Electrodeposition of manganese oxide from eutectic urea/choline chloride ionic liquid: An in situ study based on soft X-ray spectromicroscopy and visible reflectivity

Abstract

In this work, we describe a novel approach to the fabrication of MnO2, consisting in Mn electrodeposition from a choline chloride/urea eutectic ionic liquid bath followed by controlled electrochemical oxidation in an aqueous solution. Both electrodeposition and electro-oxidation processes have been studied by electrochemical and in situ spectroelectrochemical approaches. Synchrotron-based soft X-ray scanning microscopy and absorption spectroscopy were used to measure in situ the Mn valence distribution on the electrodes and within the cell. The oxidation process was followed in situ by visible reflectivity measurements: the different stages of the oxidation process could be discriminated dynamically on the basis of relative reflectivity changes. The capacitance of the electrochemically fabricated films has been measured with cyclic voltammetry and electrochemical impedance spectrometry.