Abstract

This study investigates the influence of sonochemical and chemical precipitation methods on the structural, morphological, and electrochemical properties of porous NiMn2O4 (NMO) nanoparticles. The powder X-ray diffraction reveals average crystallite sizes of 19 nm for sonochemically synthesized (S-NMO) and 5 nm for chemically precipitated (C-NMO) samples. The FTIR confirms the presence of metal-oxide functional groups, while X-ray photoelectron spectroscopy identifies mixed valence states of Ni2+/Ni3+ and Mn3+/Mn4+ in the spinel structure. The field emission scanning electron microscopy shows that S-NMO exhibits a mixed morphology of nanorods and flakes, whereas C-NMO forms randomly arranged nanorods. The BET analysis indicates mesoporosity with surface areas of 87.99 m2g-1 for S-NMO and 66.87 m2g-1 for C-NMO. The electrochemical measurements demonstrate that S-NMO delivers a specific capacitance of 1061 F.g-1 at 5 mVs-1, outperforming C-NMO (695 F.g-1), with both materials exhibiting negligible equivalent series resistance (1.01 and 1.10 Omega, respectively). These findings highlight the superior capacitive performance of S-NMO and its strong potential as a high-performance electrode material for supercapacitors.