Surface characterization of copper electrocatalysts by lead underpotential deposition

Abstract

Cu electrodes are model catalysts for a wide variety of interesting energy conversion reactions. Structure sensitivity typically plays an important role in the mechanism of different electrocatalytic reactions. However, quantifying the presence of different domains on Cu electrocatalysts remains a challenge. Herein, we evaluate the lead (Pb) underpotential deposition (UPD) on well-defined Cu electrode surfaces in presence of chloride, as a tool to analyse the surface state and determine the presence and distribution of domains on Cu catalysts. A polycrystalline Cu electrode was specifically modified by applying different electrochemical pre-treatments. Then, its surface ordering was tested by Pb UPD. Results were also compared with well-defined Cu single crystalline electrodes, to estimate the ratio between 〈1 0 0〉, 〈1 1 1〉 facets and defects on the pre-treated Cu electrode. The voltammetric profile of Pb UPD is strongly sensitive to the changes in the structure of the Cu electrode, allowing to monitor the appearance of new defects and domains. We highlight that Pb UPD can be used to provide the electrochemical fingerprint of Cu catalysts and decouple the contribution of different facets and defects in the surface structure.