Electrochemical oxidation of o-aminophenol in aqueous acidic medium: formation of film and soluble products

The electrochemical oxidation of o-aminophenol (OAP) has been studied by cyclic voltammetry on platinum (Pt) and glassy carbon (GC) electrodes. Films formed on Pt exhibited a voltammetric response that is dependent on the final potential applied during the electropolymerization. Although a less electroactive film has been obtained on Pt electrodes cycled at higher potentials, modified GC electrodes showed a well-defined redox response independently of the potential range used. This result is attributed to an activation process of the GC electrode rather than to an electroactive film deposited on the electrode. The deposition process of thin films was also investigated with quartz crystal microbalance experiments. Poly-o-aminophenol (POAP) films were insoluble with an electrochromic response from colorless to brown, and a ladder structure confirmed by infrared spectra. Exhaustive electrolysis of OAP produced a reasonable amount of soluble product, which after solvent extraction, was characterized as 2-aminophenoxazin-3-one (APZ), a product also prepared by chemical oxidation of OAP. A route of electrooxidation of OAP has been proposed based on electrochemical and spectroscopic results.