In Situ Techniques for Quinone-Mediated Electrochemical Carbon Capture and Release in Aqueous Environments

We present two novel experimental techniques designed to quantify the contributions of nucleophilicity-swing and pH-swing mechanisms to carbon capture in the electrochemical aqueous quinone-based CO2 capture process. Through thermodynamic analysis, we elucidate the intricate interplay between these two mechanisms, and emphasize the critical role of understanding this interplay in the material discovery cycle for carbon capture applications. This insight prompts the development of two innovative in situ techniques. The first technique capitalizes on discernible voltage signature differences between quinone, and quinone-CO2 adducts. By incorporating a reference electrode into the carbon capture cell setup, we apply this method to investigate bis[3-(trimethylammonio)propyl]-anthraquinones (BTMAPAQs). Our findings reveal the isolated contributions of nucleophilicity-swing and pH-swing mechanisms to overall carbon capture capacity under varying wait times and CO2 partial pressures. The second method is developed based on our finding that the adduct form of the quinone exhibits a fluorescence emission from an incident light at wavelengths distinct from the fluorescence of the reduced form, enabling differentiation through optical band-pass filtering at each unique fluorescent signature. Thus, we introduce a non-invasive, in situ approach using fluorescence microscopy, providing the unique capability to distinguish between oxidized, reduced, and adduct species with sub-second time resolution at single digit micrometer resolution. This powerful technique holds significant promise for studying such systems, representing an advancement in our ability to understand carbon capture processes.