ZIF-derived graphene coated/Co9S8 nanoparticles embedded in nitrogen doped porous carbon polyhedrons as advanced catalysts for oxygen reduction reaction

Development of efficient electrocatalysts for the oxygen reduction reaction (ORR) is vitally important for the commercialization of metal-air batteries. In this work, we demonstrate a novel graphene coated/Co9S8 nanoparticles-embedded nitrogen doped porous carbon dodecahedron hybrid (Co9S8/NPCP@rGO) prepared by the pyrolysis and sulphuration of precursors composing of graphene oxide and zeolitic imidazolate-frameworks (ZIP). The Co9S8/NPCP@rGO hybrid is used as a highly efficient nonprecious metal electrocatalyst for oxygen reduction and exhibits more positive onset potential and half-wave potential, higher limiting current density, lower Tafel slope, and better durability and methanol tolerance in alkaline media in comparison to the commercial 20 wt.% Pt/C catalyst. The greatly improved electrocatalytic performance of Co9S8/NPCP@rGO can be attributed to the unique structure with Co9S8 nanoparticles dispersed uniformly inside nitrogen doped porous carbon matrix, and the synergistic effect between Co9S8/NPCP polyhedral hybrid and rGO. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.