Evaluation of Absorbent Solutions for the Integrated CO2 Desorption and Electrolysis

Abstract

CO₂ electrolysis is an approach that contributes to mitigating global warming. Integrated CO₂ electrolysis is a possibility to reduce operating costs by combining desorption and electrolysis. In this approach, it is important to provide sufficient CO₂ directly from the absorbent solution to the catalyst, whereby the physically absorbed CO₂ appears to play a central role. Therefore, the absorbent solution used for integrated electrolysis must meet a wide range of requirements, as it needs to supply sufficient CO₂ while being compatible with the process conditions in the cell. In this study, it is demonstrated that KOH and piperazine (PZ) are suitable absorbent solutions for integrated CO₂ electrolysis among the three tested groups of absorbents – namely, inorganic, amines, and physical absorbents. The results reveal that physical absorbents provide the highest amount of accessible CO₂ for electrolysis, whereas inorganic absorbents exhibit the highest compatibility with the membranes. KOH and PZ demonstrate the ability to withstand the electrochemical conditions during CO₂ electrolysis and the capability to produce C₂₊ products during integrated CO₂ electrolysis. These results highlight the critical importance of absorbent selection and demonstrate the feasibility of using KOH as well as amine-based solutions, such as PZ, for integrated CO₂ electrolysis.