Exploring the influence of solvothermal-reaction temperature on NiO nanostructures for enhanced electrochemical performance as electrode material in supercapacitors applications

This study examines the effect of solvothermal reaction temperatures (120–200 °C) on the structural, morphological, and electrochemical properties of NiO nanostructures. All samples exhibited a pure face-centered cubic phase, with surface morphologies varying with reaction temperature. In a three-electrode cell, NiO synthesized at 200 °C delivered a specific capacitance of 690 F g−1 at 0.5 A g−1, minimal charge transfer resistance of 100 Ω cm2, and a high diffusion rate, attributed to its substantial specific surface area (19 m2 g−1) and enhanced electrochemical active surface area (9.74 μF m−2). This performance is due to the flower-like morphology, which provides a larger surface area and improved electrochemical kinetics. A symmetric device achieved an impressive capacitance of 1755 F g−1, with an energy density of 877.5 Wh kg−1 and power density of 438.75 W kg−1, alongside remarkable cycling stability (98.98% retention after 10,000 cycles). The enhanced performance is attributed to the morphology at 200 °C, featuring a balanced microporous structure and conductivity that facilitate rapid ion diffusion and stable electric double layer formation.