Energy-Efficient Electrified Ethylene Production from Carbonate Capture Liquid in Reactive Capture System

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Direct air capture (DAC) of CO2 is typically implemented by utilizing alkali hydroxides as capture solutions to form carbonate. However, the release of CO2 and the regeneration of alkali hydroxide require an energy-intensity thermal cycle up to 900 °C. Moreover, the subsequent valorization of gaseous CO2 into products lead to additional energy demands and system complexities. Here, we present a reactive capture system – the integration of CO2 capture with electrochemical upgrade of CO2 into ethylene. We began by seeking to understand the origins of limitations of ethylene production in prior electrochemical reactive capture systems using in-situ Raman spectroscopy. We found that the CO2-starved local reaction environment on catalyst surface leads to dominant hydrogen evolution reaction, outcompeting CO2 electroreduction and suppressing C-C coupling. We therefore developed catalyst strategies to facilitate CO2 activation and promote the cooperative adsorption of key C1 intermediates for enhanced spatial availability of C1-C1 coupling. This was achieved by porous dilute alloy catalyst design and tandem catalysis system optimization. We report a 46% ethylene Faradaic efficiency (FE) with nearly 100% CO2 utilization at 200 mA cm–2 in electrochemical reactive capture system, resulting in a 65 wt% ethylene concentration in the product stream. We achieve a carbonate-to-ethylene system with an overall ethylene energy efficiency of 17% at 200 mA/cm2, which is 1.7-fold higher than the most efficient prior reports in reactive capture systems.