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

Abstract

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.