context: In order to evaluate the electrochemical performance of the obtained electrodes, two-electrode Zn–MnO2 batteries were assembled using COG@MnO2 as the cathode and COG@Zn as the anode in an aqueous electrolyte containing 2 M ZnSO4 and 0.1 M MnSO4. The typical cyclic voltammetry (CV) curves of the aqueous COG@MnO2//COG@Zn battery at different scan rates are shown in Fig. 3d. There are two reduction peaks at around 1.2 and 1.4 V, which should be ascribed to the zinc insertion into MnO2 and the subsequent reduction of Mn(IV) to the Mn(III)/Mn(II) states. Similarly, the oxidation peak and shoulder appear at 1.6–1.8 V, corresponding to Zn-extraction from the MnO2 cathode as the Mn(III)/Mn(II) states undergo oxidation to the Mn(IV) state. The overall reaction of the battery can be formulated as follows:
answer: COG@Zn