Boosting Oxygen Reduction Reaction Performance of Fe Single-Atom Catalysts Via Precise Control of the Coordination Environment

Fe single-atom on N-doped carbon (FeN-C) catalysts emerge as promising alternatives to commercial Pt/C for the oxygen reduction reaction. Heterogeneous atom doping is proposed to be effective for modulating catalyst performance. Despite this, the relationship between the fine coordination structure of the doped atoms and catalytic activity of the central metal site remains poorly understood. Herein, Fe single-atom catalysts with S doped in either the first coordination shell (FeSN-C) or the second coordination shell (FeN-SC) of the Fe active site are synthesized to compare the effects of different coordination structure. FeN-SC exhibits prominent performance with a half-wave potential of 0.92 V in rotating disk electrode and a peak power density of 251 mW cm(-2) in the zinc-air battery. Theoretical studies reveal that S doping effectively modulates the electronic structure and charge transfer at the Fe center. Compared to S atoms directly coordinated within the first coordination shell, S located in the second coordination shell is more effective in optimizing the adsorption and desorption energy barriers of oxygen-containing intermediates at the active sites. This study provides a new strategy to adjust the catalytic performance by engineering the multilayer coordination structure at the active center of the single-atom catalyst.