New insights into the electrochemical reduction of carbon dioxide on metallic copper surfaces

TLDR

The study presents new insights into CO₂ electroreduction on metallic copper, enabled by a highly sensitive experimental methodology for product identification and quantification. A custom electrochemical cell coupled to gas chromatography and nuclear magnetic resonance was used to maximize product concentrations, and analysis of C1–C3 product identities and turnover frequencies yielded mechanistic information. The authors identified 16 CO₂ reduction products, including five novel ones, and proposed an enol‑like surface intermediate pathway that explains the selectivity for eleven distinct C₂⁺ oxygenated products.

Abstract

We report new insights into the electrochemical reduction of CO2 on a metallic copper surface, enabled by the development of an experimental methodology with unprecedented sensitivity for the identification and quantification of CO2 electroreduction products. This involves a custom electrochemical cell designed to maximize product concentrations coupled to gas chromatography and nuclear magnetic resonance for the identification and quantification of gas and liquid products, respectively. We studied copper across a range of potentials and observed a total of 16 different CO2 reduction products, five of which are reported here for the first time, thus providing the most complete view of the reaction chemistry reported to date. Taking into account the chemical identities of the wide range of C1–C3 products generated and the potential-dependence of their turnover frequencies, mechanistic information is deduced. We discuss a scheme for the formation of multicarbon products involving enol-like surface intermediates as a possible pathway, accounting for the observed selectivity for eleven distinct C2+ oxygenated products including aldehydes, ketones, alcohols, and carboxylic acids.