Electrochemical Conversion of High Pressure CO2

Abstract

The electrochemical reduction of carbon dioxide (CO2R) via an electrochemical process is a strategic approach aimed at completing the carbon cycle for chemical production. Traditionally, this field has predominantly focused on conducting electrolysis on CO2 under standard atmospheric pressure. However, in industrial applications, CO2 is typically pressurized during its capture, transportation, and storage, often existing in a dissolved state. Our research has unveiled a significant discovery: subjecting aqueous CO2 to a pressure of 50 bar alters the CO2R pathways, favoring the formation of formate. This phenomenon is consistently observed across commonly used CO2R catalysts. Through the development of effective techniques for operating under high pressures, including a measurable Raman spectroscopy approach during the ongoing reaction, we have established a connection between the increased preference for formate and the heightened coverage of CO2 on the cathode surface. This collaboration between theoretical models and experimental data strongly supports this mechanism and has led us to enhance the cathode surface of a copper electrode with a proton-resistant layer. This innovation amplifies the selective impact caused by pressure. Furthermore, our research has unveiled the potential to transform gas-phase high-pressure CO2 into ethylene (C2H4) through CO2R. We conducted density functional theory calculations to identify a range of copper alloys that promote C-C dimerization under high pressure, which represents the rate-limiting step for C2H4 production. The theoretical predictions were validated through a combination of electrochemical measurements and operando observations, guiding us in designing a copper-based catalyst for efficient and active conversion of CO2 to C2H4.