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 (Agupd) and the surface composition of the resulting Agupd-modified Au catalysts was characterized using an ex situ electrochemical technique involving underpotentially deposited lead (Pbupd). Recognizing that Ag and Au surfaces exhibit distinct Pbupd charge densities, the Pbupd 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 Agupd charge density passed during Agupd-Au surface preparation. The dependence of the glucose oxidation kinetics on the surface composition of the Agupd-Au catalyst was investigated using voltammetry. Optimal catalytic activity was provided by catalysts with 56% Agupd coverage. Our investigation, while providing a reliable analytical technique (using Pbupd) for compositional characterization of heterogeneous catalyst surfaces, supports the surface composition dependence of the activity of Agupd-Au catalysts toward glucose oxidation.