Electrocatalytic reactions of phenolic compounds at ferric ion co-doped SnO 2:Sb 5+ 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 Sb 5+ and Fe 3+ co-doped SnO 2 electrodes as compared to those at the Sb 5+ doped SnO 2 electrodes. Tin dioxide based electrodes, Sb 5+ and smaller amounts of Fe 3+ ion co-doped SnO 2 electrodes, are prepared on Ti substrates by a thermal decomposition method from the chloride sol. The electrocatalytic activities of SnO 2:Sb 5+,Fe 3+ electrodes are sensitive to the content of the co-doped Fe 3+ ion as well as that of Sb 5+ion, and the maximum activity for the anodic oxidation of phenolic compounds has been found at the SnO 2:Sb 5+(5%),Fe 3+(0.5%) electrode. The larger response at the SnO 2:Sb 5+(5%),Fe 3+(0.5%) electrode is demonstrated to result from increased values of the apparent heterogeneous rate constants ( k app) 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 SnO 2:Sb 5+(5%),Fe 3+(0.5%) electrode is anticipated to be a result of the increased number of Sb 5+ sites in the lattices due to the charge compensation by Fe 3+ ion.