Electrochemical Performance of MnO2-based Air Cathodes for Zinc-air Batteries

This paper compares the oxygen reduction on four MnO2-based air cathodes assembled in home-made electrochemical cells, with some particular observations on -MnO2 cathode. The results show that the catalytic activity decreases in the following order: electrolytic MnO2 (EMD) > natural MnO2 (NMD) > -MnO2 > -MnO2. The maximum power density of the zinc-air battery with EMD as the catalyst reaches up to 141.8mWcm(-2) at the current density of 222.5mAcm(-2), which is about 60%, 20% and 10% higher than that of -MnO2 (90.0mWcm(-2) at 120.3mAcm(-2)), -MnO2 (121.5mWcm(-2) at 150.4mAcm(-2)) and NMD (128.2mWcm(-2) at 207.8mAcm(-2)), respectively. It is believed that its unique crystal structure and biggest BET surface area make EMD have the smallest charge transfer resistance (R-ct), thus EMD has the highest activity.