Achieving superior performance for oxygen electrode catalyst by the assistance of NaCl to construct cobalt sulfide on nitrogen and sulfur dual-doped graphene

Developing highly active catalysts to promote oxygen reduction reaction and oxygen evolution reaction is of utmost importance. Herein, the Co4S3/NSG-NaCl catalyst is prepared via a NaCl-guided hydrothermal method. Control experiments by replacing NaCl with KCI, KBr, NaNO3, CaCl2 and NaBr reveal that NaCl promotes a more efficient oxygen electrode catalysis results due to its high affinity and high ionicity. By varying the amount of the raw materials, optimized compositions are contained in the catalyst. Physical characterization indicates the optimized catalyst is of high specific BET surface area (similar to 181 m(2) g(-1)) and porous structure, which enable to expose more active sites, and facilitate more rapid mass transfer at the interface of gas-liquid-solid. XPS measurements suggest the formation of pyridinic N, graphitic N, Co N and Co S active species. Stemming from the synergistic effects between Co4S3 and nitrogen and sulfur dual-doped graphene, the optimized Co4S3/NSG-NaCl hybrid show excellent catalytic activity and stability for both oxygen reduction reaction and oxygen evolution reaction under corrosive media. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.