Elucidating diatomic catalysis for contaminants degradation: Role of multi-functional Fe/Co sites in peroxydisulfate activation

The application of catalysts with highly available active sites, such as single-atom catalysts (SACs), is a growing trend in peroxysulfate activation for organic contaminant degradation. However, the single functional active site of SACs limits its performance in such reactions involving multiple steps or reactants. For this issue, a Fe-Co diatomic catalyst (FeCo-N-C) with multi-functional active sites is synthesized to abate bisphenol A (BPA) using peroxydisulfate (PDS) as an oxidant. X-ray Absorption Fine Structure (XAFS) measurement confirms the successful construction of diatomic Fe-N4/Co-N4 sites. The FeCo-N-C exhibits a higher normalized reaction rate (2.07 × 105 min−1 mol−1) in BPA removal than previously reported SACs. Low-temperature electron paramagnetic resonance analysis reveals that Fe-N4 and Co-N4 process different intrinsic properties (spin states), which may lead to their diverse functions in the PDS activation process. The Co sites can significantly accelerate electron transfer and enhance the PDS adsorption abilities. As a complement, Fe sites perform better in the electrostatic interaction and destabilization of PDS. This study not only explains the synergy of multi-functional diatomic sites from the whole PDS activation process but provides a reliable reference for the elimination of emerging organic contaminants.