ELECTROCATALYSIS AND AMPEROMETRIC DETECTION USING AN ELECTRODE MADE OF COPPER-OXIDE AND CARBON PASTE

Amperometric flow measurements were made at +0.55 V vs Ag/AgCl in 0.1 M NaOH background electrolyte with Cu2O/C-paste electrodes. Stable and sensitive electrocatalytic responses for oxidations of carbohydrates, amino acids, aliphatic diols, simple alcohols, amines, and alkyl polyethoxy alcohol detergents were observed. Linear responses at low concentrations yielded detection limits in the picomole range. Typical relative standard deviations were 1.2%. Linear plots of 1/l(p) vs 1/C(analyte) indicated Langmuir-type adsorption of analytes on the electrode surface. It was concluded that the active sites could be represented as CuO.OH. CuO, CuCl, and Cu2O were examined as starting materials, and the last was found to be the best. A proposed mechanism for oxidations of these analytes required both hydroxyl radical active sites (CuO.OH) and neighboring adsorbed analyte sites. The rate-determining step involved the formation of a bridged cyclic intermediate and the abstraction of a hydrogen from the alpha-carbon by the adsorbed hydroxyl radical attack.