Defect-engineered FeSe2−x@C with porous architecture for enhanced peroxymonosulfate-based advanced oxidation processes

A novel heterogeneous and porous FeSe2−x @C-5 with abundant Se vacancies (Vse) was facilely synthesized via one-step carbonization-selenization approach from Fe-MOFs (metal-organic frameworks) and firstly applied in activating peroxymonosulfate (PMS) for iohexol (IOH) removal, exhibiting extraordinary catalytic performance with superior stability and adaptability. The roles and functions of Vse in the reaction system are deeply elucidated. Strikingly, systematic characterization and theoretical calculations revealed that Vse can modulate the surface electronic structure and accelerate Fe3+/Fe2+ cycle, leading to the strengthened binding energy and accelerated charge deliver for PMS activation. Accordingly, Iohexol (15 mg/L) can be eliminated within 30 min in FeSe2−x @C-5/PMS system, with apparent reaction rate constant (kapp) 23.7 times higher than that in FeSe2/PMS system. This study not only contributes to a tutorial guideline for designing high-performance catalysts by virtue of structural control and Vse engineering, but also extends its potential application in low-strength wastewater treatment.