A metal-organic framework devised Co-N doped carbon microsphere/nanofiber hybrid as a free-standing 3D oxygen catalyst.

A Co-N doped 3D carbon microsphere/nanofiber hybrid was produced by electrospinning. We can effectively control the morphology transformation from a pearl necklace-like nanofiber to a microsphere/nanofiber hybrid. The hybrid shows Pt-like oxygen reduction reaction activity both in acidic and basic solutions, making it one of the best non-noble metal oxygen catalysts.