Manganese dioxide nanoparticles synthesized by electrochemical method and its catalytic activity towards oxygen reduction reaction

Manganese dioxide having nanorod and nanoflake morphologies have been successfully prepared by electrolysis of KMnO₄ at a temperature of 60°C. The acidity of the solution substantially influenced the particle morphology. The particles had nanorod morphology at a very acid solution (pH 0.2) whereas they had nanoflake shape at the base condition (pH 9). X-ray diffraction analysis revealed that the particles generated at very acid condition were -MnO₂. On the other hand, the particles synthesized at base condition were amorphous MnO₂. The electrocatalytic activity towards oxygen reduction reaction (ORR) of the materials was studied in oxygensaturated 0.6M KOH solution. The electrons transferred per oxygen molecules of ORR for nanorod and nanoflake MnO₂ particles were 2.23 and 1.75, respectively. The results suggest that nanorod MnO₂ particles exhibit better ORR activity corresponding to 2-electron transferred ORR mechanism.