Influence of the solution pH on the nanostructural, and electrochemical performance of electrolytic manganese dioxide

In this paper, during electrodeposition of electrolytic manganese dioxide (EMD) by anodic deposition from MnSO4 solution, the changing of pH is studied. The pH shows a decreasing trend. Two samples are electrodeposited at fixed pH (2 and 5) and their physico-chemical properties are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), the Barrett-Joyner-Halenda (BJH) method, and rechargeable alkaline manganese dioxide (RAM) battery tests. The results have confirmed that the pH of the solution has remarkable effects on the nanostructure, crystal structure, porosity, and the electrochemical performances of the EMD. Whereas the electrodeposition at pH 2 creates irregular multi-branched morphology with meso/microporosity, a large number of regular nanospheres with microporosity are obtained at pH 5. The battery tests study has revealed that α/γ-MnO2 electrodeposited at pH 2 exhibits good electrochemical performances, and the α-MnO2 displays very stable cycling behavior.