In-Operando Observation of Cs + and H2O Distribution Across MEA Figure shows the operando characterization setup for the zero-gap electrolyzer, where the WAXS, XRF and gas chromatography (GC) are coupled to simultaneously measure the MEA signal changes and gas product distribution during CO2 electrolysis. In detail, the analysis of the Bragg peaks from WAXS offers insight into the structural composition of materials. A vertical scan of WAXS measurement (Figure ,B) provides information on the identification of different species within the entire MEA. Figure shows the WAXS spectra of the anode and cathode catalyst layer, which correlate to fcc-structured Ir and Cu, respectively. Additionally, the changes of the WAXS background signal in the q region of the anode, the catalyst layer before and during reaction reflect the change of solvent content in the MEA, which is related to the H2O content. As shown in Figure , the blue arrow indicates the shift in water content with reacting time at catalyst layer and also the varying water content at different layer of MEA. While the WAXS signal identifies the individual MEA layers, XRF simultaneously measures the characteristic fluorescence signal emitted at the X-ray beamfocused region, allowing solvated Cs to be detected. Figure shows a typical XRF spectrum at the anodic compartment with a high signal to noise ratio of the Cs Kα and Kβ peaks in the electrolyte (Table ). As a result, by measuring the WAXS and XRF simultaneously, the spatial distributions and dynamics evolution of H2O and solvated Cs content within the MEA can be observed. In this work, the Cs content is presented as intensity rather than concentration due to the uncertainty in H2O volume at different regions of the MEA.