Lead underpotential deposition for the surface characterization of silver ad-atom modified gold electrocatalysts for glucose oxidation

The surface composition of Ag-Au electrocatalysts plays an important role in enhancing their activity for glucose oxidation. In this work, the surface of a polycrystalline Au electrode was modified through underpotential deposition of Ag (Ag-upd) and the surface composition of the resulting Ag-upd-modified Au catalysts was characterized using an ex situ electrochemical technique involving underpotentially deposited lead (Pb-upd). Recognizing that Ag and Au surfaces exhibit distinct Pb-upd charge densities, the Pb-upd charge density associated with a Ag ad-atom modified Au electrode surface is a representation of its surface composition. This enables quantification of the Ag and Au fractional surface coverages, which are in good agreement with those predicted based on the Ag-upd charge density passed during Ag-upd-Au surface preparation. The dependence of the glucose oxidation Kinetics on the surface composition of the Ag-upd-Au catalyst was investigated using voltammetry. Optimal catalytic activity was provided by catalysts with 56% Ag-upd coverage. Our investigation, while providing a reliable analytical technique (using Pb-upd) for compositional characterization of heterogeneous catalyst surfaces, supports the surface composition dependence of the activity of Ag-upd-Au catalysts toward glucose oxidation. (C) 2017 Elsevier B.V. All rights reserved.