Synergistic effects for boosted persulfate activation in a designed Fe–Cu dual-atom site catalyst

Abstract

Advanced oxidation processes (AOPs) are promising ways for oxidative degradation of organic pollutants. Atom-dispersed transition metal–nitrogen–carbon (M–N–C) materials exhibit excellent efficiency in activating peroxide bonds and have been extensively pursued for environmental remediation. However, M–N–C with single atoms suffer from intrinsic performance limit of complicated catalytic reactions due to structural simplicity and lack of synergistic active sites. Herein, derived from Fe/Cu–coordinated zeolitic imidazolate frameworks with molecular-scale cages, a well–designed catalyst featuring Fe–Cu dual–metal sites coordinated with N–doped carbon (Fe/Cu–N–C) was fabricated. Compared to the single-atom iron catalyst (Fe–N–C), Fe/Cu–N–C significantly enhanced the chloramphenicol removal rate from 0.073 to 0.093 min−1 due to the synergistic effects of Fe–Cu dual active site. Furthermore, Fe/Cu–N–C exhibits fantastic reactivity for peroxydisulfate (PDS) activation in a wide pH range (3.1 – 10.3). Density functional theory calculations revealed that Fe/Cu–N is the major active site, where electrons transfer from Cu to Fe ensure the low-valence state of Fe for catalytic oxidation. Besides, the optimization of adjacent Cu–N sites improves the bonding orbital distribution of Fe 3d orbitals and promotes the adsorption and cracking of PDS. These findings reveal the cooperative mechanism of Fe–Cu dual–atom site on PDS activation and develop a promising platform toward environmental purification.