Au-modified hollow TiO2 nanobowl@ZnIn2S4 S-scheme heterostructures for coupled photocatalytic hydrogen evolution and selective benzylamine oxidation

The concurrent generation of clean hydrogen fuel and value-added organic compounds through photocatalysis offers a promising pathway for solar-to-chemical conversion. Here, we present a ternary Au-mediated S-scheme heterostructure comprising hollow TiO 2 nanobowls (HTNB), vertically aligned ZnIn 2 S 4 (ZIS) nanosheets, and interfacially confined Au nanoparticles. The hollow TiO 2 scaffold, fabricated via a green and scalable electrospray method, shortens carrier diffusion paths, while the direct S-scheme junction preserves strong redox potentials. Embedded Au nanoparticles at the HTNB/ZIS interface act as directional electron mediators, enabling cascade charge transfer (TiO 2 → Au → ZIS) and suppressing recombination. The optimized HTNB/Au@ZIS achieves a remarkable H 2 evolution rate of 42.27 mmol g −1 h −1 with an apparent quantum efficiency of 59.5 % at 380 nm under simulated solar light, among the highest reported for TiO 2 /ZIS systems. In a sacrificial-free system, it simultaneously produces 4.48 mmol g −1 h −1 H 2 and 4.05 mmol g −1 h −1 N-benzylidenebenzylamine with > 99 % selectivity. Comprehensive spectroscopic, electrochemical, and EPR analyses confirm the Au-mediated S-scheme charge-transfer mechanism. This work demonstrates a generalizable interfacial-engineering strategy for coupling oxidative and reductive photocatalysis, advancing the design of efficient dual-functional photocatalysts for solar-to-chemical energy conversion.