Dual Mode in situ Monitoring of CO2 Conversion via pH indicator and UV Vis Spectroscopy

The integration of the KHCO 3 fed bipolar membrane (BPM) electrolyzer with KOH based CO 2 capture enables directly in situ conversion of captured CO 2 into valuable carbonaceous products, eliminating costly CO 2 recovery and compression steps. Even this integrated BPM system assembly holds promise, the critical lack of CO 2 adsorption intermediate species tracking necessitates the development of a monitoring platform. This work pioneers a novel dual-modal strategy employing simultaneous indicator-based sensing with in situ UV-Vis spectroscopy, achieving real time visualization of triphasic dynamics during integrated CO 2 capture-regeneration-conversion. Within this synergistic process involving Ar-saturated KHCO 3 decomposition, and electrochemical reduction, an etched indium (In) catalyst achieves 50% formate Faradaic efficiency (FE) at -1.1 V vs. RHE. The synergistic application of these complementary in situ diagnostics unlocks fundamental mechanistic insights into integrated CO 2 capture and conversion systems, establishing them as critical enablers for advancing efficient and scalable electrochemical CO 2 valorization.