A template-free method for preparation of cobalt nanoparticles embedded in N-doped carbon nanofibers with a hierarchical pore structure for oxygen reduction.

Designing and preparing porous materials without using any templates is a challenge. Herein, single-nozzle electrospinning technology coupled with post pyrolysis is applied to prepare cobalt nanoparticles embedded in N-doped carbon nanofibers with a hierarchical pore structure (HP-Co-NCNFs). The resultant HP-Co-NCNFs have lengths up to several millimeters with an average diameter of 200 nm and possess abundant micro/meso/macropores on both the surface and within the fibers. Such a microstructure endows the surface area as high as 115 m(2)  g(-1) . When used as an electrocatalyst for the oxygen reduction reaction (ORR), the HP-Co-NCNFs exhibit outstanding electrochemical performance in terms of activity, methanol tolerance, and durability. The hierarchically porous structure and high surface area can effectively decrease the mass transport resistance and increase the exposed ORR active sites. The sufficient amount of exposed ORR active sites along with accessible transport channel and enhanced electrical conductivity may be responsible for the good electrocatalytic performance.