Manipulating Selectivity of Electrochemical CO2 Reduction at a Cu–Ag Plasmonic Catalyst

Carbon dioxide (CO₂) can be reduced to prevent the introduction of further CO₂ into the atmosphere, while creating other useful carbon-containing products that can be used in chemical processes or as fuels. Plasmonic cathodes are a promising route for CO₂ reduction because they allow for the reduction of CO₂ at low overpotentials and can help direct selectivity for more complex products under illumination.

To this end, silver-coated copper nanocorals on silver foil were investigated as a plasmonic catalyst for CO₂reduction, and were found to produce many products, with some containing as many as three carbons. Furthermore, the nanocorals not only are more stable under reaction conditions than thin-film silver plasmonic electrodes, they also have a higher absorbance in the visible range, as measured by UV-visible spectrometry. Ultimately, 15 products were identified during CO₂ electrolysis at nanocorals illuminated with 365 nm light (corresponding to the plasmon resonance of Ag); major products (greater that 1% Faradaic efficiency) requiring more than 2 electrons were methane, ethylene, and ethanol. Under illumination and at low overpotentials (-0.6 to -0.8 V_RHE), this catalyst also promoted CO₂ reduction products such as carbon monoxide over hydrogen evolution, the undesired decomposition of the aqueous electrolyte. At overpotentials between -0.8 and -1.0 V_RHE there was an increase in higher carbon products. Taken together, this makes copper–silver nanocorals a very promising catalyst for CO₂ reduction reactions as it increases selectivity for more complex CO₂ reduction products at relatively low overpotentials.

This work was largely supported by the National Science Foundation under Grant No. CBET-1653430. This material is based upon work performed at the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award No. DE-SC0004993. Work at the Molecular Foundry was supported by the Office of Science, Office of Basic Energy Sciences of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.