Understanding of interfacial molecular interactions and inner-sphere reaction mechanism in heterogeneous Fenton-like catalysis on Mn-N4 site

This study investigated interface molecular interactions between atomically-dispersed active sites and reactants in Fenton-like catalysis for deep understanding catalytic mechanism and dynamics. N-doped carbon nanotubes (NCNTs), atomically-dispersed Mn onto NCNTs (Mnsa-NCNT) and peroxymonosulfate (PMS) were applied as the research platforms. PMS adsorption on atomically-dispersed Mn sites was found to perform an inner-sphere interaction rather than an outer-sphere interaction on NCNT. The inner-sphere interaction leads to efficient electron transfer and robust PMS adsorption in the presence of organic pollutants, therefore high decontamination efficiency in Fenton-like catalysis. Theoretical calculation, X-ray electron spectrum, X-ray absorption spectrum indicated chemical bonds, specifically ionic bonds, were formed between Mn-N4 moieties and PMS. In contrast, the N-doped surface adsorbed PMS via van der Waals interactions. These findings provide a deep understanding of solid/liquid interface processes and additionally gives a new perspective on the superiority of single atom catalysts.