Figure 5

Zn–air batteries. 20 wt% carbon black used for RuO2@C. Pt loading of Pt/C is 20 wt%. (a) Discharge rate capability at 20 mA cm−2 charge. ORR proceeds on air electrodes. The currents used for discharge are indicated in mA (geometric electrode area = 2.8 cm2). (b) Charge rate capability at 20 mA cm−2 discharge. OER proceeds on air electrodes. The currents used for charge are indicated in mA (geometric electrode area = 2.8 cm2). (c and d) Galvanostatic charge/discharge cycles at 20 mA cm−2.