(732a) Electrochemical Control of the CO2 Capture Capacity of Amine Sorbents Using Cu (II)/Cu (I) Redox Chemistry

The most mature carbon capture technology, amine scrubbing, has been beneficial in reducing emissions from fossil fuel combustion. However, the inefficiencies of its thermal regeneration cycle lead to prohibitively high energy consumption. Since the high energy demand largely comes from the thermal capture/release cycle, alternative approaches to cycling are of interest.

One alternative is to use more efficient electrochemical cycles to switch between high capacity CO₂ capture states and low capacity sorbent regeneration states. In this study, the copper (II)/copper (I) redox couple is used to control the CO₂ capacity of the model sorbent 1,2-dimehtylimidazole in water. By alternating between oxidizing and reducing potentials, the solution changes between its 4-coordinate Cu (II) state and its 2-coordinate Cu (I) state. As a result, the redox reaction is coupled with the release or uptake of two sorbent molecules per copper, leading to an increase or decrease in CO₂ capture capacity, respectively.

Experimental results validate this approach, showing that for a given partial pressure of CO₂, the reduced Cu (I) state has a higher CO₂ capacity than the oxidized Cu (II) state. Energy consumption of a full oxidation-reduction cycle is measured using a bench-scale electrochemical cell. The aqueous inorganic carbon concentration agrees with predicted results based on chemical equilibrium calculations, allowing further computational investigation of the effects of solution composition, sorbent equilibrium constants, and inlet CO₂. Through these simulations, we have gained insights into the underlying mechanism, allowing identification of what characteristics the ideal sorbent molecule should have for this application.