Catalyst degradation and product selectivity changes
are two of
the key challenges in the electrochemical reduction of CO2on copper electrodes. Yet, these aspects are often overlooked. Here,
we combinein situX-ray spectroscopy,in
situelectron microscopy, andex situcharacterization
techniques to follow the long-term evolution of the catalyst morphology,
electronic structure, surface composition, activity, and product selectivity
of Cu nanosized crystals during the CO2reduction reaction.
We found no changes in the electronic structure of the electrode under
cathodic potentiostatic control over time, nor was there any build-up
of contaminants. In contrast, the electrode morphology is modified
by prolonged CO2electroreduction, which transforms the
initially faceted Cu particles into a rough/rounded structure. In
conjunction with these morphological changes, the current increases
and the selectivity changes from value-added hydrocarbons to less
valuable side reaction products,i.e., hydrogen and
CO. Hence, our results suggest that the stabilization of a faceted
Cu morphology is pivotal for ensuring optimal long-term performance
in the selective reduction of CO2into hydrocarbons and
oxygenated products.