Among the most widely studied monometallic materials, copper is unique. When used as an electrocatalyst, copper can convert CO2 or CO2-dervied CO to high-value multi-carbon products with appreciable selectivities, such as ethanol and ethylene, that cannot be achieved with other materials.
Although significant works including single-crystal studies, spectroscopic investigations, and computation works have been devoted to understand why copper is so unique, a majority of these more fundamental studies are typically conducted in batch electrochemical reactors that operate at reaction rates (few tens of mA cm-2) far below what is commercially relevant (>100 mA cm-2). This presents a gap between more fundamental works and device-level studies, and little is known about how copper behaves at commercially relevant rates of reaction.
In efforts to address this issue, we sought out to design well-defined nanostructured copper catalysts that selectivity exposed different copper surfaces (e.g. facets), as different atomic arrangements can coordinate and bind to reaction intermediates differently, potentially changing product selectivity.
With these nanostructured catalysts, we can therefore study CO2/CO reduction in a flow-cell electrochemical reactor at high rates that could not previously be achieved, allowing for a potentially deeper understanding of multi-carbon product formation on copper-catalyzed CO2/CO reduction. In particular, copper nanosheets that selectively expose the (111) facets were found to be highly selective toward acetate formation.
An acetate Faradaic efficiency of ~48% and an acetate partial current density of 131 mA cm-2 were achieved in an alkaline environment, the highest reported to date toward acetate formation. Further analysis suggests that the improved acetate formation is due to the suppression of ethylene and ethanol formation as a result of the reduction of (100) and (110) surfaces, respectively.
To learn more about this research, click the link to read the paper: https://www.nature.com/articles/s41929-019-0269-8