Synergy of oxygen vacancies, Lewis acid sites, and interfacial chemical bonds on ZnSnO3/AgI for photodegradation of tetracycline

Chemically bonded Z-scheme ZnSnO3/AgI composites rich in oxygen vacancies (OVs) and Lewis acid sites were prepared successfully and showed excellent photocatalytic activities. Especially, ZnAg-2 degraded 96.1% tetracycline under visible light irradiation for 15 min. OVs contributed to Lewis acid sites production and interfacial chemical bonds formation through weakening the metal-O bonding. Lewis acid sites favored the adsorption of electron-rich tetracycline. Interfacial chemical bonds together with Z-scheme structure accelerated electron transfer and retained the high redox ability of ZnSnO3 and AgI. OVs contributed to singlet oxygen (1O2) production through facilitating the energy transfer from triplet exciton to O2. ZnSnO3/AgI composites possess good reusability and show great practical application potential. Based on ROSs generation and photoreduction experiment, the photocatalytic mechanism of the ZnAg composites was proposed. The possible degradation pathway was deduced and the biological toxicity was evaluated based on detected degradation intermediates. This work highlights the significant roles of OVs, Lewis acid sites, and chemical bonding in improving the photocatalytic activity of Z-scheme composites and provides new insight into designing high efficient photocatalysts.