Transient Gas Saturation in Porous Transport Layers of Polymer Electrolyte Membrane Electrolyzers

Here, we elucidated the dynamic gas transport behavior in the anode porous transport layer (PTL) of polymer electrolyte membrane (PEM) electrolyzers via in operando synchrotron X-ray imaging. The imaging results showed that the gas saturation in the PTL reached steady state more rapidly with a steep current density ramp up and a shallow ramp down (compared to a shallow ramp-up and a steep ramp-down). Additionally, the gas accumulation had faster response time than gas removal due to the relatively slow migration of residual gas out of the PTL. Furthermore, we investigated the impact of gas response behavior on gas saturation during intermittent electrolyzer operation. Intermittent operation led to an increase in residual gas accumulation, which negatively impacted the electrolyzer performance. Our results are key for informing design and operating strategies for mitigating such hysteresis effects and improving the performance of PEM electrolyzers when coupled with intermittent renewable energy sources.