Efficient reduction-defluorination of perfluorooctanoic acid enabled by atomically dispersed Cu-NSC electrocatalyst in actual industrial wastewater: A direct electron transfer pathway.

Abstract

Cleavage of the C-F bond is a critical challenge in effectively controlling pollution from Per- and Polyfluoroalkyl Substances (PFAS). Herein, the Cu-NSC electrocatalyst was constructed for the efficient electrocatalytic reduction of perfluorooctanoic acid (PFOA). Multi-modal characterization has revealed a multifunctional micro-scale synergistic structure: atomically dispersed Cu sites with N0.5S2.1 coordination serve as active centers, whilst trace sub-nanometer clusters act as 'fluorine traps', exhibiting high reductive activity. Consequently, a PFOA degradation of up to 96.32% was achieved after 12 h processing of simulated wastewater in the Cu-NSC electrocatalytic reduction system. Also, a defluorination efficiency of 88.36% and a TOC reduction of 63.29% confirmed the deep mineralization-defluorination of PFOA. LC-MS comparative analyses of single/dual-pool systems and in-situ EPR spectra, collectively reveals that direct electron transfer (DET) is the dominant degradation mechanism. Further DFT calculations demonstrates that the C-F bond cleavage energy barrier at the α-CF₂ site substantially reduced by 303.79 kJ/mol. Eventually, the optimal PFOA degradation efficacy in actual industrial wastewater (initial 9.77 mg/L) was obtained at -1.5 V after 2 h electrolysis, with 91.40% degradation and exceeding 95% current efficiency. These demonstrate the system's excellent suitability for use in actual wastewater matrices. This work furnishes a novel paradigm for electrocatalyst design, which will facilitate controlling PFAS contamination in effluent from chemical industrial parks.