Development of electrode materials based on manganese oxides for anodic oxidation of organic pollutants

The electrodes made of manganese oxides represent an interesting family of materials, which are today primarily used as cathodes in alkaline batteries and lithium-ion batteries. A so far less studied application is their use as anodes in the electrochemical treatment of compounds toxic and/or refractory to biodegradation. In this research, we present the results related to the electrocatalytic capacity of electrodes formed from films of manganese oxides deposited by chemical or electrochemical way, in the degradation of solutions containing the azo-methyl-orange dye. The electrodes were characterized by morphological analysis and, in order to evaluate the efficiency of electrochemical treatment for decolorization and subsequent mineralization, electrolyses under galvanostatic conditions were conducted in a reactor without separation. The results obtained show that the electrodes of manganese exhibit similar behavior to the diamond, with the production of hydroxyl radical from the discharge of the water but, unlike these, they have a low production capacity of active chlorine. This characteristic makes them particularly attractive for use in processes where there is an interest in keeping low the production of chloro-compounds. The main limitation found in this initial research was that of a poor adhesion to the substrate and then of an insufficient mechanical stability and durability. We evaluated the influence on the durability and the ability of degradation of various parameters such as: co-presence of other metals, and the thickness of the oxide layer. The interesting electrocatalytic ability of the manganese oxides combined with the low production of oxy-clorurate species and at low cost, do encourage further research with the aim of improving the stability and durability of these materials by using more efficient preparation techniques.