CV curves of the graphene/MnO
composite electrodes. The curves were measured at different scan rates of 5, 10, 20, 50, and 100 mV/s (from inner to outer). From (a) to (c), the microwave reaction times are 5, 10, and 15 min, respectively. Note that the mass of the active material is similar for (a) and (c), which is, however, almost twice as that for (b).