(686d) Binding Site Diversity Promotes CO2 Electroreduction to Ethanol

The electrochemical CO₂ reduction reaction (CO₂RR) to multi-carbon products, such as ethanol and ethylene, offers a way to produce fuels and chemicals from renewable energy. CO₂RR technology is a promising solution to address the intermittency of renewable electricity and, ultimately, enable the realization of renewable fuels.

In CO₂RR to multi-carbon products, ethylene and ethanol share similar reaction intermediates. While an impressive Faradaic efficiency (FE) of 70% for ethylene has been reported, the ethanol FE on pure Cu has remained below 20%.

Recent studies have suggested that the C₂₊ selectivity in CO₂RR on Cu catalysts is site-specific and can be increased via doping and other strategies that modify surface vacancies. Nevertheless, even with this progress, the highest Faradaic efficiencies for ethanol have remained below 30%.

Here we introduce diverse binding sites to a Cu catalyst, an approach that destabilizes the ethylene reaction intermediates and thereby promotes ethanol production. We develop a bimetallic Ag/Cu catalyst that implements the proposed design toward an improved ethanol catalyst. It achieves a record Faradaic Efficiency of 41% to ethanol. It achieves this 250 mA/cm² and -0.67 V vs. RHE, leading to an energy efficiency of 25%. The new catalysts exhibit an in-situ Raman spectrum, in the region associated with CO stretching, that is much broader than that of pure Cu controls, a finding that we account for via the diversity of binding configurations. Controls featuring layered Cu:Ag catalysts, but that fail to exhibit a high areal density of Cu:Ag interfaces at the catalyst surface, do not achieve high ethanol efficiency, and also do not exhibit spectroscopic evidence of binding diversity.

The mechanism that implicates multi-site binding explains the enhanced ethanol production for bimetallic catalysts and presents a new framework to design multi-metallic catalysts to control the reaction path in CO₂ reductions toward desired products.