Anion effects govern efficiency of electrochemical amine-mediated CO₂ capture/release.

Abstract

Ambient electrochemical CO₂ capture powered by renewable energy offers a promising carbon removal route, exemplified by the emerging electrochemically mediated amine regeneration (EMAR) process demonstrated in lab-scale single cells and stacks. However, molecular-level insight into EMAR interfacial kinetics is still missing, particularly at the anode, where CO₂ release involves a mechanistically non-trivial re-complexation process at the electrode-electrolyte interface, coupling heterogeneous metal-ion release with bulk complexation. Here, we report the time-resolved characterization of the interfacial molecular processes of the EMAR CO₂ release process. Using in situ Fourier-transform infrared (FTIR) spectroscopy and ultraviolet-visible (UV-vis) spectroscopy, cyclic voltammetry, and real-time differential electrochemical mass spectrometry (DEMS), we examine how the nature of the electrolyte anion affects the CO₂ release onset potentials. The time-resolved analyses reveal that Cl⁻ ions are more effective in releasing Cu ions and hence CO₂ than nitrate or perchlorate. Molecular dynamics simulations show that strong surface Cu-Cl interactions likely facilitate favorable CO₂ and carbamate adsorption kinetics. We expect that this study paves the way for broader use of interfacial in-situ analytics in electrified CO₂ capture and release.