Vacancy-rich NiFe-LDH/carbon paper as a novel self-supporting electrode for the electro-Fenton degradation of polyvinyl chloride microplastics

Abstract

Electrochemically upcycling polyvinyl chloride (PVC) into high-value small molecules represents a sustainable strategy for mitigating plastic pollution. Herein, a cost-effective self-supporting electrode with abundant vacancies, i.e., NiFe-layered double hydroxide nanoarrays in-situ grown on the surface of carbon paper (denoted as NiFe_V-LDH/CP), is developed for the electro-Fenton degradation of PVC microplastics (MPs). The NiFe_V-LDH catalyst shows a high selectivity of 76 % towards H₂O₂ production via two-electron oxygen reduction reaction (2e^- ORR). Density functional theory (DFT) calculations reveal that the energy barrier of rate-determining step (*H₂O₂ desorption) decreases over the vacancy-enriched NiFe_V-LDH related to the pristine NiFeZn-LDH. The influence of vacancy concentration, reaction temperature and initial concentration of PVC MPs were systematically investigated. Under optimized conditions, the NiFe_V-LDH/CP electrode exhibits an outstanding degradation performance of PVC MPs via direct cathodic reduction and oxidation by hydroxyl radicals. This work demonstrates that the electro-Fenton technology using LDH-based self-supporting electrodes is a promising and environmentally-friendly approach for waste plastic treatment.