Conjugated CdS/CNTs/ZnxAg1−xWO4 S-scheme heterostructure for enhanced photocatalytic degradation of antibiotics: Targeting photogenic charge separation and transmission

Abstract

Manipulating charge transfer at the nanostructure interface of a S–scheme heterostructure is critical to the photocatalytic performance and practical application. Here, we design a novel S–scheme conjugated photocatalyst CdS/CNTs/ZnxAg1−xWO4 (CZA/CNx) capable of accelerating antibiotic degradation under visible light. Experimental results showed that first-order kinetic constants of CZA/CNx were 1.59, 2.57, and 1.73 times that of CdS/ZnxAg1−xWO4 for amoxicillin degradation, respectively. A series of characterization analysis demonstrated that delocalized π-bonds were existed in a whole composite system (SC–CC···CO) and its could produce a easily excited state of triplet state T1 instead of lowest singlet excited state S1 generated from the ground state (S0). In situ XPS indicated that the electrons will migrate from CdS to ZA/CNx via conjugated redox pathway. Furthermore, this pathway of charge transfer is prevented from the opposite trend, which is depended on establishment of internal electric field and a Schottky barrier in S–scheme conjugated photocatalyst. The density functional theory calculation (DFT) revealed Fermi level of CdS and ZAx were −3.81 eV and −6.80 eV, indicating the conjugated redox pathway of electron transfer is feasible. The successful application of this S–scheme conjugated photocatalyst strategy provide a new direction of conjugated photocatalyst synthesis to address the increasing antibiotic contamination.