In summary, initially, no net Cs + movement is observed at OCV. When applying an electric field, the cations tend to migrate across the AEM towards the cathode. A concentration gradient causes the cations to diffuse from the micro-porous layer to the macro-porous layer. Due to the large free volume within the macro-porous layer, Cs + ions are accumulated at this region. Electroosmosis is verified as the dominating H2O transport mechanism during electrolysis across the AEM, while diffusion causes H2O to transfer further into the macro-porous layer due to the negligibly small electric field in this region.