Issue 28, 2024

Deciphering the role of aromatic cations in electrochemical CO2 reduction: interfacial ion assembly governs reaction pathways

Abstract

The accumulation of ions at electrochemical interfaces governs the local chemical environment, which in turn determines the reaction pathways and rates of electrocatalytic processes, including electrochemical CO2 reduction. Imidazolium cations have been shown to promote CO2 reduction in nonaqueous electrolytes, where multiple mechanisms have been proposed for how imidazolium facilitates CO2 reduction. However, many puzzles persist surrounding how imidazolium cations modify local chemical environments at electrochemical interfaces during CO2 reduction. Dialkylimidazolium cations are multifunctional species that interact with adsorbed CO2˙ while also donating protons and forming carbene-mediated coordination complexes. In this work, we exploit the combination of independent proton donor [Et3NH]Cl and aprotic imidazolium cations, namely 1-ethyl-2,3-dimethylimidazolium ([EMMIm]+) and 1-ethyl-2,3,4,5-tetramethylimidazolium ([EM4Im]+) to further illuminate how imidazolium cations promote selective CO2 electrochemical reduction. Our data indicates that the presence of an aromatic, planar delocalized charge region on imidazolium rings plays an essential role in stabilizing CO2˙ to promote electrocatalytic reduction. Kinetic and steady-state electrochemical analysis demonstrates that ring substituents of [EMMIm]+ additionally tune local chemical environments to impact the rate and product distribution of CO2 reduction by limiting the transport of proton donors. Further, we leverage surface-enhanced Raman scattering in the presence of a molecular probe of local electric fields to illustrate that the unique interface-tuning properties of [EMMIm]+ stem from potential-driven assembly at cathodes. Our study highlights how imidazolium substituents can be tuned to regulate interfacial electrochemical environments and illustrates the importance of balancing CO2˙ stabilization and proton transport in sustaining steady-state electrochemical CO2 reduction with high rate and selectivity. More broadly, our results suggest that aromatic cations promote electrochemical CO2 reduction via a distinct “π+–anion” interaction that appears to be the electrostatic analog of the more commonly investigated “cation–π” interaction, which drives self-assembly in proteins and many other biological systems.

Graphical abstract: Deciphering the role of aromatic cations in electrochemical CO2 reduction: interfacial ion assembly governs reaction pathways

Supplementary files

Article information

Article type
Paper
Submitted
26 апр. 2024
Accepted
11 јун. 2024
First published
11 јун. 2024

J. Mater. Chem. A, 2024,12, 17169-17180

Deciphering the role of aromatic cations in electrochemical CO2 reduction: interfacial ion assembly governs reaction pathways

W. Guo, B. Liu, S. R. Anderson, S. G. Johnstone and M. A. Gebbie, J. Mater. Chem. A, 2024, 12, 17169 DOI: 10.1039/D4TA02903H

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements