Amorphous cobalt sulphide introduced atomic H*/H+ for H2O2 electrosynthesis and enhanced Fe(II) regeneration in electro-Fenton process at macroneutral pH

Cathode materials with high hydrogen peroxide (H 2 O 2 ) selectivity and Fe 2+ regeneration under macroneutral conditions are the essential for practical electro-Fenton processes. Herein, we develop an amorphous cobalt sulphide (CoSx(t = x)@Cu) cocatalytic electro-Fenton (EF) system capable of effectively degrading organic pollutants, such as sulfamethoxazole, at macroneutral pH conditions. Owing to the flexible electronic properties of amorphous structures and charge redistribution triggered by S defects, the optimum CoSx(t = 8)@Cu cathode successfully introduces H*/H + and promotes the in-situ evolution of H 2 O 2 . Additionally, an acidic microenvironment was constructed on the CoSx(t = 8)@Cu surface by the unreduced H*/H + , enabling a self-adjustment from alkalinity to acidity in the EF reaction without adding acid. Such self-adjustment effectually inhibits iron sludge production and promotes Fe 2+ regeneration, assuring 80% Fe 2+ cycling efficiency. More importantly, the EF system possesses outstanding stability and applicability for organic pollutant remediation regardless of water matrices. This work elucidates the intrinsic mechanism of amorphous electrocatalysts in overcoming the pH limitation of EF reactions, extending the applicability of Fenton technology.