Simultaneously Incorporating Atomically Dispersed Co‐Nx Sites with Graphitic Carbon Layer‐Wrapped Co9S8 Nanoparticles for Oxygen Reduction in Acidic Electrolyte

Co₉S₈ nanoparticles, when incorporated with the Co single atom catalysts, provide a synergistic catalyst for oxygen electroreduction in acid solution. Catalysts composed of both components are stable under operating conditions and have been shown to operate well within a fuel cell environment.

Abstract

A facile yet robust synthesis is reported herein to simultaneously incorporate atomically dispersed Co-N_x sites with graphitic layer-protected Co₉S₈ nanoparticles (denoted as Co SACs+Co₉S₈) as an efficient electrocatalyst for oxygen reduction in acidic solution. The Co SACs+Co₉S₈ catalyst shows low H₂O₂ selectivity (∼5 %) with high half-wave potential (E_1/2) of ∼0.78 V_RHE in 0.5 M H₂SO₄. The atomic sites of the catalyst were quantified by a nitrite stripping method and the corresponding site density of the catalyst is calculated to be 3.2×10¹⁸ sites g⁻¹. Besides, we also found the presence of a reasonable amount of Co₉S₈ nanoparticles is beneficial for the oxygen electrocatalysis. Finally, the catalyst was assembled into a membrane electrode assembly (MEA) for evaluating its performance under more practical conditions in proton exchange membrane fuel cell (PEMFC) system.

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