Architectural engineering of yolk-shell TiO2@g-C3N4 S-scheme heterojunctions via a peroxidation strategy for enhanced photocatalytic hydrogen evolution

The widespread application of TiO 2 in photocatalytic hydrogen (H 2 ) evolution is severely hampered by its wide bandgap and rapid charge carrier recombination. Herein, a well-defined yolk-shell TiO 2 @g-C 3 N 4 S-scheme heterojunction was rationally engineered via a facile peroxidation-assisted strategy to significantly enhance photocatalytic hydrogen evolution. The synthesis included stepwise fabrication of a TiO 2 @SiO 2 @g-C 3 N 4 dual-core–shell intermediate, followed by selective etching of the sacrificial SiO 2 interlayer to form the tailored hollow structure. This unique architecture enhances light harvesting via internal scattering, shortens carrier migration distance and facilitates charge separation relying on the spatially confined ultrathin g-C 3 N 4 shell. The optimized TCN-2 photocatalyst achieves a prominent H 2 evolution rate of 134 μmol·g −1 ·h −1 under visible light, which is 6.4 times that of pure TiO 2 . Systematic characterizations (XRD, XPS, TEM, UV–Vis DRS, PL, TRPL, photoelectrochemical and Mott-Schottky analyses) verify the successful heterojunction formation, efficient interfacial charge transfer and favorable internal electric field for S-scheme carrier migration. This work offers a controllable strategy for advanced yolk-shell heterostructures and highlights architectural engineering’s pivotal role in realizing photonic-electronic synergy for high-efficiency solar fuel generation.