Mesoporous\nAtomically Dispersed Fe Catalysts with\nEnhanced Nonradical Pathways in Fenton-like Reactions: The Role of\nSiO<sub>2</sub> Templates

Single-atom catalysts (SACs) are extensively applied\nin Fenton-like\ncatalytic processes to treat water pollutants. However, the role of\nthe porous structures of SACs supports in catalytic reactions is often\noverlooked despite its significant contribution to mass diffusion\nduring the reaction. Herein, we adopted a hard-template-assisted approach\nto fabricate Fe-based SACs (Fe-SACs) featuring a mesoporous architecture.\nThe SiO<sub>2</sub> template not only adjusts the pore architecture\nof the support but also facilitates the conversion of active sites\nfrom nanoscale sites to single-atom sites, thereby improving the selectivity\nfor pollutant degradation via nonradical pathways (singlet oxygen\nand electron transfer mechanism). The experimental results demonstrated\nthat using large-sized SiO<sub>2</sub> (∼200 nm) as a template\nleads to metal aggregation on its surface, forming Fe nanoparticles\n(Fe-NPs). Fe-NPs exhibit narrow pore structures that prevent peroxymonosulfate\n(PMS) from being activated, resulting in a slow degradation of pollutants\nprimarily through radical pathways. In contrast, employing small-sized\nSiO<sub>2</sub> (∼10 nm) as a hard template not only produces\nsupports with mesoporous structures but also promotes the building\nof single-atom active sites. The prepared Fe-SACs effectively activated\nPMS through nonradical pathways and removed contaminants at a rate <i>k</i> of 0.89 min<sup>–1</sup>, 33 times faster than\nFe-NPs. This template-assisted method sheds light on the synthesis\nof effective Fenton-like catalysts with porous structures that enhance\nthe efficient breakdown of contaminants in wastewater.