The surface structure and oxide content near the surface of copper electrodes under CO and CO 2 reduction conditions are debated. By live-monitoring Cu and Cu 2 O Bragg peaks from the surface of a polycrystalline Cu electrode while scanning from open-circuit potential to CO reduction potentials, we show that the near-surface region is fully converted to the metallic phase at approximately +0.3 V vs RHE.

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Single and polycrystalline Cu electrodes serve as model systems for the study of the electroreduction of CO , CO and nitrate, or for corrosion studies; even so, there are very few reports combining electrochemical measurements with structural characterization. Herein both the electrochemical properties of polycrystalline Cu and single crystal Cu(1 0 0) electrodes in alkaline solutions (0.1 m KOH and 0.1 m NaOH) are investigated. It is demonstrated that the pre-treatment of the electrodes plays a crucial role in determining their electrochemical properties. Scanning tunneling microscopy, X-ray photoelectron spectroscopy and cyclic voltammetry are performed on Cu(1 0 0) electrodes prepared under UHV conditions; it is shown that the electrochemical properties of these atomically well-defined electrodes are distinct from electrodes prepared by other methods. Also highlighted is the significant role of residual oxygen and electrolyte convection in influencing the electrochemical properties.

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Establishing relationships between the surface atomic structure and activity of Cu-based electrocatalysts for CO 2 and CO reduction is hindered by probable surface restructuring under working conditions. Insights into these structural evolutions are scarce as techniques for monitoring the surface facets in conventional experimental designs are lacking. To directly correlate surface reconstructions to changes in selectivity or activity, the development of surface-sensitive, electrochemical probes is highly desirable. Here, we report the underpotential deposition of lead over three low index Cu single crystals in alkaline media, the preferred electrolyte for CO reduction studies. We find that underpotential deposition of Pb onto these facets occurs at distinct potentials, and we use these benchmarks to probe the predominant facet of polycrystalline Cu electrodes in situ. Finally, we demonstrate that Cu and Pb form an irreversible surface alloy during underpotential deposition, which limits this method to investigating the surface atomic structure after reaction.