Direct Oxygen-containing Simulated Flue Gas Electrolysis to Multi-carbon Products with High Efficiency

Electrocatalytic CO2 reduction reaction (CO2RR) to value-added multi-carbon (C2+) products provides an attractive path for storing intermittent renewables. However, the process typically requires high-purity CO2 as a feedstock, which undermines its economic viability and practical feasibility.Direct utilization of flue gas for CO2RR (i.e. direct flue gas electrolysis) in acidic media is a promising strategy to reduce operating expenses by eliminating the need for energy-intensive CO2 separation and purification from flue gas and to address the CO2 loss issue arising from alkaline/neutral media. The challenge of direct flue gas electrolysis, though, lies in selectively facilitating CO2RR to C2+ products while simultaneously suppressing the competing hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) favored thermodynamically, owing to the low CO2 concentration and the presence of O2 impurities in flue gas.In this project, leveraging our prior research experience in CO2RR-related catalyst design and reaction engineering, based on O2-containing simulated flue gas feeds, we aim to address the aforementioned challenge in direct flue gas electrolysis through integrating catalyst design and system development. On the one hand, we will develop a cation exchange membrane (CEM) based acidic membrane electrode assembly (MEA) electrolysis system for direct O2-containing simulated flue gas electrolysis to C2+ products. On the other hand, we aim to develop molecule-modified Cu-based catalysts to improve C2+ selectivity at high current densities, CO2 utilization efficiency, and stability simultaneously under CEM-based acidic MEA system in direct O2-containing simulated flue gas electrolysis. Our preliminary results show that 3,5-diamino-1,2,4-triazole molecule-modified Cu catalysts deliver a high C2+ selectivity of 50% at 200 mA cm-2 in the proof-of-concept CEM-based acidic MEA system, suggesting that moleculemodified catalysts integrated with a CEM-based acidic MEA system are promising to promote CO2-to-C2+ from O2-containing simulated flue gas. Lastly, by uniting in situ/operando spectroscopic characterization techniques with theoretical calculations, we will establish the structure-property relations of molecule-modified Cu-based catalysts towards direct O2-containing simulated flue gas electrolysis to C2+ products. The successful implementation of this project will generate crucial knowledge for designing high-efficiency CO2-to-C2+ electrocatalysts using O2-containing simulated flue gas. This work will advance the development of direct flue gas electrolysis technology, facilitating its future practical applications and contributing to Hong Kong’s goal of achieving carbon neutrality by 2050.