Voltage decreases once again upon switching back to fully humified air. Synchronous measurements of EIS and neutron imaging were conducted and repeated throughout this process. The impact of dry-wet gas switching on the overall water content within the fuel cell is clearly visible in Fig. . Overall water content steadily increases with humidified gas supply and decreases with the introduction of dry gas. The fluctuation trend of cell voltage exhibits a reverse pattern compared to the evolution of overall water content. The changing water content can be easily realised by dry-wet gas switching, which is also faster than the RH control. thickness was calculated can be seen in the neutron imaging collection and data analysis part of the experimental procedures section. The water mapping is rotated in 3D, and the height and colour scale are proportional to the water thickness (mm).