Electrocatalytic upcycling of high-pressure captured CO2

Abstract

Electrochemical upcycling of captured CO2 – typically under high pressure – holds significant potential to bridge between CO2 emissions and hydrocarbon commodities. However, this conceptual CO2 value chain is yet to be demonstrated. Here, we showcase the valorization of gas-phase high-pressure captured CO2 (HP-cCO2) into ethylene (C2H4) through electrochemical CO2 reduction (CO2R). Guided by theoretical calculations, we devise a single-atom In alloyed Cu catalyst (In1/Cu), which, when integrated into a custom-built high-pressure membrane electrode assembly (MEA) under 20 bar, affords up to 85% Faradaic efficiency (FE) and up to 750 mA cm−2 partial current density toward C2H4. The interplay of theory and high-pressure operando methods links the exceptional performance to the pressure-modulated adsorption configuration of the *CO intermediate, and the elevated CO2 coverage. We also reveal the pivotal role of pressure in mitigating the salt precipitation – a long-standing challenge in the field – by relocating the bicarbonate formation to the catalyst-membrane interface. This was agreed upon by C2H4 FE that is sustained above 80% for 1,500 hours at 600 mA cm−2 under 20 bar. This proof-of-concept, by electrochemically producing C2H4 from HP-cCO2 and re-capturing the residue CO2, delivers industrial grade 99.9% purity C2H4 and exhibits prospect of turning the otherwise costly CO2 capture process into a profit. Energy analysis suggested that directly valorizing HP-cCO2, instead of depressurizing it to accommodate conventional ambient-pressure CO2R and repressurizing the effluents for gas product separation, is essential to minimize the energy consumption.