In Situ Investigation of the Electrodeposition Mechanism of Manganese Dioxide from a Citrate Electrolyte: The Effect of Intermediate Stabilization on Material Morphology

In this work, the electrodeposition of manganese dioxide in the presence of citrate anions is characterized using a combination of in situ electrochemical quartz crystal microbalance (EQCM), small angle X-ray scattering (SAXS), quasi-in situ atomic force microscopy (AFM) and ex situ transmission electron spectroscopy (TEM). Manganese dioxide was deposited onto a platinum substrate at 1.3 V (vs SCE) from solutions containing 0.01 mM MnSO4, 0.1 M Na2SO4 and manganese citrate concentrations of 0, 0.5, 2 or 4 mM. It was found that varying the citrate concentration changed the deposition mechanism by stabilising the Mn3+ intermediate formed by the oxidation of Mn2+. The different stability of the Mn3+ ion affects the rate of nucleation on the surface and subsequent growth of the film. This in turn, affects the morphology of the deposited material. Understanding the effects of the deposition mechanism on the resultant film morphology is necessary to optimise the properties of electrodeposited films for their various applications.