A bifunctional single-atom catalyst assisted by Fe2O3 for efficiently electrocatalytic perfluorooctanoic acid degradation by integrating reductive and oxidative processes

Abstract

Concerns about the environmentally persistent and bioaccumulative per/polyfluoroalkyl substances (PFAS) in water are emerging since their potentially harmful effects on humans. However, the rapid mineralization and defluorination of PFAS are rarely achieved although various techniques have been developed. Hereby, a bifunctional single-atom catalyst (SAC) characterizing a Co-CN2 configuration is constructed, which can simultaneously induce the degradation of PFOA and reduce O2 to H2O2. Oxidative and reductive degradation are intergraded within one system for perfluorooctanoic acid (PFOA) degradation with the immobilized Fe2O3 as a Fenton catalyst. Consequently, 96.1% of PFOA is degraded over Co-CN2-Fe2O3 at −0.06 V in an H-cell equipped with a gas diffusion cathode. The defluorination efficiency reaches 95.9% in 120 min. The Co site shielding experiment combined with the ·OH quench experiment validates that both reductive and oxidative degradation processes are indispensable in rapid and complete PFOA mannerization and defluorination. A reduction and oxidation cooperative chain shortening mechanism is proposed for PFOA degradation based on the intermediates analysis and shielding experiment.