Cu+ transient species mediate Cu catalyst reconstruction during CO2 electroreduction

Understanding metal surface reconstruction during operation is of the uttermost importance in heterogeneous catalysis as it directly affects the available active sites. However, surface reconstruction is notoriously difficult to study because of the dynamic nature of the phenomena behind it. Here, we report on the mechanism and the intermediates, which drive the rearrangement of copper catalysts during the electrochemical CO2 reduction reaction. In-situ methods, including mass spectrometry and fluorescence spectroscopy, evidence a dissolution – redeposition process mediated by transient species containing copper in +1 oxidation state. Theory identifies copper-adsorbate complexes which form in solution under operating conditions. Copper carbonyls and oxalates emerge as the major reaction-specific species driving copper reconstruction. This work motivates future studies to specifically target these compounds to improve the catalyst operational stability in the electrochemical CO2 reduction reaction.