Self−supported Ni3S2 nanoarrays as multi−functional catalysts for efficient alkaline water and seawater electrolysis

The development of efficient non−precious metal catalysts is of critical importance for advancing water splitting technology. Through rational morphological engineering, key parameters such as specific surface area, the density of exposed active sites, and mass transport pathways can be simultaneously optimized, thereby directly enhancing reaction kinetics. In this study, self−supported Ni 3 S 2 nanoarrays were synthesized via a sequential pretreatment and sulfidation strategy, utilizing nickel foam as both the nickel source and the growth substrate. The resulting nanoarray structure proved to be an efficient and durable electrocatalyst for water splitting. In 1.0 M KOH solution, the overpotential of the HER (69 mV) approaches that of Pt/C, whilst the OER overpotential (199 mV) outperforms RuO 2 , yielding an overall water splitting voltage of 1.54 V (10 mA cm −2 ). The same excellent catalytic activity was also exhibited in simulated seawater with overpotentials of 98 and 225 mV for HER and OER, respectively. The main reason for the enhanced catalyst activity is attributed to the unique nanoarray morphology that exposes a larger electrochemically active specific surface area and provides abundant active sites. More importantly, there is a strong coupling between nickel foam substrate and Ni 3 S 2 nanoarrays catalyst. The strong Ni−S chemical bond formed during the hydrothermal preparation much improves the catalytic activity, electronic conductivity and structural stability.