Promoting oxygen reduction via crafting bridge-bonded oxygen ligands on a single-atom iron catalyst

Single-atom Fe-N-C materials with Fe-N-4 coordination structures, hailed as promising catalysts, are prohibited by the severe aggregation and migration of metal atoms. Although bonding-confinement strategies can be used to effectively regulate and strengthen the coordination of isolated metal atoms, the precise control of the coordination environment of metal centers remains a challenge. Herein, we report a rational strategy by which to bond iron phthalocyanine (FePc) on pre-synthesized Fe-N-C materials to further obtain anatomically dispersed Fe-N-4 catalysts. The axial coordination of O-FeN4 sites to form a Fe-O-Fe bridge bond lowers the overpotential for the oxygen reduction reaction (ORR). Incorporation of the O atom stimulates the adsorbed O-2 to obtain more electrons, thereby enhancing the adsorption and activation of O-2. The catalyst demonstrates a half-wave potential of 0.866 V (versus RHE) and kinetic current density of 11.49 mA cm(-2), significantly outperforming commercial Pt/C. The primary Zn-air battery assembled with such a catalyst exhibits a high current density of 136 mA cm(-2) @ 1.0 V and a maximum power density of 205 mW cm(-2), supporting its potential feasibility in practical applications. Our findings provide a new avenue for tuning the coordination environment of single-atom catalysts to enhance their ORR activity.

Automated summary

This study presents a rational strategy to obtain anatomically dispersed Fe-N-4 catalysts by bonding iron phthalocyanine (FePc) on pre-synthesized Fe-N-C materials. The formation of Fe-O-Fe bridge bonds lowers the overpotential for the oxygen reduction reaction (ORR). The introduction of O atom stimulates the adsorption and activation of O2, resulting in improved ORR activity. The catalyst exhibits higher performance than commercial Pt/C catalyst.