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

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 MoS 2 (a-MoS 2 ) coated Ni 3 S 2 with three-dimensional nanosheets composite architecture supported on nickel foam (a-MoS 2 -Ni 3 S 2 /NF) was prepared via hydrothermal vulcanization Ni(OH) 2 /NF using thiourea and sodium molybdate dihydrate. In this process, the network structure of Ni 3 S 2 nanosheets was primarily formed by in situ vulcanization of the Ni(OH) 2 on nickel foam (NF) and was covered by the amorphous MoS 2 (a-MoS 2 ) nanoflakes as a skeleton at the same time. Not only did the hierarchical nanosheets nanoarrays and self-supported composite architecture of a-MoS 2 -Ni 3 S 2 /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-MoS 2 nanoflakes with highly disordered structure and Ni 3 S 2 substrates with high conductivity significantly enhanced the HER and OER activity. The nanosheets composite structure of a-MoS 2 -Ni 3 S 2 /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-MoS 2 -Ni 3 S 2 /NF only required the battery voltage of 1.54 V at 100 mA cm −2 .