Reinforced built-in electric fields and multichannel charge transfer in dual S-scheme heterojunctions for photocatalytic H2 evolution and H2O2 production

The efficient separation and migration of photogenerated charge carriers are crucial for enhancing photocatalytic performance. Constructing dual S-scheme heterojunctions is an effective strategy to reinforce the built-in electric field (IEF), rational modulation of charge transfer pathways, and consequently greatly enhanced charge separation and transport kinetics, leading to superior photocatalytic activity. Herein, a ternary dual S-scheme heterojunction, g-C 3 N 4 /ZnTCPP-HOFs/TiO 2 (gTZ-2), was successfully fabricated for photocatalytic H 2 evolution and hydrogen peroxide (H 2 O 2 ) production. Photocatalytic tests reveal that gTZ-2 delivers significantly improved activity, with H 2 and H 2 O 2 production rates reaching 17.21 mmol g −1 h −1 and 3.30 mmol g −1 h −1 , respectively, greatly outperforming the single-component and binary heterojunction counterparts. Such excellent photocatalytic performance originates from the enhanced IEF and the rationally constructed dual S-scheme charge-transfer pathway, which synergistically promotes the efficient migration and separation of photogenerated charge carriers. Combined with the Femtosecond transient absorption spectroscopy (fs-TAS), in situ X-ray photoelectron spectroscopy, Kelvin probe force microscopy, and density functional theory calculations, this work deeply reveals the charge transfer mechanism and prolonged carrier lifetime within the dual S-scheme heterojunction. This study provides a reliable and universal strategy for designing high-performance dual S-scheme heterojunctions with enhanced IEF and multi-channel electron transport avenues toward efficient solar energy conversion applications.