Construction of a ternary spatial junction in yolk–shell nanoreactor for efficient photo-thermal catalytic hydrogen generation

[Display omitted] •A novel C@TiO2/TiO2-x yolk–shell nanoreactor was prepared by a facile strategy.•The ternary spatial junctions boost the separation of photogenerated carriers.•Bifunctional carbon spheres as nanoheater to induce the heat built-up in nanoreactor.•Surface-anchored TiO2-x nanoparticles afford the active sites for proton reduction.•This ternary catalyst exhibited remarkably enhanced photo-thermal HER performance. Highly efficient solar‐to‐hydrogen (H2) conversion depends crucially on the light-harvesting capability, cumulative cascade efficiency of photo-induced carriers, and surficial vibrant kinetics of photocatalysts. Herein, a spatially ternary carbon nanospheres@TiO2/reduced TiO2 (denoted as C@TiO2/TiO2-x) yolk–shell (YS) nanoreactor is proposed as a model solar water splitting system, in which an excellent photothermal conversion is achieved by the YS nanoreactor with carbon core as the nanoheater and its light absorption range is extended to the longer wavelength of even near‐infrared light. Spatial inside-out junctions in the nanoreactor were designed to frame multiple-level charge transfers with the Ti–O–C channel as charge transport bridge. Surface oxygen vacancy defects (OVs) induced by Ti3+ self-doping accelerate the mass transfer, trap the photo-induced electrons, and afford the active sites for proton reduction. Therefore, benefiting from the dual contributions of the heat built-up and ternary spatial junctions in the C@TiO2/TiO2-x YS nanoreactor, its photo-thermal catalytic H2 conversion activity (3667 μmol h−1 g−1) has been remarkably enhanced at least 22-fold under simulated sunlight irradiation (AM 1.5G) without the use of noble metal cocatalysts. This YS spatial junction construction strategy for cascade electron transfer in nanoreactors may be further applied to other photo-thermal catalysts for enhanced solar-to-fuel conversions.