Review—High-Pressure Carbon Dioxide Separation Using Ionic Liquids: A CO2-Electrocatalysis Perspective

Abstract

The use of methane as the energy vector in our current energy matrix has challenged scientists to solve problems, which are now related to the exploration of oil wells but tomorrow will be the foundation for a carbon-neutral industry. Subsea exploration challenges engineers to find new solutions to separate CO2 from CH4 at the extremely high pressure of ca. 400 bar, to which all mature separation technologies are unsuitable. In this review, we highlight possible ways to employ ionic liquid (IL) as a highly selective absorbent to CO2 for extremely high pressure. Besides revising the high-pressure physical-chemical properties of ILs, the IL designing principles, and finally, the current employment of IL for preparing membranes, we prospect possible solutions for the sluggish, disfavored IL-regeneration at high pressure. We prospect—CO2 electro-reduction reaction (CO2RR) as a promising disruption for separation processes, being CO2RR-based technologies viable not only for IL-regeneration after the IL-based CO2 capture but also for CO2 conversion into valuable fuels/chemicals. As a prelude to CO2RR-based technologies, this review highlights key aspects concerning the use of IL as the electrolyte in an electrochemical cell performing CO2RR.