Preparation of β-MnO2 nanobelt and its electrocatalytic activity for oxygen reduction

Manganese oxide was synthesized by the hydrothermal method through oxidizing MnSO4 with HMnO4 at 150 degrees C using cetyltrimethylammonium bromide as template. X-ray diffraction and scanning electron microscopy showed that the product was beta-MnO2 nanobelt. The beta-MnO2 nanobelt and electrolytic manganese dioxide (EMD) were used as catalyst to make air diffusion electrodes by mixing activated carbon and polytetrafluoroethylene. In 6 mol/L KOH aqueous solution, current-potential polarization curves showed that the air electrode potential with beta-MnO2 nanobelt catalyst was more positive by 30 - 60 mV than that of EMD, and the optimal content of beta-MnO2 nanobelts in the electrocatalyst was 35%. At the typical current density 40 mA/cm(2) of a Zn/air battery, the cell with the beta-MnO2 nanobelt catalyst had stable discharge voltage up to 1.12 V.