Energy Efficient Carbon Capture through Electrochemical pH Swing Regeneration of Amine Solution

Mu Lin; Clément Ehret; Hubertus V M Hamelers; Annemiek Ter Heijne; Philipp Kuntke

doi:10.1021/acssuschemeng.3c08430

Energy Efficient Carbon Capture through Electrochemical pH Swing Regeneration of Amine Solution

ACS Sustain Chem Eng. 2024 Apr 30;12(19):7309-7317. doi: 10.1021/acssuschemeng.3c08430. eCollection 2024 May 13.

Authors

Mu Lin^{1

2}, Clément Ehret¹, Hubertus V M Hamelers^{1

2}, Annemiek Ter Heijne^{1

2}, Philipp Kuntke^{1

2}

Affiliations

¹ Wetsus, European Centre of Excellence for Sustainable Water Technology, P.O. Box 1113, 8900CC Leeuwarden, The Netherlands.
² Environmental Technology, Wageningen University, P.O. Box 17, 6700 AA Wageningen, The Netherlands.

Abstract

Carbon capture is widely acknowledged as a promising strategy for achieving negative emissions. Electrochemical carbon capture technologies are considered a viable alternative to conventional temperature swing processes. Among these, employing the hydrogen oxidation and hydrogen evolution reactions as a redox couple, along with an ion exchange membrane, offers an effective means of establishing a pH swing for desorbing CO₂ and regenerating the alkaline solvent. However, the practical scalability of this approach is impeded by challenges such as high energy demands resulting from a high pH differential between anodic and cathodic environments and operation with solutions with a low conductivity, required to obtain an acceptable current yield. To address these limitations, this study introduces an innovative anion exchange membrane (AEM)-based electrochemical process for solvent regeneration. Our research demonstrates the advantageous utilization of amines as chemical buffers. Selecting an amine solution with a favorable pK_a (∼7 to 10) helps in maintaining bicarbonate as the predominant carbon species within the system, thereby ensuring a high current yield (>80%) across various operational conditions (current, load ratio, and solution concentration). Furthermore, our analysis indicates that the use of amine solutions effectively reduces the overpotential of the hydrogen evolution reaction due to a lower local pH. This results in a minimum energy requirement of 63 kJ/mol at a current density of 20 A/m² to regenerate the solution (MDEA) while maintaining high (>99%) product (CO₂) purity.