Constructing a 1T-MoS2/Ni3S4 heterostructure to balance water dissociation and hydroxyl desorption for efficient hydrogen evolution

Abstract

Alkaline water electrolysis is a viable technique for large-scale hydrogen production. The metallic polymorph of molybdenum disulfide (1T-MoS₂) has been proven to be an efficient electrocatalyst for the hydrogen evolution reaction (HER) in acidic electrolytes. However, its catalytic activity under alkaline conditions is substantially lower than under acidic ones. This is due to the sluggish water adsorption and dissociation dynamics. In this study, a 1T-MoS₂/Ni₃S₄ heterostructure was constructed by vertically growing 1T-MoS₂ nanosheets on Ni₃S₄ nanosheets. Experiments and theoretical calculations demonstrated that electrons transfer from Ni₃S₄ to 1T-MoS₂ at the heterointerfaces. This electron re-arrangement balances the energy between water dissociation and hydroxyl desorption on the Ni sites and optimizes the free energy of hydrogen adsorption (ΔG_H*) on the Mo-edge sites. This synergistic effect accelerates both water splitting on the Ni site and hydrogen adsorption/desorption on the Mo-edge site at the heterointerface. Consequently, the 1T-MoS₂/Ni₃S₄ heterostructure shows significantly boosted alkaline HER activity, with a small overpotential of 44 mV at 10 mA cm⁻² and a Tafel slope of 43 mV dec⁻¹ in 1 M KOH. In particular, at high current densities (j > 100 mA cm⁻²), it outperforms state-of-the-art Pt/C.