Cobalt nanoparticles encapsulated in N-doped graphene nanoshells as an efficient cathode electrocatalyst for a mechanical rechargeable zinc–air battery

Abstract

Air-cathodes with properties of efficiency, durability and low cost are essential for high performance metal–air batteries and fuel cells for practical applications. In this study, non-precious metal ORR electrocatalysts derived by the encapsulation of Co nanoparticles in N-doped graphene nanoshells were synthesized by a typical one-step pyrolysis process. Compared with commercial Pt/C catalysts, the prepared Co-30@N-G hybrid electrocatalyst showed a high ORR activity at the same level in an alkaline medium. Subsequently, the Co-30@N-G hybrid electrocatalyst has been used as a cathode of Zn–air batteries, which displays equivalent performance to the systems derived using a commercial Pt/C catalyst. The Co-30@N-G derived mechanical rechargeable Zn–air battery showed a persistent flat discharge curve with minimum voltage loss at a high discharge rate of 40 mA cm⁻². The robustness of the Co-30@N-G ORR catalyst can allow the batteries to work constantly by periodically replacing the Zn anode and electrolyte, presenting an efficient and economical cathode for Zn–air flow batteries or Zn–air fuel cells.