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

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.