Surface‐Mediated Production of Complexed •OH Radicals and FeO Species as a Mechanism for Iron Oxide Peroxidase‐Like Nanozymes
Kaiwei Wan, Bing Jiang, Ting Tan, Hui Wang, Minmin Liang
Abstract
Abstract Fe 3 O 4 nanoparticles (NPs) with intrinsic peroxidase‐like properties have attracted significant interest, although limited information is available on the definite catalytic mechanism. Here, it is shown that both complexed hydroxyl radicals (•OH) and high‐valent FeO species are attributed primarily to the peroxidase‐like catalytic activity of Fe 3 O 4 NPs under acid conditions rather than only being caused by free •OH radicals generated through the iron‐driven Fenton/Haber–Weiss reactions as previously thought. The low energy barrier of OO bond dissociation of H 2 O 2 /•OOH (0.14 eV) and the high oxidation activity of surface FeO (0 eV) due to the reduced state of Fe on the surface of Fe 3 O 4 NPs thermodynamically favor both the •OH and FeO pathways. By contrast, high‐valent FeO species are the key intermediates in the catalytic cycles of natural peroxidase enzymes. Moreover, it is demonstrated that the enzyme‐like activity of Fe 3 O 4 NPs can be rationally regulated by modulating the size, surface structure, and valence of active metal atoms in the light of this newly proposed nanozyme catalytic mechanism.