Nonmetal Doping Modulates Fe Single-Atom Catalysts for Enhancement in Peroxidase Mimicking via Symmetry Disruption, Distortion, and Charge Transfer.

Developing biomimetic catalysts with excellent peroxidase (POD)-like activity has been a long-standing goal for researchers. Doping nonmetallic atoms with different electronegativity to boost the POD-like activity of Fe-N-C single-atom catalysts (SACs) has been successfully realized. However, the introduction of heteroatoms to regulate the coordination environment of the central Fe atom and thus influence the activation of the HO molecule in the POD-like reaction has not been extensively explored. Herein, the effect of different doping sites and numbers of heteroatoms (P, S, B, and N) on the adsorption and activation of HO molecules of Fe-N sites is thoroughly investigated by density functional theory (DFT) calculations. In general, alternation in the catalytic efficiency directly depends on the transfer of electrons and the geometrical shifts near the Fe-N site. First, the symmetry disruption of the Fe-N site by P, S, and B doping is beneficial to the activation of HO due to a significant reduction in the adsorption energies. In some cases, without Fe-N site disruption, the configurations fail to modulate the adsorption behavior of HO. Second, Fe-N-P/S configurations exhibit a stronger affinity for HO molecules due to the significant out-of-plane distortions induced by larger atomic radii of P and S. Moreover, the synergistic effects of Fe and doping atoms P, S, and B with weaker electronegativity than that of N atoms promote electron donation to generated oxygen-containing intermediates, thus facilitating subsequent electron transfer with other substrates. This work demonstrates the critical role of tuning the coordinating environment of Fe-N active centers by heteroatom doping and provides theoretical guidance for controlling the types by breaking the symmetry of SACs to achieve optimal POD-like catalytic activity and selectivity.