Synthesis, microstructure and electrochemical characterization of NiMn₂O₄ nanoparticles via a simple citric acid method

NiMn2O4 has an inverse spinel structure similarly to Co3O4 and NiCo2O4, but NiMn2O4 is much cheaper than these cobalt containing materials. Here, we report synthesis, microstructure and electrochemical characterization of NiMn2O4 nanoparticles via a simple citric acid method. Ni(CH3COO)2·4H2O (1.5 mmol) and Mn(CH3COO)2·4H2O (3.0 mmol) were dissolved in distilled water (25 mL), and citric acid (3.75 mmol) was added and stirred for 2 h to obtain transparent blue-green solution. The solution was open-heated at 90 °C for 24 h, and heated at 170 °C for 2 h to obtain a xerogel. The xerogel precursor was pestled and calcined at 400 °C for 4 h in air to obtain a NiMn2O4 powder. X-ray diffraction, N2 adsorption/desorption and transmission electron microscopy with energy dispersive X-ray spectroscopy revealed that single-phase NiMn2O4 mesoporous nanoparticles were successfully synthesized from eco-friendly acetates ingredients by the low-cost citric acid method. The specific surface area and pore size of the NiMn2O4 mesoporous nanoparticles were 211.3 m2/g and ∼4 nm, respectively. The NiMn2O4 electrode successfully worked as a supercapacitor.