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

Abstract

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 CoxFe1-xS2@N-CNTs/rGO). By tuning the Co/Fe ratio, the optimal Co0.6Fe0.4S2@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 RuO2 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 CoS2 and FeS2, the heterostructures constituted by partial CoS2 and FeS2, the confining effect of N-CNTs/rGO for CoS2 and FeS2 nanoparticles, and the high conductivity and large surface of N-CNTs/rGO.