A multiple core-shell heterostructure Rh-Rh modified TaO@TaON@TaN nanophotocatalyst was successfully constructed through nitriding Rh-doped TaO nanoparticles, which exhibited a much higher carrier separation efficiency about one order of magnitude higher than the TaO@TaN precursor, and thus an excellent visible light photocatalytic H-evolution activity (83.64 μmol g h), much superior to that of Rh anchored TaO@TaON (39.41 μmol g h), and improved stability due to the residual Rh-O/N in the TaN 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/TaN Schottky junction and double n-n TaN/TaON/TaO 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 TaN-based photocatalysts for solar energy conversion is provided by constructing double n-n mutant heterojunctions.