Understanding the role of precursor concentration in the hydrothermal synthesis of nickel phosphate hydrate for supercapacitors

With the developing technology, the demand for energy storage devices has been ever-increasing. Supercapacitors over the years have delivered high power density along with a moderate energy density. Herein, this study reports Nickel Phosphate Hydrate (Ni(PO₄)₃*8H₂O) (NPH) as a battery-type electrode which was synthesized using a hydrothermal method. The formation of NPH on the nickel (Ni) foam was verified by the X-ray diffraction (XRD) technique which provided information about the monoclinic structure and the “I2/m” space group of the material. The morphology of the material was studied using scanning electron microscopy (SEM) which demonstrated a micro-slab like morphology. The electrochemical characteristics were evaluated in a 1 M KOH electrolyte with a potential window of − 0.2 and 0.55 V vs. SCE, the electrode delivered an areal capacitance of 3475.76 mF cm⁻² at 10 mA cm⁻². Furthermore, the material delivered an energy density of 173.78 µWh cm⁻² while retaining ~ 84.74% of its initial capacitance over 1000 charge-discharge cycles showing its promising characteristics for the future of energy storage devices.