Differential catalytic mechanism induced by selective adsorption of pollutants in metal clusters decorated single atom catalyst mediated heterogeneous Fenton-like reaction

Although metal clusters are generally considered as impurities accompanying the synthesis of single atom catalysts, their extraordinary potential in regulating single atom catalytic reactions has attracted widespread attention. In this study, iron cluster decorated single atom iron catalyst (Fe-SACAs) were synthesized to activate peroxymonosulfate (PMS) for the removal of organic pollutants, and a differential PMS activation mechanism induced by selective adsorption of pollutants was observed for the first time. The chemical coordination between pollutants and active sites was identified as the dominant chemisorption mechanism for the adsorption of organic pollutants by Fe-SACAs. The competitive occupation of PMS activation sites by pollutants induced by the diversity of targeted pollutant molecules in ionization potentials was thereby revealed to be the inducement for the adsorption-dependent oxidation. The adsorption-dependent oxidation mechanism was fully elucidated using density functional theory (DFT). Finally, an optimized treatment process was proposed based on the adsorption-dependent oxidation mechanism, which achieved zero oxidant residue and pollutant emission simultaneously. This study unveils the crucial effect of reactant mass transfer and adsorption on the oxidation process in Fe-SACAs mediated Fenton-like reactions.