-doped sodium tantalate (NaTaON) shell have been constructed via an in situ phase-induced etching chemical strategy. The photocatalytic water splitting performance of sub-20-nm Ta3N5@NaTaON junctions exhibits an extraordinarily high photocatalytic activity toward oxygen and hydrogen evolution. Most importantly, the combined experimental results and theoretical calculations reveal that the strong interfacial Ta-O-N bonding connection as a touchstone among Ta3N5@NaTaON junctions provides a continuous charge transport pathway rather than a random charge accumulation. The prolonged photoexcited charge carrier lifetime and suitable band matching between the Ta3N5 core and NaTaON shell facilitate the separation of photoinduced electron-hole pairs, accounting for the highly efficient photocatalytic performance. This work establishes the use of (oxy)nitride heterojunctions as viable photocatalysts for the conversion of solar energy into fuels.