Achieving efficient oxygen reduction on ultra-low metal-loaded electrocatalysts by constructing well-dispersed bimetallic sites and interconnected porous channels

Abstract

Developing highly efficient, stable, and earth-abundant electrocatalysts for the oxygen reduction reaction (ORR) is crucial for practical energy conversion devices, especially for fuel cells and metal–air batteries. Electrocatalysts with porous structures, effective composition and easily accessible active sites are extremely desirable in this tri-phase reaction. Herein, a three-dimensional hierarchically porous N-doped carbon nanofibers anchored with well-dispersed FeCo site (FeCo@PCNF) composite electrocatalyst is fabricated by a scalable electrospinning method followed by carbonization. The hierarchically porous architecture filled with interconnected channels and interlaced porosity provides the large surface area and rich exposed active sites of FeCo@PCNFs, hence, achieving accelerated mass transfer and improved ORR electrocatalytic ability. The electrocatalyst displays a more positive onset potential of 0.97 V_RHE (RHE: versus the reversible hydrogen electrode) and half-wave potential of 0.875 V_RHE under alkaline conditions, superior to commercial Pt/C. Moreover, FeCo@PCNFs exhibits good stability and tolerance to methanol. Impressively, when being used as an air–cathode in primary zinc–air batteries, FeCo@PCNFs presents a higher peak power density of 289.5 mW cm⁻² with excellent stability than Pt/C and most reported materials.