Precise construction of S-scheme and dual Schottky junctions in g-C$_3$N$_5$/TiO$_2$-Ov@Ti$_3$C$_2$ ternary heterojunction for efficient visible-light acetaminophen degradation: Enhanced oriented charge migration

Acetaminophen (ACE), a representative emerging contaminant, is challenging to completely degrade and
detoxify due to the formation of highly toxic intermediates. Even with advanced binary heterojunction photo-
catalysts, their performance remains restricted by structural and interfacial limitations. To address these bot-
tlenecks, we rationally constructed a ternary heterojunction (MTCN-Ov), comprising two-dimensional Ti$_3$C$_2$
MXene, in-situ grown oxygen vacancy-rich TiO$_2$, and g-C$_3$N$_5$. By integrating dual Schottky junctions and an S-scheme heterojunction across multiple interfaces, we enabled directional charge migration under visible light.
Specifically, Ti$_3$C$_2$ acts as a highly conductive electron mediator, capturing photogenerated electrons from both g-C$_3$N$_5$ and TiO$_2$-Ov via their respective Schottky interfaces. In the g-C$_3$N$_5$/TiO$_2$-Ov domain, in-situ XPS confirmed the formation of an S-scheme heterojunction, which facilitates the recombination of low redox potential carriers while selectively preserving high-energy electrons and holes for redox reactions. These synergistic charge dynamics, driven by built-in electric fields and the bridging effect of Ti$_3$C$_2$, establish a continuous atomic-scale electron transfer network. ... mehrAs a result, the MTCN-Ov system enables highly efficient and directional electron transfer to ACE molecules and significantly enhances the generation of •OH and •O$_2$$^-$. Under visible-light irradiation, ACE was completely degraded within 45 min, while the formation of toxic intermediates was effectively suppressed. This study demonstrates the great potential of MTCN-Ov for selective and efficient removal of pharmaceutical contaminants in aquatic environment.