Porous cobalt-nitrogen-doped hollow graphene spheres as a superior electrocatalyst for enhanced oxygen reduction in both alkaline and acidic solutionsElectronic supplementary information (ESI) available. See DOI: 10.1039/c5ta04852d

Porous cobalt-nitrogen-doped hollow graphene spheres were prepared by a template synthesis method. As a catalyst for the oxygen reduction reaction, they exhibit an excellent electrocatalytic activity, superior methanol tolerance and strong durability, not only in alkaline solution, but also in acidic solution. The unprecedented electrocatalytic performance of the catalyst is attributed to the well-defined morphology, high specific surface area (321 m 2 g −1 ), large pore volume (1.8 cm 3 g −1 ) and homogeneous distribution of cobalt-nitrogen active sites. Porous cobalt-nitrogen-doped hollow graphene spheres exhibit an excellent electrocatalytic performance, not only in alkaline solution, but also in acidic solution.