A single-atom Fe-N-C catalyst with superior Fenton-like reaction performance prepared facilely using microalgae: Key roles of oxygen and interactions between Fe-Nx and Fe/Fe compounds

A single-atom Fe-N-C catalysts (Fe-N-C) was successfully prepared through a facile synthesis route using microalgae to drive hydrogen peroxide (H2O2)-based Fenton-like reactions. The detailed characterization analyses confirmed the simultaneous presence of Fe/Fe compounds and Fe-Nx coordination sites in the optimal catalyst (Fe-N @ MBC) obtained through the pyrolysis of FeCl3·6 H2O and Chlorella vulgaris. Surprisingly, when applied in H2O2-based advanced oxidation processes (AOPs), Fe-N @ MBC demonstrated excellent proficiency for both H2O2 and O2 activation, with the contribution of the original dissolved oxygen for sulfamethoxazole removal reaching up to 47.59%. The experiment and density functional theory (DFT) calculation results indicated that the Fe/Fe compounds significantly boosted the activity of Fe-Nx by lowering the energy barrier of the reactive oxygen species formation and promoting the electron transfer between Fe-Nx and the oxidants (H2O2 and O2). These findings provide new insights into the facile synthesis, rational design, and catalytic mechanisms of Fe-N-C used in H2O2-based AOPs.