Understanding the mechanism of supercapacitive carbon dioxide capture through solid-state and in situ NMR Zeke Coady, Dr Zhen Xu, Dr Suzi Pugh, Grace Mapstone, Dr Alexander Forse University of Cambridge, UK Supercapacitive carbon dioxide capture is a promising new technique for concentration of CO 2 from gas mixtures, which offers potentially lower energy consumption than amine scrubbing, and uses inexpensive and environmentally benign components of activated carbon electrodes with aqueous salt electrolyte. (1-3) However, the mechanism of action of these systems is unclear, preventing us from using rational design to improve key metrics including selectivity, absorption capacity, and energy efficiency. The disordered nanostructure of the activated carbon electrodes presents obstacles to understanding how CO2's involvement in supercapacitative charging results in its absorption and desorption. In this work, solid-state NMR is demonstrated as a viable method for the study of supercapacitative carbon dioxide capture. Model supercapacitor electrodes were prepared from different activated carbons and loaded with either carbon-13-enriched HCO 3 - or carbon-13-enriched CO 2 , then analysed through 13 C and 1 H NMR. We can then observe quantitative adsorption of CO 2 and HCO 3 - into our model system as well as exchange between the in-pore and ex-pore environments of the activated carbon. The presence of the activated carbon electrode resulted in a significant enhancement in CO 2 solubility in electrolyte. Studies of absorption of CO 2 in different activated carbons was observed and compared with results of supercapacitive carbon capture experiments, demonstrating that both absorption at neutral charge and improved exchange between the in-pore and ex-pore environment correlate with improved CO 2 capture activity. These findings provide insight into the mechanism of supercapacitive carbon capture and into differences in activity between different activated carbons. References 1. Kokoszka, B.; Jarrah, N. K.; Liu, C.; Moore, D. T.; Landskron, K. Supercapacitive Swing Adsorption of Carbon Dioxide. Angewandte Chemie International Edition 2014 , 53 (14), 3698–3701. https://doi.org/10.1002/anie.201310308. 2. Bilal, M.; Li, J.; Guo, H.; Landskron, K. High-Voltage Supercapacitive Swing Adsorption of Carbon Dioxide. Small n/a (n/a), 2207834. https://doi.org/10.1002/smll.202207834. 3. Binford, T. B.; Mapstone, G.; Temprano, I.; Forse, A. C. Enhancing the Capacity of Supercapacitive Swing Adsorption CO2 Capture by Tuning Charging Protocols. Nanoscale 2022 , 14 , 7980–7984. https://doi.org/10.1039/D2NR00748G.
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