When a potential is applied (Figure ) and current is generated, the AEM becomes slightly less hydrated (ΔH2O < 0) due to H2O consumption and the oxygen gas formation at the anode. This aligns with the study by Disch et al., that measured the changes in H2O content using neutron imaging. A deflection point is observed at a depth of 0.18 mm, where the H2O content in the GDL starts to increase. This change indicates that electroosmotic drag from Cs + ions predominates in the transportation of H2O across the AEM towards the catalyst, particularly in regions where the electric field is pronounced. Subsequent to the electroosmotic drag across the AEM, as the H2O content increases in micro-porous layer, it will diffuse further into the macro-porous layer. This process is assumed to be diffusion rather than electroosmosis due to the negligibly small electric field within this region.