Facile defect engineering in ZnIn2S4 coupled with carbon dots for rapid diclofenac degradation

Abstract Semiconductor-mediated photocatalysis is a promising photochemical process for harvesting inexhaustible solar energy to address the energy crisis and environmental issues. However, the low solar-light response and poor carrier migration are severe drawbacks that limit its practical application. Herein, we propose a convenient pathway for improving electron-hole separation and solar energy utilisation by engineering defective ZnIn2S4 with doping of carbon dots. The optimum ZnIn2S4/CD200 nanosheet exhibited 100% diclofenac (DCF) degradation within 12 min under visible-light. The estimated photocatalytic efficiency under natural sunlight was 98.2%. Scavenging experiments and electron spin resonance (ESR) analysis indicated that the superoxide radical (O2•−), photoelectron (e−), hole (h+) and hydroxyl radical (•OH) were the predominant contributions in the ZnIn2S4/CD200/DCF/visible light system. Furthermore, ZnIn2S4/CD200 exhibited excellent reusability and stability after 4 times recycling. The photodegradation routes mainly involved hydroxylation, decarboxylation, C-N bond cleavage, dechlorination, ring closure, and ring-opening. The ecological risk assessment and total organic carbon (TOC) tests exhibited desirable toxicity reduction and mineralization results. These observations not only offer a facile strategy for the construction of defective ZnIn2S4, but also pioneer the direct utilisation of natural light for highly efficient environmental remediation.