Electrochemical oxidation of CO on Cu single crystals under alkaline conditions

TL;DR

This study combines experimental and theoretical methods to demonstrate that copper single crystals efficiently catalyze CO oxidation under alkaline conditions, outperforming gold with lower overpotentials due to favorable *OH and *CO-*OH interactions.

Contribution

It provides new insights into the catalytic activity of copper surfaces for CO oxidation, highlighting the role of *OH adsorption and surface structure in lowering overpotentials.

Findings

Cu surfaces show CO oxidation activity at low potentials (0.03-0.14 V).

Cu has lower overpotentials than gold for CO oxidation.

Cu(100) facet exhibits the lowest overpotential among studied facets.

Abstract

We perform a joint experimental-theoretical study of the electrochemical oxidation of CO on copper (Cu) under alkaline conditions. Using cyclic voltammetry on Cu single crystal surfaces, we demonstrate that both Cu terraces and steps show CO oxidation activity at potentials just slightly positive (0.03-0.14 V) of the thermodynamic equilibrium potential. The overpotentials are 0.23-0.12 V lower than that of gold (approx. 0.26 V), which up until now has been considered to be the most active catalyst for this process. Our theoretical calculations suggest that Cu's activity arises from the advantageous combination of simultaneous *OH adsorption under CO oxidation potentials and surmountable *CO-*OH coupling barriers. Experimentally observed onset potentials are in agreement with the computed onsets of *OH adsorption. We furthermore show that the onsets of *OH adsorption on steps are more affected by *CO-*OH interactions than on terraces due to a stronger competitive adsorption. Overall, Cu(100) shows the lowest overpotential (0.03 V) of the facets considered.