Single-Atom iron catalyst activating peroxydisulfate for efficient organic contaminant degradation relying on electron transfer

Single-atom iron catalysts (SACs) have drawn extensive attention in advanced oxidation processes (AOPs) because of their tunable electron feature. Although single-atomic metal activation has been developed to optimize the organic contaminant oxidation and understand the associated mechanism governing persulfate-based AOPs, studies on peroxydisulfate (PDS) are rare. Herein, atomic iron was anchored in Enteromorpha-derived carbon matrices via a novel and cost-effective route in this work. This single atomic catalyst (FeSA-NEPBC) exhibited very high activity in PDS conversion for organic pollutant oxidation. Integrated with radical quenching experiments and electron spin resonance (ESR), the nonradical pathways of pollutant degradation was unveiled to be an electron-transfer process. Electrochemical analysis, masking experiments and theoretical calculations unraveled that FeSA-NEPBC/PDS* complex and Fe-pyridinic N4 moiety were the predominant oxidizing intermediate and active sites, respectively. The innovative application of galvanic oxidation process (GOP) was also employed to probe the mechanism. Bisphenol S (BPS) was degraded only when the catalyst-coating the graphite sheets was applied in the GOP, further confirming the occurrence of electron transfer. Moreover, the FeSA-NEPBC/PDS system exhibited favorable performance in realistic wastewater remediation scenarios. This work offers a better mechanistic understanding of PDS activation by the single-atom catalysts, while providing keen insights into the design of stable atomic metal catalysts for practical use.