Investigation of cavity microelectrode technique for electrochemical study with manganese dioxides

Crystallized manganese dioxide powders (cryptomelane type α-MnO2 and birnessite type δ-MnO2) were electrochemically investigated in mild aqueous electrolytes with the cavity microelectrode (CME) technique. Cyclic voltammetry was performed with isolated MnO2 powder and mixed acetylene black/MnO2 powder. High electrochemical performance is achieved showing the pseudocapacitive behavior of cryptomelane and the birnessite signature, which is exhibited by large, intense and more defined peaks, than for a composite electrode. The microcavity electrode (about 10−3 mm3) allows studies with only a few micrograms of MnO2 powder in order to display its intrinsic electrochemical behavior and to improve the understanding of the role of the different components in the composite electrode performance.