Boosting Oxygen Reduction Catalysis with N‑doped\nCarbon Coated Co₉S₈ Microtubes

Abstract

Herein,\nnitrogen-doped carbon coated hollow Co₉S₈ microtubes\n(Co₉S₈@N–C microtubes)\nare prepared through a facile solvothermal procedure, followed by\ndopamine polymerization process together with a post-pyrolysis which\npresent excellent electrocatalytic activity for oxygen reduction reaction\n(ORR). The Co₉S₈ within the hollow Co₉S₈@N–C microtubes presents a well-defined single-crystal\nstructure with dominated (022) plane. To obtain desired electrocatalyst,\nthe annealing temperature and the thickness of carbon layer tuned\nby changing the dopamine concentration are optimized systematically.\nThe electrochemical results demonstrate that the coordination of the\nN-doped carbon layer, exposed (022) plane, and hollow architecture\nof Co₉S₈ microtubes calcined at 700 °C\naffords outstanding ORR performance to Co₉S₈@N–C microtubes. The moderate thickness of the carbon layer\nis crucial for improving ORR activity of Co₉S₈@N–C microtubes, while increasing or decreasing the thickness\nwould result in activity decrease. More importantly, the N-doped carbon\nlayer can protect inner Co₉S₈ from undergoing\naggregation and dissolution effectively during the ORR, resulting\nin excellent electrocatalytic stability.