Graphene supported flower-like NiS2/MoS2 mixed phase nano-composites as a low cost electrode material for hydrogen evolution reaction in alkaline media

Abstract

Modified bimetallic chalcogenides with numerous active sites of appropriate structures for extensive water splitting in alkaline hydrogen evolution reaction (HER) are quite challenging. In this study, we have designed a graphene nano-sheet anchored NiS2/MoS2 heterostructure through a facile two-step method and have employed them towards HER. To evaluate the performance of the NiS2/MoS2@GNS, The crystalline phase, morphology and material purity are evaluated by XRD, SEM, high resolution transmission microscopy HR-TEM and EDS. In addition, the electrochemical performance of the as-synthesized NiS2/MoS2@GNS composites and other electrocatalysts are tested towards the HER in 1 M KOH electrolyte. It is noted that the graphene nano-sheet (GNS) anchored NiS2/MoS2 composite shows an excellent electrocatalytic activity with a less overpotential of 130 mV at current density (|j|) of 10 mA cm−2 and a low Tafel slope of 40 mV dec−1 compared with pristine NiS2/MoS2 material (141 mV at 10 mA cm−2 and Tafel slope of 48 mV dec−1). Furthermore, it possessed good stability for 1000 cycles and performed time-dependant current density for 10 h at a limited overpotential of 130 mV. The high synergistic effect between NiS2/MoS2 and GNS in promotion of hydrogen (H2) generation efficiency is ascribed to more active sites, low charge transfer resistance and great electrochemical kinetics which justified the use of NiS2/MoS2@GNS hybrid material as a best alternative to replace noble metal for efficient HER.