Electrocatalytic reactions of phenolic compounds at ferric ion co-doped SnO2:Sb5+ electrodes

Abstract

The anodic voltammetric responses for some phenolic compounds (phenol, p-chlorophenol, p-nitrophenol, p-aminophenol, p-methoxyphenol and hydroquinone) can be significantly enhanced at the Sb5+ and Fe3+ co-doped SnO2 electrodes as compared to those at the Sb5+ doped SnO2 electrodes. Tin dioxide based electrodes, Sb5+ and smaller amounts of Fe3+ ion co-doped SnO2 electrodes, are prepared on Ti substrates by a thermal decomposition method from the chloride sol. The electrocatalytic activities of SnO2:Sb5+,Fe3+ electrodes are sensitive to the content of the co-doped Fe3+ ion as well as that of Sb5+ion, and the maximum activity for the anodic oxidation of phenolic compounds has been found at the SnO2:Sb5+(5%),Fe3+(0.5%) electrode. The larger response at the SnO2:Sb5+(5%),Fe3+(0.5%) electrode is demonstrated to result from increased values of the apparent heterogeneous rate constants (kapp) for the corresponding anodic reactions at the electrode surfaces, which is caused by the enhanced adsorption of the phenolic compounds at Sb-sites at the electrode surface via the non-bonded electron pairs of the hydroxyl group in acidic media. The electrocatalytic benefit of the SnO2:Sb5+(5%),Fe3+(0.5%) electrode is anticipated to be a result of the increased number of Sb5+ sites in the lattices due to the charge compensation by Fe3+ ion.