MnO2 Nanoparticles Prepared by Alternating Monopolar Arrangement Electrolysis and Their Electrochemical Performances

Abstract

Manganese dioxide nanoparticles have been successfully synthesized by the electrolysis method using 4-pairs carbon electrode in the alternating monopolar arrangement. The advantage of the arrangement is a significant increase in the product yield compared to the single pair electrodes. KMnO4 solution in pH 0.2 and 9 were used as precursor and electrolyzed for thirty minutes at a temperature of 60 °C. The generated particles resulted from electrolysis in pH 0.2 (MnO2-A) and in pH 9 (MnO2-B) were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), and nitrogen adsorption-desorption isotherms to examine their crystallinity, morphology, and the specific surface area. The α-MnO2 was observed for MnO2-A particles and amorphous for MnO2-B particles. The particles size of MnO2-A was larger than that of MnO2-B with the specific surface areas of 396 and 98 m2/g, respectively. The higher surface area of MnO2-A corresponding to the channel pore of short rod-like morphology. On the other hand, MnO2-B contributed to the spherical particles. The measurements of cyclic voltammetry (CV) were also carried out to measure their specific capacitances and their performance for oxygen reduction reaction (ORR) electrocatalyst. MnO2-A exhibited higher specific capacitance of 13.57 F/g compared to MnO2-B that only had 3.62 F/g. In addition, MnO2-A also gave better performance as ORR electrocatalyst measured in O2-saturated 0.6 M KOH resulted in 2.69 transferred electron number per oxygen molecule.