Role of pH in Tailoring Ni-Co Hydroxide Nanostructures for Energy Storage Applications

Abstract

Nano-sized bimetallic cobalt-nickel hydroxide [NiCo(OH)4) with a 1:1 Co/Ni atomic ratio was synthesized via a surfactant-free co-precipitation-hydrothermal method, where the solution pH was systematically varied to direct structural evolution. The growth process begins with the nucleation of hydroxide nanoplates, followed by dissolution and recrystallization into stacked, hexagonal, disc-like architectures. Among the prepared samples, the material synthesised at pH 9.0 exhibited the most favourable electrochemical behaviour, delivering a high specific capacitance of 621 F g -1 at 0.5 A g -1 and retaining 400 F g -1 at 10 A g -1 , surpassing samples obtained at pH 8.0, 10.0, and 11.5. Morphological, structural, and spectroscopic characterisations confirmed that the enhanced performance of NCH-2 arises from its porous nanostructure, defect centres, and improved ion/electron transport kinetics for energy storage applications.