The key to prolong the life of Fe-based cathode for electro-activating peroxydisulfate: Surface oxygen

Electro-activating peroxydisulfate (PDS) based on the cathode represents a highly promising advanced oxidation process; however, its longevity is constrained by cathode leaching. In this work, we demonstrate that the γ-FeOOH/Fe Foam and α-Fe₂O₃/Fe Foam obtained by engineering a protective layer containing iron and oxygen on Fe Foam exhibit significantly extended service life of 53 h and 47 h, 2.94-fold and 2.61-fold longer than that of the original Fe Foam (18 h), while showing similar pseudo-first-order kinetics. Structural evolution analysis and density functional theory simulations reveal that surface oxygen plays a crucial role in reducing the leaching of Fe from the cathode by immobilizing Fe ions and converting them in-situ into stable Fe₃O₄. The electro-activation mechanism of PDS on the cathode, the degradation pathways of atrazine (ATZ), and the effects of operating conditions are systematically investigated and elucidated. This work underscores the pivotal role of surface oxygen in prolonging the longevity of Fe-based cathodes, thereby contributing to the development of protective layers.