Harnessing Z-scheme heterojunction synergy in B4C decorated with nano TiO2 for solar-driven degradation of biocidal pollutants

Conventional type-II heterojunctions broaden visible-light absorption and enhance charge separation but weaken redox potentials via charge migration, reducing thermodynamic driving force for surface catalysis. A novel direct Z -scheme heterojunction photocatalyst was constructed by decorating B 4 C with TiO 2 nanoparticles for efficient solar-driven degradation of 1,2-benzisothiazolin-3-one and other biocidal pollutants. The optimized TiO 2 /B 4 C photocatalyst achieved 98% BIT degradation within 4 h under simulated solar irradiation, with an apparent rate constant of 1.00 h −1 , approximately 38 and 6.2 times higher than those of pristine B 4 C and TiO 2 , respectively. The incorporation of B 4 C broadened visible-light absorption and promoted interfacial charge separation, while the formation of an internal electric field enabled a direct Z -scheme charge-transfer pathway that preserved strong redox potentials. As a result, photogenerated electrons accumulated on B 4 C and generated O 2 •− radicals, whereas holes retained on TiO 2 produced • OH radicals, jointly driving the oxidative degradation of pollutants. Electron Spin Resonance and radical scavenger analyses confirmed O 2 •− and • OH as the key reactive species. Density functional theory (DFT) calculations further elucidated the interfacial charge-transfer mechanism and the degradation pathway of BIT. This work demonstrates that the TiO 2 /B 4 C Z -scheme heterojunction provides an efficient strategy for solar-driven photocatalytic removal of biocidal pollutants, providing insights into rational design of high-performance photocatalysts for environmental remediation.