Impact of sonochemical and chemical precipitated synthesis of porous nickel manganite (NiMn₂O₄) electrodes for supercapacitor applications

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 Ω, respectively). These findings highlight the superior capacitive performance of S-NMO and its strong potential as a high-performance electrode material for supercapacitors.