Regulating electronic properties of nickel-iron layered double hydroxide with molybdenum disulfide via low-temperature plasma irradiation for efficient overall water splitting

Abstract

Efficient electrocatalysts are essential in water electrolysis for affordable green hydrogen production. Here, by using a low-temperature plasma irradiation method, molybdenum sulfide in-situ formed on nickel iron layered double hydroxide loaded at Ni foam (MoS₂/NiFe-LDH@NF) is constructed. X-ray diffraction, scanning electron microscopy and transmission electron microscopy confirm the microstructures of the MoS₂/NiFe-LDH networks. X-ray photoelectron spectroscopy proves the formation of active vacancies and electronic regulation between NiFe-LDH and MoS₂, which downshifts the d-band level of nickel and iron by 0.24 eV and 0.29 eV, respectively, and thus optimizes the adsorption/desorption equilibrium of intermediates on MoS₂/NiFe-LDH, indicated by density functional theory calculations. The resulting MoS₂/NiFe-LDH@NF catalyst exhibits high bifunctional activities in the alkaline water splitting. During the hydrogen evolution reaction, remarkably low overpotentials of 85/209 mV are needed to reach 10/50 mA cm⁻², and only 100 mV and 150 mV overpotentials are required during oxygen evolution reaction to achieve 10/50 mA cm⁻², respectively. More importantly, the overall water electrolysis employing MoS₂/NiFe-LDH@NF results in a cell voltage of 1.495 V at current density of 10 mA cm⁻², lower than that (1.63 V) of the commercially paired IrO₂||Pt/C electrocatalyst, accompanied by a long-term stability during 500 h operations. This work demonstrates that the low-temperature plasma irradiation is an effective and simple strategy to prepare robust electrocatalyst for efficient water splitting.