FeCo-Doped Hollow Bamboo-Like C-N Composites as Cathodic Catalysts for Zinc-Air Battery in Neutral Media

Precious metal-free C-N composites possess great significance as replacements for Pt-based catalysts used as cathodes in fuel cells. Herein, we have fabricated the Fe/Co-doped C-N composite catalysts, marked as C-N, Co/C-N and Fe-Co/C-N, by direct pyrolysis of the dried suspensions consisting of cobalt/iron salt, dicyandiamide and glucose. For the Fe-Co/C-N catalyst, its morphological texture is characterized by Fe-Co nanoparticles and hollow bamboo-like nitrogen-doped carbon nanotubes (C-N nanotubes). The electroactivity of the prepared samples for oxygen reduction reaction (ORR) in a neutral medium has been investigated. The catalyst Fe-Co/C-N presents the highest ORR current density of 5.1 mA·cm−2 @0.8V (vs Ag/AgCl) in a neutral medium. A zinc-air battery in neutral KNO3 solution, assembled with zinc as the anode and carbon paper loaded by the prepared catalysts as the air electrode (cathode), displays excellent and stable discharge performance. The maximum power density of the Fe-Co/C-N catalyst is 32 mW·cm−2, and the continuous discharge time reaches 209, 155, 17 h at constant discharging current density of 25, 50 and 100 mA·cm−2 respectively. Simultaneously, the air electrode using the Fe-Co/C-N as the catalyst shows good cycle stability and repeatability. Results reveal that the Fe-Co/C-N is a very promising cathodic catalyst applied in neutral zinc-air battery.