Construction of 0D/2D/0D (001)TiO2/Ti3C2/ZnTCPP S-scheme heterojunction with robust built-in electric field for boosting visible-light-driven tetracycline degradation and hydrogen evolution activity

The development of efficient S-scheme heterojunctions was crucial for addressing the limitations of insufficient light absorption and rapid charge recombination in photocatalysis. In this study, a dual-synergistic 0D/2D/0D (001)TiO 2 /Ti 3 C 2 /ZnTCPP S-scheme heterojunction was rationally designed. The matched energy levels between (001)TiO 2 and ZnTCPP metalloporphyrin drove the formation of a robust built-in electric field, serving as the endogenous S-scheme charge separation core that preserved strong redox capacity. Meanwhile, the metallic Ti 3 C 2 MXene acted as an exogenous high-conductivity transport bridge, accelerating directional carrier migration to surface active sites. The composite was successfully fabricated via a hydrothermal method combined with electrostatic self-assembly. Comprehensive characterization by XRD, TEM, and XPS confirmed that (001)TiO 2 nanoparticles and amorphous ZnTCPP were uniformly anchored onto Ti 3 C 2 nanosheets, forming intimate 0D/2D/0D interfacial contacts with strong electronic interactions. The incorporation of ZnTCPP significantly extended the optical absorption into the visible region, while Ti 3 C 2 functioned as an efficient electron mediator and photothermal agent, further boosting reaction kinetics. Under visible-light irradiation, the optimized TTZ-2 composite exhibited exceptional dual-functional performance: a tetracycline degradation rate of 93.4% and a hydrogen evolution rate of 590.2 μmol·g −1 ·h −1 . Mechanistic investigations, supported by Kelvin probe force microscopy (KPFM) and density functional theory (DFT) calculations, revealed that the dual synergy between the endogenous built-in electric field and the exogenous Ti 3 C 2 channel synergistically facilitated the directional migration of photogenerated carriers along the S-scheme pathway, effectively suppressing recombination while preserving strong redox capabilities. This work demonstrated a viable strategy for designing multifunctional MXene-based photocatalysts for environmental remediation and solar energy conversion.