Ruthenium oxide coated ordered mesoporous carbon nanofiber arrays: a highly bifunctional oxygen electrocatalyst for rechargeable Zn–air batteries

We synthesized RuO2-coated ordered mesoporous carbon nanofiber arrays (MCNAs) through a natural crab shell template, as a bifunctional catalyst for Zn–air batteries. The uniform RuO2-coating layer and ordered mesopores ensure high electrical conductivity and facilitate ion diffusion, respectively, which provide enough active sites for the ORR/OER; the macro-sized void spaces between carbon nanofibers not only play the role of a buffer in the reactions, but also facilitate oxygen transfer; the uniform RuO2-coating layer ensures catalytic activity and selectivity for catalyzing reactions (ORR and OER), especially the OER. As a result, this Zn–air battery exhibits much improved electrochemical performance, including relatively low overpotentials, long cycle life and superior rate capability.