Co/N–C nanotubes with increased coupling sites by space-confined pyrolysis for high electrocatalytic activity

Searching low cost and non-precious metal catalysts for high-performance oxygen reduction reaction is highly desired. Herein, Co nanoparticles embedded in nitrogen-doped carbon (Co/N–C) nanotubes with internal void space are successfully synthesized by space-confined pyrolysis, which effectively improve the cobalt loading content and restrict the encapsulated particles down to nanometer. Different from the typical conformal carbon encapsulation, the resulting Co/N–C nanotubes possess more cobalt nanoparticles embedded in the nanotubes, which can provide more coupling sites and active sites in the oxygen reduction reaction (ORR). Moreover, the one-dimensional and porous structure provides a high surface area and a fast electron transfer pathway for the ORR. And the Co/N–C electrode presents excellent electrocatalytic ORR activity in terms of low onset potential (30 mV lower than that of Pt/C), small Tafel slop (45.5 mV dec⁻¹) and good durability (88.5% retention after 10,000 s).