Development of efficient and promising bifunctional electrocatalysts for oxygen reduction and evolution reactions is desirable.Herein,cobalt nanoparticles embedded in nitrogen and sulfur co-doped carbon nanotubes (Co@NSCNT) were prepared by a facile pyrolytic treatment.The cobalt nanoparticles and codoping of nitrogen and sulfur can improve the electron donor-acceptor characteristics of the carbon nanotubes and provide more active sites for catalytic oxygen reduction and evolution reactions.The prepared Co@NSCNT,annealed at 900 ℃,showed excellent electrocatalytic performance and better durability than commercial platinum catalysts.Additionally,Co@NSCNT-900 catalysts exhibited comparable onset potentials and Tafel slopes to ruthenium oxide.Overall,Co@NSCNT showed high activity and improved durability for both oxygen evolution and reduction reactions.