Constructing Rh-Rh 3+ modified Ta 2 O 5 @TaON@Ta 3 N 5 with special double n-n mutant heterojunctions for enhanced photocatalytic H 2 -evolution.

A multiple core-shell heterostructure Rh-Rh 3+ modified Ta 2 O 5 @TaON@Ta 3 N 5 nanophotocatalyst was successfully constructed through nitriding Rh 3+ -doped Ta 2 O 5 nanoparticles, which exhibited a much higher carrier separation efficiency about one order of magnitude higher than the Ta 2 O 5 @Ta 3 N 5 precursor, and thus an excellent visible light photocatalytic H 2 -evolution activity (83.64 μmol g -1 h -1 ), much superior to that of Rh anchored Ta 2 O 5 @TaON (39.41 μmol g -1 h -1 ), and improved stability due to the residual Rh-O/N in the Ta 3 N 5 shell layer. Rh-modifying significantly extended light absorption to the overall visible region. Localized built-in electric fields with hierarchical potential gradients at the multiple interfaces including a Rh/Ta 3 N 5 Schottky junction and double n-n Ta 3 N 5 /TaON/Ta 2 O 5 mutant heterojunctions, drove charge carriers to directionally transfer from inside to outside, and efficiently separate. Enhanced photoactivity was ascribed to a synergetic effect of improved light absorption ability, increased carrier separation efficiency, and accelerated surface reaction. A promising strategy of developing excellent Ta 3 N 5 -based photocatalysts for solar energy conversion is provided by constructing double n-n mutant heterojunctions.