Issue 9, 2022

The mechanism for acetate formation in electrochemical CO(2) reduction on Cu: selectivity with potential, pH, and nanostructuring

Abstract

Nanostructured Cu catalysts have increased the selectivities and geometric activities for high value C–C coupled (C2) products (ethylene, ethanol, and acetate) in the electrochemical CO(2) reduction reaction (CO(2)RR). The selectivity among the high-value C2 products is also altered, where for instance the yield of acetate increases with alkalinity and is dependent on the catalyst morphology. The reaction mechanisms behind the selectivity towards acetate vs. other C2 products remain controversial. In this work, we elucidate the reaction mechanism for acetate formation by using ab initio simulations, a coupled kinetic-transport model, and loading dependent experiments. We find that trends in acetate selectivity can be rationalized from variations in electrolyte pH and the local mass transport properties of the catalyst and not from changes in Cu's intrinsic activity. The selectivity mechanism originates from the transport of ketene, a stable (closed shell) intermediate, away from the catalyst surface into solution where it reacts to form acetate. While this type of mechanism has not yet been discussed in the CO(2)RR, variants of it may explain similar selectivity fluctuations observed for other stable intermediates like CO and acetaldehyde. Our proposed mechanism suggests that acetate selectivity increases with increasing pH, decreasing catalyst roughness and significantly varies with the applied potential.

Graphical abstract: The mechanism for acetate formation in electrochemical CO(2) reduction on Cu: selectivity with potential, pH, and nanostructuring

Supplementary files

Article information

Article type
Paper
Submitted
08 May 2022
Accepted
01 Aug 2022
First published
03 Aug 2022
This article is Open Access
Creative Commons BY license

Energy Environ. Sci., 2022,15, 3978-3990

The mechanism for acetate formation in electrochemical CO(2) reduction on Cu: selectivity with potential, pH, and nanostructuring

H. H. Heenen, H. Shin, G. Kastlunger, S. Overa, J. A. Gauthier, F. Jiao and K. Chan, Energy Environ. Sci., 2022, 15, 3978 DOI: 10.1039/D2EE01485H

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