Two-step construction of WO3@TiO2/CS-biochar S-scheme heterojunction and its synergic adsorption/photocatalytic removal performance for organic dye and antibiotic

The development of visible-light-driven photocatalysts for environmental remediation is a major challenge for photocatalytic technology. Herein, a novel ternary WO3@TiO2/CS-biochar step-scheme (S-scheme) heterojunction was constructed via a two-step strategy and comprehensively characterized. The photocatalytic performance was assessed by degradation of organic dye methylene blue (MB) and antibiotic tetracycline (TC) aqueous solution under visible-light irradiation. The as-prepared WO3@TiO2/CS-biochar photocatalysts exhibited enhanced synergic adsorption/photocatalytic removal performance for MB and TC. Particularly, the WO3@TiO2/CS-biochar (20 wt%) sample possessed the optimal photocatalytic activity, which could almost completely eliminate MB and TC in aqueous solution within 2 h. The enhancement of photocatalytic activity was mainly attributed to the formation of S-scheme heterojunction between TiO2 and WO3 under the action of CS-biochar as electron transport channels and photosensitizer. Furthermore, a biochar bridging semiconductor/semiconductor S-scheme heterojunction photodegradation mechanism was speculated based on the active species trapping experiment, electron paramagnetic resonance (ESR) and photoelectrical property tests combined with the results of photocatalytic performance. The present work offers new enlightens for the preparation of biochar-bridged visible-light-driven heterojunction or composite photocatalysts.