Carbon nanotube-linked hollow carbon nanospheres doped with iron and nitrogen as single-atom catalysts for the oxygen reduction reaction in acidic solutions

Abstract

Non-noble metal electrocatalysts toward the oxygen reduction reaction (ORR) are highly required to substitute expensive Pt/C as the cathode of proton exchange membrane fuel cells. However, the relatively low ORR activity of Pt-free catalysts under acidic conditions is the major issue. Herein, we engineered a three-dimensional structure consisting of atomically dispersed Fe, N-doped hollow carbon nanospheres linked by carbon nanotubes as an electrocatalyst for the ORR. Benefiting from the unique structure and high-density atomic Fe-Nx sites, this new type of electrocatalyst showed an impressive ORR half-wave potential of 0.84 V and kinetic current density of 13.1 mA cm-2 at a potential of 0.8 V in acidic media, which was even better those of commercial Pt/C.