Investigation on the electrochemical performance of hausmannite Mn₃O₄ nanoparticles by ultrasonic irradiation assisted co-precipitation method for supercapacitor electrodes

Spinel type manganese oxide (Mn₃O₄) nanoparticles were synthesized by ultrasonic irradiation assisted co-precipitation method using PEG and NaOH. The formation of tetragonal hausmannite phase (Mn₃O₄) with spinel structure was confirmed from XRD and FTIR studies. The average crystallite size of Mn₃O₄ nanoparticles was determined from Scherrer formula (39.9 nm) and Williamson–Hall relation (36.5 nm). The presence of elements, the overall oxidation state of manganese (Mn²⁺, Mn³⁺ and Mn⁴⁺) and chemical composition of these nanoparticles were determined from Mn 2p, Mn 3s and O 1s spectra using XPS. The spherically shaped morphology of these nanoparticles was analysed by SEM. The expected chemical composition of Mn₃O₄ nanoparticles was analysed by EDS. The electrochemical performance of these Mn₃O₄ nanoparticles was studied by CV, CP and AC impedance analysis. The maximum specific capacitance of Mn₃O₄ nanoparticles was found to be 296 F/g at a current density of 1 A/g². Nyquist plot shows lower value of resistance that indicates the good electrical conductivity of the Mn₃O₄ electrode, which accounts for the improved electrochemical performance of the supercapacitors. Hence, the use of surfactant and the presence of ultrasonic irradiation in the synthesis process plays a dominant role in the electrochemical performance of Mn₃O₄ supercapacitors.