(301e) Electrochemically-Mediated Carbon Dioxide Separation Using Redox-Active Molecular Sorbents and Process Intensification

Anthropogenic carbon dioxide emissions present a serious challenge to our society. One of the foremost mitigation strategies involves carbon capture, particularly from large stationary emission sources, followed by sequestration or utilization. The incumbent technology for carbon dioxide separation is temperature-swing-based amine scrubbing, which can be challenged by the substantial energy demand, sorbent degradation, environmental concerns and large footprint. Electrochemically-mediated separations offer a low-temperature, ambient-pressure alternative for carbon capture, representing a promising yet largely unchartered research area. By being electrically driven, these systems can be controlled precisely to reduce energy losses, are modular and thus easy to implement, and possess great adaptability to the multi-scale nature of carbon capture.

In this talk, an electrochemically-mediated carbon capture technique will be introduced, relying on redox-active quinoid species that undergo significant changes in their carbon dioxide binding affinity as they progress through an electrochemical cycle. Though the observation of reversible carbon dioxide binding by quinones has been made before, such chemistry can only be operated using flammable, toxic aprotic solvent, posing a great barrier toward large-scale implementation.

Here, we demonstrate that rationally designed aqueous electrolytes with high salt concentration can effectively resolve the incompatibility between aqueous environments and quinone electrochemistry for carbon capture. The salt-concentrated aqueous media offer distinct advantages including extended electrochemical window, high carbon dioxide activity, significantly reduced evaporative loss and material dissolution, and importantly, greatly suppressed competing reactions as verified by both experiments and theoretical calculations. When tested using simulated flue gas, our proposed system achieved outstanding performance metrics (capacity, stability, efficiency and electrokinetics) and competitive system energetics, advancing electrochemical carbon separation further towards practical applications. Moreover, through integration with a novel electrochemically-controlled gas-gating membrane that dynamically controls gas passage, an effectively continuous operation of carbon capture and release can be achieved, bringing new opportunities for process intensification.