Axial nitrogen-coordination engineering over Fe-Nx active species for enhancing Fenton-like reaction performance

Abstract

Activating hydrogen peroxide (H2O2) to produce hydroxyl radical (•OH) (Fenton-like process) is of great importance in heterogeneous catalytic oxidations. However, most of transition metal nano-catalysts as well as recently reported carbon supported Fe-N4 single atom catalysts (SACs) suffer from unsatisfactory catalytic performance. Herein, a novel Fe1/C3N4 SAC with Fe-N5 active site was constructed. Using this SAC, the electron/structure-symmetry of Fe-N4 site can be broken by axial nitrogen-coordination, which transforms less active Fe-N4 species into highly active Fe-N5 species in Fenton-like reaction. Specifically, Fe-N5 site exhibits an unprecedented activity for 3,3′,5,5′-tetramethylbenzidine oxidation, which is at least one order of magnitude more active than reported Fe-N4/C SACs. Mechanism studies reveal that the unique role of axial nitrogen-coordination over Fe-Nx sites is to change the adsorption behavior of H2O over Fe-N5 site without influencing H2O2 activation. This discovery provides a new approach for rationally designing efficient catalysts in Fenton-like reactions.