N-, Fe-Doped carbon sphere/oriented carbon nanofiber nanocomposite with synergistically enhanced electrochemical activities

Abstract

Catalysts for the oxygen reduction reaction (ORR) are crucial in metal–air batteries, fuel cells and other electrochemical devices. Developing heteroatom-doped carbon catalysts with high performance and stability in alkaline media for practical application of metal–air batteries or in acidic media for practical application of proton exchange membrane fuel cells is still difficult and challenging. Here, we report the N-, Fe-doped carbon sphere/oriented carbon nanofiber nanocomposite (NFe-CS/CNF). N-, Fe-doped carbon spheres (NFe-CS) were derived from p-phenylenediamine and oriented N-, Fe-doped carbon nanofibers (NFe-CNF) were derived from o-phenylenediamine. 3.89 at% of N and 0.38 at% of Fe were doped in a typical product, which has high surface area. The typical product exhibits a high ORR activity and stability in acidic media and reveals superior stability and tolerance to methanol than Pt/C. In alkaline media, the typical product shows superior activity to Pt/C. The performance of a zinc–air full cell under real battery operation conditions indicates that the typical product is a competitive alternative to commercial PtC. The unique structure of NFe-CS/CNF could create strong interactions between the nanospheres and oriented nanofibers, promote charger transfer at the interface and improve the conductivity. This work provides a new fundamental understanding and design strategy for excellent carbon-based ORR catalysts.