Mo-doped one-dimensional needle-like Ni3S2 as bifunctional electrocatalyst for efficient alkaline hydrogen evolution and overall-water-splitting

Abstract

Hydrogen energy plays an important role in clean energy system and is considered the core energy source for future technological development owing to its lightweight nature, high calorific value, and clean combustion products. The electrocatalytic conversion of water into hydrogen is considered a highly promising method. An electrocatalyst is indispensable in the electrocatalytic process, and finding an efficient electrocatalyst is essential. However, the current commercial electrocatalysts (such as Pt/C and Ru) are expensive; therefore, there is a need to find an inexpensive and efficient electrocatalyst with high stability, corrosion resistance, and high electrocatalytic efficiency. In this study, we developed a cost-effective bifunctional electrocatalyst by incorporating molybdenum into nickel sulfide (Ni₃S₂) and subsequently tailoring its structure to achieve a one-dimensional (1D) needle-like configuration. The hydrogen production efficiency of nickel sulfide was improved by changing the ratio of Mo doping. By analyzing the electrochemical performance of different Mo-doped catalysts, we found that the Ni₃S₂-Mo-0.1 electrocatalyst exhibited the best electrocatalytic effect in 1 M KOH; at a current density of 10 mA cm⁻², it exhibited overpotentials of 120 and 279 mV for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively; at a higher current density of 100 mA cm⁻², the HER and OER overpotentials were 396 and 495 mV, respectively. Furthermore, this electrocatalyst can be used in a two-electrode water-splitting system. Finally, we thoroughly investigated the mechanism of the overall water splitting of this electrocatalyst, providing valuable insights for future hydrogen production via overall-water-splitting.