Synergistic Effect of Nitrogen in Cobalt Nitride and Nitrogen-Doped Hollow Carbon Spheres for the Oxygen Reduction Reaction

The need for inexpensive and high-activity oxygen-reduction-reaction (ORR) electrocatalysts has attracted considerable research interest over the past years. Herein, we report a novel hybrid that contains cobalt nitride/nitrogen-rich hollow carbon spheres (CoxN/NHCS) as a high-performance catalyst for ORR. The CoxN nanoparticles were uniformly dispersed and confined in the hollow NHCS shell. The performance of the resulting CoxN/NHCS hybrid was comparable with that of a commercial Pt/C at the same catalyst loading toward ORR, but the mass activity of the former was 5.7times better than that of the latter. The nitrogen in both CoxN and NHCS, especially CoxN, could weaken the adsorption of reaction intermediates (O and OOH), which follows the favorable reaction pathway on CoxN/NHCS according to the DFT-calculated Gibbs free-energy diagrams. Our results demonstrated a new strategy for the design and development of inexpensive, nonprecious-metal electrocatalysts for next-generation fuels.