A Twin S-Scheme Artificial Photosynthetic System with Self-Assembled Heterojunctions yields Superior Photocatalytic Hydrogen Evolution Rate.

Designing heterojunction photocatalysts imitating natural photosynthetic systems has been a promising approach for photocatalytic hydrogen generation. However, in the traditional Z-Scheme artificial photosynthetic systems, the poor charge separation, and rapid recombination of photogenerated carriers remain a huge bottleneck. To rationally design S-Scheme (i.e., Step scheme) heterojunctions by avoiding the futile charge transport routes is therefore seen as an attractive approach to achieving high hydrogen evolution rates. Herein, we propose a twin S-scheme heterojunction involving graphitic C 3 N 4 nanosheets self-assembled with hydrogen-doped rutile TiO 2 nanorods and anatase TiO 2 nanoparticles. This catalyst shows an excellent photocatalytic hydrogen evolution rate of 62.37 mmol g -1 h -1 and high apparent quantum efficiency of 45.9% at 365 nm. The significant enhancement of photocatalytic performance is attributed to the efficient charge separation and transfer induced by the unique twin S-scheme structure. The charge transfer route in the twin S-scheme is confirmed by in-situ X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) spin-trapping tests. Femtosecond transient absorption (fs-TA) spectroscopy, transient-state surface photovoltage (TPV) and other ex-situ characterizations further corroborate the efficient charge transport across the catalyst interface. This work offers a new perspective on constructing artificial photosynthetic systems with S-scheme heterojunctions to enhance photocatalytic performance. This article is protected by copyright. All rights reserved.