Molten‐Salt Media Synthesis of N‐Doped Carbon Tubes Containing Encapsulated Co Nanoparticles as a Bifunctional Air Cathode for Zinc‐Air Batteries

Cost efficient bifunctional air cathodes possessing high electrocatalytic activity are of great importance for the development of secondary Zn‐air batteries. In this work, cobalt nanoparticles are encapsulated within a 3D N‐doped open network of carbon tubes (Co@N‐CNTs) by a molten‐salt synthesis procedure conducted at a high temperature. Physical characterization demonstrates that Co@N‐CNTs are comprised of Co particle inserted carbon tubes with mesoporous tube walls, providing significant active surface area for electrochemical reactions. High electrocatalytic activity of Co@N‐CNTs towards both oxygen evolution and oxygen reduction reactions is due to its well‐developed active surface and a synergistic effect between N‐doped carbon and Co nanoparticles. Both primary and secondary Zn‐air battery cells assembled using Co@N‐CNTs as an air cathode show higher electrochemical performance than similar cells containing commercial Pt/C and Pt/C +RuO 2 , making the newly developed material a promising alternative to existing metal‐based air cathodes.