Rh nanospheres anchored TaON@Ta2O5 nanophotocatalyst for efficient hydrogen evolution from photocatalytic water splitting under visible light irradiation

Rh nanospheres anchored TaON@Ta₂O₅ with shell-core structure was synthesized from in-situ Rh³⁺-doped Ta₂O₅ by one-step high-temperature ammonolysis, which exhibited efficient visible light photoactivity for H₂-evolution (39.41 μmol·g⁻¹·h⁻¹), much higher than unmodified Ta₃N₅@Ta₂O₅ (21.75 μmol·g⁻¹·h⁻¹). Rh-modifying inhibited the phase transformation from TaON to Ta₃N₅ during the nitridation process, and increased the specific surface area and active sites, and extended the optical absorption throughout visible light region due to localized surface plasmon resonance (LSPR) effect. Relative intensities of peaks at 827 cm⁻¹ for Ta–O bonds increased with increasing Rh-modifying amounts, which was beneficial to improving the stability. Notably, constructing novel Rh/TaON/Ta₂O₅ heterojunctions including a Rh/TaON Schottky junction and an n-n TaON/Ta₂O₅ mutant heterojunction facilitated photogenerated carriers directed transfer from inner to surface active sites, and decreased travel distance of charge carriers, and formed built-in electric fields to accelerating charge separation. Synergetic effects of the enhanced photocatalytic H₂-evolution activity were discussed in detail. This work provided a promising strategy to further design and develop efficient and stable Ta-based photocatalysts for solar water splitting.