Cobalt Nanoparticles Embedded in N, S Co‐Doped Carbon towards Oxygen Reduction Reaction Derived by in situ Reducing Cobalt Sulfide

Abstract Herein, a novel electrocatalysts of cobalt nanoparticles embedded in N, S co‐doped carbon matrix derived by in situ reducing Co 9 S 8 are designed and prepared successfully through two‐calcination methods, and applied for oxygen reduction reaction (ORR). Due to the large surface area and pore volume, richness of defects existing the carbon nanotubes, interaction of S species and N species and special direction of electron transfers between Co and S ions, the earth‐abundant and low‐cost CoSMe‐0.5‐800 presents a highly efficient ORR activity and stability. The onset potential, half‐wave potential and limiting current density of CoSMe‐0.5‐800 are 0.95 V, 0.85 V, and 4.31 mA cm −2 , which are higher than that of commercial Pt/C (0.93 V, 0.83 V, 4.19 mA cm −2 ). More importantly, the interaction between N and S heteroatoms in system gets revealed, that S resources can help to improve the degree of N doping and raise the ratio of pyridinic N species working as the active site for ORR. With the increase of S resources, electrons that should have been transferred from cobalt to sulfur have moved in the opposite direction, which has a negative effect on ORR active performance. This work shows the potential to design advanced Co‐based N, S co‐doped catalysts with high electrochemical performance and low cost, which could be applied for fuel cells and other devices.