Supercapacitor-Based CO2 Capture Enhanced by Electrolyte pH Control

Abstract

Supercapacitive swing adsorption (SSA) is emerging as an energy-efficient alternative to traditional thermally-driven CO 2 capture technologies. While a range of operational factors have been actively explored to increase understanding of this technology, SSA is currently limited by low rates of CO 2 capture. In this work, we investigate how electrochemical CO 2 capture responds to changes in electrolyte pH by combining galvanostatic CO 2 adsorption measurements with quantitative solid-state 13 C-NMR spectroscopy. Our measurements reveal 30% higher adsorption rates for basic electrolytes compared to neutral electrolytes. In contrast, in acidic electrolyte, we see substantially lower adsorption rates and capacities. To probe the origin of these observations, we use 13 C NMR spectroscopy on uncharged electrolyte-soaked electrodes to examine CO 2 speciation. While dissolved CO 2 is detected across all electrolytes, bicarbonate concentrations increase with increasing electrolyte pH, suggesting a bicarbonatedriven or pH-swing driven mechanism of action. Overall, our study provides additional insights into the factors governing CO 2 capture in SSA by highlighting the role of CO 2 speciation and electrolyte pH in optimizing device performance.