Asymmetry Spin-Orbit of Single Iron Active Site Enhance Oxygen Reduction Reaction.

Asymmetric electron distribution of single-atom catalysts (SAC) is an important means of regulating intrinsic catalytic activity. However, limited by synthetic preparation methods, understanding of the mechanism of asymmetrically coordinated single-atom catalysis is restricted. In this study, leveraging the micropore confinement effect, nitrogen and phosphorus-doped microporous carbon is used as a substrate to successfully anchor singly dispersed Fe atoms, constructing the asymmetrically coordinated single-atom Fe site coordinated with N and P atoms (Fe-SAs/NPC). The existence of the Fe-NP site structure breaks the symmetry Fe-N in Fe-SAs/NC, which would optimize the adsorption strength of intermediates. The resulting Fe-SAs/NPC exhibits excellent ORR activity with a half-wave potential of 0.91 V (0.1 m KOH), which is 40 mV higher than that of Fe-SAs/NC (0.87 V). Combined with theoretical calculations, an in-depth understanding of the asymmetric electronic configuration from the perspective of spin orbitals can enhance the electronic activity near the Fermi level and strengthen the adsorption of oxygen-containing intermediates. This work provides new perspectives and ideas for understanding spin-electronic behavior in catalytic processes. Furthermore, the Zn-air battery constructed using Fe-SAs/NPC exhibits a high power density of 187.7 mW cm and a specific capacity of 819.6 mAh g at 10 mA cm.