Bio-inspired engineering of a dual sulfur vacancy-engineered S_V-Bi₂S₃/S_V-ZnIn₂S₄ Z-scheme heterojunction for boosted photodegradation of chloroquine phosphate

The construction of heterojunction photocatalysts containing atomic vacancies can effectively increase the number of adsorption sites and lowered the energy barrier of key intermediates. Herein, A series of S_V-Bi₂S₃/S_V-ZnIn₂S₄ heterojunctions were successfully designed and fabricated by solvothermal method with bio-inspired engineering. Moreover, the optimal system (S_V-BZIS-50 composites) degraded 99.3% of chloroquine phosphate (CQ) and displayed high oxidation ability (>76.5%) for different types of antibiotics (SMZ, CIP, AMX, BPA, TC) within 60 min. and the tightly coupled interface formed a built-in electric field with double sulfur vacancies. Compared with the Bi₂S₃/ZnIn₂S₄ heterojunction, the introduction of sulfur vacancies into S_V-Bi₂S₃/S_V-ZnIn₂S₄ can regulate the adsorption energy between the active site and the intermediate through the size effect, achieving enhanced photocatalytic efficiency. DFT calculations and experimental results confirmed that sulfur vacancies not only improve the interfacial microenvironment to enhance the adsorption capacity and activation ability of the CQ, but also to lower the energy barrier for the generation of O₂-derived *OOH intermediates. More importantly, the Bi[sbnd]N bonds and Zn[sbnd]N bonds formed between S_V-BZIS-50 and the N atoms in CQ molecules serve as atomic interfacial electronic bridges. This facilitates the migration of photogenerated charges between S_V-ZnIn₂S₄ and S_V-Bi₂S₃, thereby significantly enhancing the charge transfer efficiency of the Z-scheme heterojunction. Additionally, the photocatalytic mechanism of Z-scheme heterojunction has been investigated using XPS, DFT, EPR and photoelectrochemical tests. Overall, these findings provide new insights to advance vacancy engineering and interfacial modulation in the application of photocatalytic heterojunctions.