Nitrogen Incorporated in Cobalt Sulfide/Graphene Hybrid Catalysts Affording High Activity for Overall Water Splitting.

Water electrolysis is an advanced and sustainable energy conversion technology used to generate H 2 . However, the low efficiency of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) hampers the overall-water-splitting catalytic performance. Here, we highlighted a hybrid catalyst constructed from N-doped CoS 2 nanoparticles on N,S-co-doped graphene nanosheets (N-CoS 2 /G) using a facile method that exhibits excellent bifunctional activity. Introduction of N-atoms not only promotes the adsorption of reaction intermediates, but also bridge the CoS 2 nanoparticles and graphene to improve electron transfer. Moreover, using thiourea as both N- and S-sources ensures synthesis of much smaller sized nanoparticles with more surface active sites. Surprisingly, the N-CoS 2 /G exhibits superior catalytic activity with a low overpotential of 260 mV for the OER and 109 mV for the HER at a current density of 10 mA cm -2 . Moreover, the assembled N-CoS 2 /G:N-CoS 2 /G electrolyzer substantially expedites overall water splitting with a voltage requirement of 1.58 V to reach 10 mA cm -2 , which is superior to most reported Co-based bifunctional catalysts and other non-precious-metal catalysts. This work provides a new strategy to advanced bifunctional catalysts for water electrolysis.