A redox-active polymeric network facilitates electrified reactive-capture electrosynthesis to multi-carbon products from dilute CO₂-containing streams.

Abstract

Reactive capture - the integration of CO₂ capture with electrochemical upgrade - offers the prospect of improving overall energy efficiency in captured-CO₂-to-fuels by eliminating the gas-phase CO₂ desorption step, and by further offering a CO₂-free gas product stream. Two related challenges limit the potential impact of electrified reactive capture today: its propensity to produce lower-value C₁ products (carbon products containing one carbon atom per molecule); and its failure to retain performance when fed dilute streams (e.g. ~1-10% CO₂). We posit that these could be addressed using catalysts that locally concentrate and activate in-situ generated CO₂: we integrate a redox-active polymeric network whose polymer fragments undergo reversible reduction during the electrochemical conversion process, enabling electron transfer to CO₂ molecules generated in-situ from carbonate capture liquid. We report as a result a 55 ± 5% C₂₊ (carbon products containing two or more carbon atoms per molecule) Faradaic efficiency (FE) at 300 mA/cm² in an electrochemical reactive capture system in which the electrolysis stage is fed with 1 M K₂CO₃. We obtain 56 ± 4 wt% C₂H₄ in the product gas stream. When we use a dilute stream consisting of 1% CO₂ in N₂ at the KOH capture stage, we retain the C₂₊ FE to within 85% (relative) of its value achieved in the case of pure CO₂.