PMS activation by hollow sulfur doped multilayer carbon shell wrapped CoFe alloy: Confined adsorption and surface activation

Confined catalysis is an effective strategy to deal with the low utilization of active sites and poor cyclic stability in metal catalysts. However, the impact of confinement effect on the catalytic degradation process of organic pollutants is unclear. A hollow sulfur doped multilayer carbon shell wrapped cobalt iron alloy catalyst (CoFe@CS) is designed here to activate peroxymonosulfate (PMS) for bisphenol A (BPA) degradation. The hollow porous multilayer carbon shell provides a confined space for the rapid interface adsorption of PMS and in-situ degradation of BPA, which contribute to the superior BPA removal rate of nearly 100% within 20 min. Moreover, confinement catalysis favors the anti-interference ability to cope with changes in solution conditions like pH, organic matter, inorganic anions, etc., which favors the application in realistic wastewater. X-ray photoelectron spectroscopy (XPS) results demonstrate that the crucial Co2+ sites are regenerated by sulfur reduction, ensuring the sustainable use. Electrochemical analysis and density functional theory (DFT) calculations reveal that S doping improves the electron transfer capability and chemical reactivity of CoFe@CS, which drives direct oxidation as the dominant pathway for BPA degradation. The CoFe@CS/PMS system could efficiently mineralize BPA (up to 87.74%) and reduce residual toxicity. This work not only provides a reference for the design of efficient and stable transition metal catalysts but also offers a new insight into the confined degradation research of BPA in advanced oxidation technologies.