A facile method to prepare high-purity magnetite nanoparticles by electrooxidation of iron in water using a pulsed direct current

High-purity magnetite (Fe₃O₄) nanoparticles were successfully synthesized via the electrooxidation of iron in an aqueous system using a pulsed direct current (pulsed DC). The pure iron to be electrooxidized was electroplated on a steel plate, which was then used as a sacrificial anode in the electrochemical system. The electrolyte used was demineralized water, either with or without added NaOH, which was used to vary the pH of the solution, between 7 and 10. We showed that the pulsed DC significantly enhanced the purity of the magnetite that was formed. The FeOOH impurities that are typically present when continuous DC is used were not observed. The particles produced using the proposed method were nearly spherical in shape. The size of the particles ranged from 7 to 23 nm depending on the conditions of synthesis, namely, the pulse frequency, duty cycle, and pH. The magnetite nanoparticles exhibited ferromagnetic properties, with values of saturation magnetization ranging from 18 to 55 emu/g. The results obtained from thermal gravimetric/differential thermal analysis revealed that magnetite was converted into maghemite at a temperature of approximately 200 ° C and into hematite under further heating to 500°C.