Effects of morphology on the electrochemical performance of NiFe ₂ O ₄ nanoparticles with battery‐type behavior

Abstract We report the synthesis of NiFe ₂ O ₄ nanoparticles by the complexation EDTA‐citrate method under acidic (pH = 3) and basic (pH = 9) conditions. The structural, optical, vibrational, magnetic, and electrochemical properties were studied. The samples have crystallite sizes of 21 nm (pH 3) and 73 nm (pH 9), with rounded particles and layered structures. The ⁵⁷ Fe Mössbauer spectra at 12 K showed that both samples had an inverse spinel cation distribution. At 5 K, the sample prepared at pH 9 showed saturation magnetizations of about 50 emu/g. Raman spectra showed typical bands of NiFe ₂ O ₄ phase. The materials were tested as electrodes under alkaline condition. The cyclic voltammetry and charge‐discharge experiments indicated a battery‐type behavior, with maximun capacities of 65 and 5 C/g (at specific currents of 3 and 10 A/g) for samples prepared at pH 9 and 3, respectively. This work offers a route for obtaining NiFe ₂ O ₄ nanoparticles with different morphologies and sizes tuned by the synthesis conditions.