Highly electrocatalytic performance of bimetallic Co–Fe sulfide nanoparticles encapsulated in N-doped carbon nanotubes on reduced graphene oxide for oxygen evolution

We rationally design and construct a heterostructured hybrid with reduced graphene oxide served as a platform to in-situ grow N-doped bamboo-like carbon nanotubes encapsulating bimetallic Co–Fe sulfide nanoparticles through a two-stage pyrolysis succeeded by an evaporating sulfurization process (denoted as Co x Fe 1- x S 2 @N-CNTs/rGO). By tuning the Co/Fe ratio, the optimal Co 0.6 Fe 0.4 S 2 @N-CNTs/rGO exhibits a remarkable oxygen evolution reaction (OER) performance in 1.0 M KOH, in which the overpotential at 10 mA cm −2 and Tafel slope are recorded as 248 mV ( vs . RHE) and 58.3 mV dec −1 , respectively, outmaneuvring commercial RuO 2 and most Co/Fe sulfide-based catalysts in recent peer reports. Comprehensive experiment results unravel that the outstanding OER electrocatalytic performance owes to the reinforced synergy between CoS 2 and FeS 2 , the heterostructures constituted by partial CoS 2 and FeS 2 , the confining effect of N-CNTs/rGO for CoS 2 and FeS 2 nanoparticles, and the high conductivity and large surface of N-CNTs/rGO.