Thermodynamic and Economic Assessments of Electrochemical CO₂ Conversion to Dimethyl Ether: Trade-off between Hydrogen Gas and Water Vapor as a Proton Source

Abstract

Electrochemical conversion of carbon dioxide (CO2) to valuable products could provide a transformative pathway to produce renewable fuels while adding value to the CO2 captured at point sources. Here, we investigate the thermodynamic feasibility and economic viability of the electrochemical CO2 reduction reaction to various carbon-containing fuels. In particular, we explore various pathways for conversion of CO2 to dimethyl ether (DME), liquid propane gas, and renewable natural gas. We compare and contrast the use of two different proton sources, including hydrogen gas and water vapor at the anode, on the capital and operating costs (OPEX) of electrochemical systems to produce DME. The results indicate that the electrical costs are the most significant portion of OPEX, demonstrating costs of 0.2–0.6 $/kWh per metric ton of DME. DME production using carbon monoxide and formic acid as intermediates proved to be the most cost-effective, demonstrating levelized costs of energy of 0.28 $/kWh with over 0.15 $/kWh of cost recovery possible through renewable hydrogen tax credits and oxygen and hydrogen gas recovery.