Hierarchical Nanosheet‐like CoNi2S4 Ternary Metal Sulfide for Oxygen‐Evolution Reactions Water Splitting and Supercapacitor Performance

A CoNi 2 S 4 ternary composite was prepared through hydrothermal‐mediated microemulsion approach, engaging a water–oil emulsion to obtain specific control over composition and morphology. The prepared composite later characterized via X‐ray diffraction spectroscopy and scanning electron microscopy that ensured its crystalline cubic structure, and porous interconnected spongy morphology, respectively. This specific morphology improved its surface area and electrochemical performance. The composite material employed for dual excellence. In oxygen‐evolution reaction, the prepared CoNi 2 S 4 material depicted a low Tafel slope of 27 mV dec − 1 at 10 mA cm − 2 with superior catalytic activity and sustained promising kinetics at maximum current densities. The electrochemical active surface area of prepared composite material is measured as 108.5 cm 2 based on the double‐layer capacitance ( C dl ) of 6.51 mF cm − 2 . Moreover, the CoNi 2 S 4 material illustrates remarkable performance for supercapacitor application, resulting a highest specific capacitance value about 1033 F/g at 1 A g − 1 , with cyclic stability about 87% and 91% after performance of 3000th cycles as determined by cyclic voltammetry and galvanostatic charge discharge performances, respectively. The energy density measurement for CoNi 2 S 4 nanocomposite reached a superior value of 29 Wh kg − 1 with an associated power density of 225 W kg − 1 . These outcomes demonstrate the CoNi 2 S 4 ternary composite material as a potential efficient material for dual excellence in energy storage and conversion performance.