Electrocatalytic Behaviour of Epitaxial Ag(111) Overlayers Electrodeposited onto Noble Metals: Electrooxidation of d-Glucose

The electrooxidation of d-glucose in 0.1 M NaOH has been studied at epitaxially grown Ag monolayers, which have been fabricated by electrodeposition onto Au(111), Pt(111), and Pd(111) single-crystal electrodes. The electrochemical behaviour and the adsorption properties of these Ag monolayers are significantly altered by the underlying substrates. While the Ag monolayer on Pt(111) shows the most negative onset potential for glucose oxidation, Ag overlayers on Au(111) reveal the highest current densities for the systems under study. Interestingly, a Ag submonolayer on Au(111) shows the highest current densities for glucose oxidation under the experimental conditions. However, Ag overlayers on Au(111) with a thickness of two monolayers and more are poor electrocatalysts like massive Ag(111). The influence of OH adsorption and the relevance of the potentials of zero charge for the various Ag surfaces on the measured oxidation current densities are discussed.