The influence of nanostructure and electrolyte concentration on the performance of nickel sulfide (Ni3S2) catalyst for electrochemical overall water splitting

Developing nonprecious nanostructured electrocatalysts, exhibiting high catalytic activity in combination with excellent stability, has an enormous potential to replace noble-metal-based catalysts for Hydrogen production through electrochemical water splitting. In this study, a facile method is used for the synthesis of three different hierarchical nanostructures of nickel sulfide (Ni3S2) including nanosheets, nanorods, and multiconnected nanorods that are directly grown on 3D nickel foam (NF). These nanostructured electrocatalysts are evaluated for electrochemical water splitting in alkaline media using four different concentrations to understand the effect of nanostructure and ion concentration on the efficiency. Among different combinations of structure and electrolyte concentration, the Ni3S2 in the form of nanosheets exhibited the best electrocatalytic performance for hydrogen evolution reaction (HER) as well as oxygen evolution reaction (OER) in 3.0 M alkaline solution. The hierarchical Ni3S2 nanosheets exhibited a high electrochemically active surface area, which facilitated the charge transport phenomenon along the electrode–electrolyte interface in a higher electrolyte concentration that improved the reaction kinetics so as overall water splitting. The developed Ni3S2 nanosheets required an overpotential of 110 mV (@10 mA cm−2) and 211 mV (@100 mA cm−2) for HER and OER, respectively in 3.0 M electrolyte concentration. This work provides insight into how the materials’ nanostructures and electrolyte concentration could be utilized to improve the electrocatalytic performance for an overall water-splitting process, and the concept could be applied for material designing and conditions optimization for other catalytic applications.