Towards High-Performance Electrocatalysts for Oxygen Reduction: Inducing Atomic-Level Reconstruction of Fe-Nx Site for Atomically Dispersed Fe/N-Doped Hierarchically Porous Carbon.

A rational and effective strategy for the synthesis of a high-performance non-precious metal electrocatalyst for oxygen reduction reaction (ORR) was developed by inducing reconstruction of Fe-Nx site on pig-bone-derived nitrogen-doped hierarchically porous carbon. The resultant Fe/N-doped carbon electrocatalyst possessed abundant atomically dispersed non-planar Fe-N4 ORR active sites, with absolute presence of active D1 (FeII -N4 ) and D3 (N-FeII -N2+2 ) sites, as well as large specific surface area and three-dimensional porous structure with hierarchical micro-/meso-/macro-pore distribution, which increased the utilization of active sites and promoted mass transport of ORR reactants. This resulted in a remarkably superior ORR activity with half-wave potential of 0.87 V (20 mV higher than Pt/C) and kinetic current density of 10.9 mA cm-2 at 0.85 V (2.3-fold of Pt/C) in alkaline electrolyte. This methodology provides a route for atomic-level design of high-performance ORR electrocatalyst.