Electrocatalytic properties of Au(h k l) electrodes towards oxidation of ethanol in alkaline media

In alkaline media, the mechanism of the oxidation of ethanol on gold single crystal electrodes was investigated over a range of OH^- and ethanol concentrations using cyclic voltammetry. The influence of crystallographic orientation and the role of OH^- on the oxidation of ethanol were suggested. The electrocatalytic activity for ethanol oxidation was increased with increasing OH^- concentration in the solution and/or higher OH^- coverage on the electrode surface. The kinetic parameters such as Tafel slope and reaction orders in respect to OH^- and ethanol were determined. Two Tafel slopes were observed during ethanol oxidation on gold in alkaline media. At low potentials, the Tafel slope was found to be close to 120 mV dec^-1, whereas the high Tafel slope over 300 mV dec^-1 at high potentials, indicating the increasing the surface oxide coverage on the gold electrodes. The reaction orders with respect to OH^- was found to be potential-dependent and involved in the rate determining step.