Figure compares the XRF Cs signal of two anolyte concentrations, showing a notably larger intensity at the cathodic compartment with the 0.1 M CsHCO3 electrolyte compared to the 0.01 M CsHCO3 electrolyte. In both experiments, there is no observable salt precipitation (Figure & 3), all Cs signals are considered to come from the solvated Cs (i.e., Cs + ) at concentrations below 8 M which is the solubility limit for Cs2CO3. Figure indicates that there is a strong correlation between the concentration of Cs + in the bulk electrolyte and the Cs + transport towards the cathode. Furthermore, both experiments show a correlation between the Cs + signal, cell voltage and operating time. In general, as the cell voltage increases and operating time passes, the solvated Cs + tends to accumulate within the GDL and, to a lesser extent, at the Cu catalyst layer. In Figure , showing the H2O signal, there is a noticeable intensity peak in the membrane region. This heightened signal can be attributed to the membrane's structural composition and significant water-holding capacity, which results in a high scattering effect in the AEM. As the membrane's internal structure is not anticipated to undergo substantial alterations, the observed variations in signal intensity in this region can be attributed to changes in H2O content. As these figures only provide an overview, detailed analysis and discussions on transport mechanisms and the correlation between Cs + and H2O are presented in the next section.