Amorphous MoS2 coated Ni3S2 nanosheets as bifunctional electrocatalysts for high-efficiency overall water splitting

Abstract

Efficient non-noble metals bifunctional electrocatalysts play a significant role in both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) for overall water splitting. Herein, amorphous MoS2 (a-MoS2) coated Ni3S2 with three-dimensional nanosheets composite architecture supported on nickel foam (a-MoS2-Ni3S2/NF) was prepared via hydrothermal vulcanization Ni(OH)2/NF using thiourea and sodium molybdate dihydrate. In this process, the network structure of Ni3S2 nanosheets was primarily formed by in situ vulcanization of the Ni(OH)2 on nickel foam (NF) and was covered by the amorphous MoS2 (a-MoS2) nanoflakes as a skeleton at the same time. Not only did the hierarchical nanosheets nanoarrays and self-supported composite architecture of a-MoS2-Ni3S2/NF prevent the accumulation of nanoflakes, increase the active surface area and expose more active sites, but also facilitated the penetration of electrolytes and the transfer of charge/mass. Meanwhile, the synergistic effect between the a-MoS2 nanoflakes with highly disordered structure and Ni3S2 substrates with high conductivity significantly enhanced the HER and OER activity. The nanosheets composite structure of a-MoS2-Ni3S2/NF demonstrated an extremely low overpotential of 81 at 10 mA cm−2 for HER and 150 mV at 100 mA cm−2 for OER in alkaline conditions, respectively. In particular, when taken as both positive and negative electrodes to the full water electrolysis under alkaline medium, the bifunctional electrocatalyst of a-MoS2-Ni3S2/NF only required the battery voltage of 1.54 V at 100 mA cm−2.