N, S-codoped graphene loaded Ni-Co bimetal sulfides for enhanced oxygen evolution activity

Enhanced catalysis for electrochemical oxygen evolution is essential for water electrolyzes and metal-air batteries. Bimetal sulfides are recently emerged as effective catalysts for electrochemical oxygen evolution. In this study, Ni-Co bimetal sulfide nanounits loaded on N, S-codoped graphene nanosheets were synthesized, which were then evaluated as the catalysts for oxygen evolution reaction in alkaline medium. An obvious enhancement of the catalytic activity is demonstrated by the introduction of N, S-codoped graphene nanosheets as conductive substrates. With the optimized Ni-Co sulfide/N, S-codpoed graphene composites, the overpotential is only 272 mV to drive a current density of 10 mA cm(-2) in 1 M KOH, much lower than those of pristine Ni-Co sulfide (434 mV) and Ni-Co sulfide loaded on reduced graphene oxide (335 mV). The improved electrocatalytic activity of Ni-Co sulfide/N, S-codpoed graphene can be attributed to the improved electrochemical active specific area due to the synergistic effect between nickel sites and cobalt sites, the substrate effect of N, S co-doped graphene. These findings would provide new hints for the design and development of sulfide-based oxygen evolution catalyst.