One-pot construction of unprecedented direct Z-scheme ZnS/GaOOH heterojunction for photodegradation of antibiotics

An unprecedented ZnS/GaOOH heterojunction structure is prepared through one-pot hydrothermal process to improve the charge separation for photocatalysis. The photocatalytic performance of the ZnS/GaOOH heterojunction photocatalyst is investigated by degrading antibiotics under ultraviolet light. The results show that the matchable ZnS/GaOOH presents optimal photocatalytic performance and can remove 86.4% of tetracycline (TC) in 150 min, which is higher than that of pure ZnS (60.4%) and pure GaOOH (61.9%). The ZnS/GaOOH can also remove ciprofloxacin (CIP), Levofloxacin (LF) and rhodamine B (RhB) effectively. In addition, ZnS/GaOOH heterojunction almost maintains its photocatalytic degradation activity of RhB at the initial level after 3th cycles. The morphologies, structures and optical properties of the photocatalysts are comprehensively characterized. The results show that the heterojunctions are formed by ZnS spheres attaching on GaOOH rods gradually with hydrothermal time increasing. However, when hydrothermal time excess to 3 h, oversize ZnS spheres will lead heterojunctions unmatchable. The optical and electrical properties characterizations reveal that the superior photodegradation activities for both TC and RhB of GaZn-3 to other GaZn-n and pure ZnS, GaOOH are ascribed to the efficient charge separation in matchable ZnS/GaOOH heterojunction. The photodeposition experiments and electron spin-resonance (ESR) results disclose ZnS/GaOOH heterojunction provides a direct Z-scheme mechanism of charge path for more efficient redox capacities. And the effective formation of .O2- and .OH together with photogenerated e- and h+ improve the degradation activity. This work provides an effective route to regulate a matchable and stable heterojunction, and will provoke the rational fabrication of direct Z-scheme mechanism heterojunction photocatalysts.