Precisely constructing pentagon trapped single-atomic iron sites in defective carbon for efficient oxygen electroreduction

Precisely controlling the local coordination structure of atomic Fe sites has been widely recognized as the key to attain highly efficient oxygen reduction reaction (ORR) catalysts for replacing Pt-based materials. Here, we use pre-synthesized pentagon-rich defective carbon (PDC) as a matrix material to realize a custom-made pentagon defect-coordinated Fe-C5 configuration via a chemical vapor deposition method. The intrinsic activity of as-prepared PDC-supported Fe single-atom catalysts (Fesac-PDC), in terms of specific kinetic current density (Jk-specific), mass activity, and turnover frequency (TOF), is valued to be several times higher than that of other N-coordinated counterparts. Density functional theory (DFT) calculations demonstrate that the excellent ORR activity of pentagon-type Fe-C5 sites originates from the optimized electronic state with more charge transfer and down-shifted d-band center. Our work gives new insight into boosting the ORR performance of atomic single-site catalysts via purposely and precisely constructing more unique defect-stabilized single atomic species.