To facilitate in situ tests using fluorescence signatures as a quantification method for the species, we proceeded by developing a custom-designed optically transparent microfluidic electrochemical flow cell inspired from microfluidic chips that can be integrated into a fluorescence microscope and is compatible with optical imaging, as shown in Figure . The cell connects to a potentiostat for electrochemical control and acquisition and is designed with inlets/outlets for electrolyte flow into external reservoir. The cell structure includes an anion exchange membrane (DSV-N) sandwiched between two 5 by 10 mm Avcarb190 porous carbon electrodes layered in pocket molded within Polydimethylsiloxane (PDMS) half cells and two acrylic end plates for compression. The half-cell has a thickness of 8 mm, suitable for direct observation with a 10x/0.3NA Leica objective (556503) with a working distance of 11 mm mounted on a confocal microscope (Leica DMi8 body with Andor dragonfly spinning disk). The unprecedented resulting transverse resolution for local electrochemical characterization in porous electrode with this objective was 1 𝜇𝑚 per pixel and about 25𝜇𝑚 for the depth of field. Peristaltic pumps were employed for circulating the electrolyte, and the headspace on the negolyte side could be switched from N2 to CO2 during the experiments. Figure displays the Widefield image of the porous electrode extracted from this cell, while Figure provides a schematic representation of the experimental setup (further details can be found in SI section 4.3, Figures and). To investigate the potential correlation between fluorescence intensity at wavelengths identified by the ex situ study and the adduct concentration, we designed an experiment wherein the battery is initially charged under N2, followed by the introduction of CO2. operation of the described microfluidic cell under the fluorescent microscope, where two channels with different excitation/absorption settings were established for monitoring. In alignment with our ex situ data, channel 1 was configured with an excitation wavelength of 488 nm and an emission wavelength peaking at 594 nm, corresponding to the reduced form of 1,5-BTMAPAQ. Meanwhile, channel 2 was set up with an excitation wavelength of 405 nm and an emission wavelength peaking at 521 nm, corresponding to the adduct form of 1,5-BTMAPAQ. At the initial time point (t0=0), no fluorescence is evident, consistent with the ex-situ data, attributed to the oxidized compound not fluorescing within the chosen wavelengths. As the charging process begins and progresses under a nitrogen atmosphere, the reduced form becomes fluorescent (channel 1, t1 = 2894.5 s), with intensity increasing alongside the charging capacity. During this period, there is a minor change in the fluorescence intensity of channel 2, as expected due to the absence of any adduct species. Note that the pH of the solution swings up, given that the reaction is protoncoupled. At the end of the charge, the nitrogen headspace is switched to 1 bar CO2 to initiate the carbon capture process. Subsequent purging of CO2 induces the conversion of the reduced form to the CO2quinone adduct, resulting in the loss of fluorescence in channel 1. Intriguingly, channel 2, characterized by a distinct fluorescence signal from the adduct, becomes intense. Note that as the carbon dioxide is purged, the pH drops to 7 because the hydroxides are being utilized for bicarbonate/carbonate formation in parallel with the adduct formation. Upon discharging, the fluorescence gradually fades (t3 = 4140.5).