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

Herein, a novel electrocatalysts of cobalt nanoparticles embedded in N, S co-doped carbon matrix derived by in situ reducing Co9S8 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.