Leveraging the XRF experiments to observe the variations in Cs + content at the catalyst layer, the role of local Cs + concentration effects on selectivity of CO2 reduction is investigated. Figure shows the electrochemical characterization during the in-operando experiments using 0.01 M and 0.1 M CsHCO3 (shown in Figure ). Liquid products achieved from parallel experiments without applying X-ray for each current density are provided in Table using a fresh MEA.