Single-Atom Fe Catalysts for Fenton-Like Reactions: Roles of Different N Species.

Recognizing and controlling the structure-activity relationships of single-atom catalysts (SACs) is vital for manipulating their catalytic properties for various practical applications. Herein, Fe SACs supported on nitrogen-doped carbon (SA-Fe/CN) are reported, which show high catalytic reactivity (97% degradation of bisphenol A in only 5 min), high stability (80% of reactivity maintained after five runs), and wide pH suitability (working pH range 3-11) toward Fenton-like reactions. The roles of different N species in these reactions are further explored, both experimentally and theoretically. It is discovered that graphitic N is an adsorptive site for the target molecule, pyrrolic N coordinates with Fe(III) and plays a dominant role in the reaction, and pyridinic N, coordinated with Fe(II), is only a minor contributor to the reactivity of SA-Fe/CN. Density functional theory (DFT) calculations reveal that a lower d-band center location of pyrrolic-type Fe sites leads to the easy generation of Fe-oxo intermediates, and thus, excellent catalytic properties.