Regulating carrier pathways from type-II to S-scheme in g-C₃N₄-based heterojunctions for synchronous tetracycline...

Simultaneously achieving pollutant degradation and hydrogen production from wastewater via photocatalysis is challenging. S-scheme heterojunctions, which maintain strong redox ability and promote charge carrier separation, are a research hotspot. We demonstrate that trace ordered Pd nanochannels can reconfigure a type-II (g-C₃N₄/TCPP_{-1 %}) into an S-scheme heterojunction (g-C₃N₄/PdTCPP_{-1 %}), thereby achieving synchronous tetracycline degradation and hydrogen evolution with remarkable efficiency. The ordered Pd nanochannel within the self-assembled PdTCPP nanotube acted as a directional electron channel to precisely convert the heterojunction from type-II to an S-scheme configuration, with in-situ XPS and photodeposition experiments confirming spatially separated charge accumulation and directional transfer pathways. The results showed that g-C₃N₄/TCPP_{-1 %} and g-C₃N₄/PdTCPP-_{1 %} could achieve 76.07 % and 84.66 % degradation efficiency for TC within 120 min under visible light irradiation. Notably, replacing deionized water with TC wastewater enhanced the photocatalytic hydrogen evolution rate of g-C₃N₄/PdTCPP_{-1 %} by 2.2-fold that from 517.7 to 1138.2 μmol g^-1·h^-1, whereas g-C₃N₄/TCPP_{-1 %} exhibited only a marginal increase from 181.1 to 211.3 μmol g^-1·h^-1 under identical conditions. We report a pioneering strategy for synchronous environmental and energy challenges by the direct conversion of a type-II to an S-scheme heterojunction through engineered Pd nanochannels, paving the way for efficient pollutant degradation and renewable H₂ production.