N-doped coralline Co₉S_8−xN_x for inducing Amitriptyline decontamination in Electro-Fenton Process: Degradation scheme Elucidation, nitrogen activating catalyst delocalized electron and enhancing 2-Electron oxygen reduction reaction mechanism investigation

Improving the recalcitrant emergent contaminant removal in electron-Fenton (EF) has been one of the focal problems. Here, a N-doped coralline Co₉S_8−xN_x catalyst was synthesized with high electronegativity and strong spin polarization for promoting the H₂O₂ generation efficiency and Amitriptyline (AMT) removal. After doping nitrogen, catalytic performance of Co₉S_8−xN_x has increased ∼10 % on AMT decay and the treatment time was shortened ∼40 min. Co₉S_8−xN_x induced 2-electron oxygen reduction reaction (ORR) mechanism has also been investigated. According to electronic structure analysis, electrons surrounding the cobalt atoms were redistributed and the π* orbitals of *O₂ were occupied asymmetrically forcing *O₂ to be of radical nature active for hydrogenation, which significantly reduced required absorption energy in the rate-determining step (RDS). This work clarifies the mediate role of N-doped activating delocalized electron of adjacent atoms on the surface of Co₉S_8−xN_x and also gives new insights into the rational design of catalyst for refractory pollutant degradation in wastewater.