Effect of reducing agents on structural, morphological, optical and electrochemical properties of Mn2O3 nanoparticles by co-precipitation method

Abstract

Abstract In this work, two different reducing agents namely sodium hydroxide and potassium hydroxide (NaOH and KMnO4) were used to synthesis of manganese oxide (Mn2O3) nanoparticles by the co-precipitation method and examined for the electrochemical applications. The as-prepared Mn2O3 nanoparticles using NaOH precursor, dried in a hot oven at 80 °C for 6 h (MN-1) and then annealed for 7 h at 600 °C (MN-2). Similarly, Mn2O3 nanoparticles were prepared using KMnO4 precursor, dried in a hot oven at 80 °C for 6 h (MK-1) and then annealed for 7 h at 450 °C (MK-2), respectively. The influences of reducing agents on structural, morphological and optical properties were investigated. The structural analysis revealed the prepared samples had tetragonal crystal structures with better crystallinity. FT-IR spectral analysis revealed the characteristic bonds of Mn–O–Mn were observed in the region of 486–573 cm−1. The FE-SEM and HR-TEM images showed coral-like and nanorod structures for samples MN-2 and MK-2, with exhibited lattice value of 0.27 nm related to the (222) plane. The presence of the elements manganese (Mn) and oxygen (O) was confirmed by EDAX mapping. The XPS study confirmed that the oxidation state of the prepared samples was +2. The UV-Vis spectra suggested that the adsorption edge was blue-shifted compared to the sample MN-2. Cyclic voltammetry (CV) and galvanostatic charge–discharge experiments demonstrated that charge storage in Mn2O3 exhibited faradic-dominated capacitive behavior. MN-2 nanorod structures were obtained at excellent specific capacitance value of 196 F g−1 compared to MK-2 nanoparticles. Based on this study, Mn2O3 nanoparticles was recommended as exceptional electrode materials for efficient supercapacitor applications due to its superior electrical conductivity, large surface area and redox properties.