Boosting peroxymonosulfate activation by porous single-atom catalysts with FeN₄O₁ configuration for efficient organic pollutants degradation

The construction of single Fe atoms with favorable electron structures is highly desired to boost peroxymonosulfate (PMS) activation for organics degradation. Herein, this study embedded isolated Fe atoms on N, O co-doped porous carbon substrate (Fe-SA-N/O-C), and first found the constructed FeN4O1 configuration can realize efficient PMS activation via electron transfer by inner-sphere complexation, instead of the usual reactive oxygen species (ROS) as a major role. Structural investigation showed that the FeN4O1 moieties possess high content of high spin (HS) Fe(II), resulting in the delocalization of unpaired electrons around Fe centers, which is benefit to transfer electrons when reacted with PMS. EIS and LSV curves further certified the electron transfer process. Density functional theory (DFT) calculations unveiled that the FeN4O1 configuration can directly adsorb O-O bond of PMS, leading to electron accumulation around Fe-O-2 bond, and then ulteriorly trigger the electron shuttling in organics degradation. Consequently, the optimized Fe-sA-N/O-C/PMS system exhibited superior oxidation ability for various organic pollutants, and was not affected by initial pH variation (3.19 similar to 10.89), inorganic anions (ClO4-, Cl- and H2PO4-) and natural organic matter (NOM) interference. Importantly, the developed system presented certain applicability in the treatment of actual water from Taihu Lake basin, China. Hence, this study not only elucidates the inner-sphere complexation-oriented electron transfer mechanism between unique FeN4O1 configuration and PMS, but provides new insights into engineered single atom catalysts for wastewater purification.