Mn²⁺-doped Fe₃O₄ nanoparticles: a novel preparation method, structural, magnetic and electrochemical characterizations

A novel electrosynthesis procedure was applied to prepare manganese-doped iron oxide (Fe₃O₄) nanoparticles. The procedure involved depositing Fe₃O₄ nano-particles on a steel cathode from aqueous solution of (2 g/L) Fe(NO₃)₃, (1 g/L) FeCl₂ and (0.3 g/L) MnCl₂. Next the product was evaluated using X-ray diffraction (XRD), field emission electron microscopy (FE-SEM) and energy-dispersive X-ray (EDX). The final optimal product was found to contain 10 wt% of Mn²⁺ and the average size of the spherical Mn-Fe₃O₄ nano-particles was determined to be 20 nm. Further analysis of the produced particles using VSM proved it to have super-paramagnetic behavior (Ms = 47.25 emu g⁻¹, Mr = 0.22 emu g⁻¹, positive Mr = −0.703 emu g⁻¹, negative Mr = −1.15 emu g⁻¹, H _Ci  = 4.84 G, positive H _Ci  = 25.55 and negative H _Ci  = 15.85 G). The nanoparticles were studied using electrochemical techniques of cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy, and it was found that the nanoparticles possess a specific capacitance value of 202.5 F g⁻¹, and capacity maintain about 92.4% after 2000 cycles at 0.5 A g⁻¹, which indicated the particles have excellent potential for use in supercapacitors.