Oxygen reduction on Ag–MnO2/SWNT and Ag–MnO2/AB electrodes

Bifunctional catalysts (Ag–MnO2)/SWNT were prepared by using a simple chemical reduction route on single-walled carbon nanotubes (SWNT). Five weight percentage of Ag–MnO2 on SWNT was found to be the best loading in terms of current density. The (Ag–MnO2)/SWNT catalyst was characterized and the kinetics towards oxygen reduction reaction (ORR) was determined and compared with that of Ag–MnO2 on acetylene black (AB) catalyst. The number of exchanged electrons for the ORR was found to be close to four on both (Ag–MnO2)/SWNT and (Ag–MnO2)/AB. The kinetic rate constant of catalytic reaction for the two catalysts was of the same order. The zinc–air batteries with both catalysts were fabricated and examined. A stable discharge potential plateau appeared at approximately 1.2 and 1.1 V with discharge capacities 261 and 190 mAh/g, respectively.