Impact of drying on membrane electrode assembly morphology and performance in PEM electrolysis: insights from X-ray tomography and radiography

Abstract

Proton exchange membrane electrolysis cells (PEMECs) are a crucial technology for generating “green hydrogen”, a sustainable energy carrier and versatile platform for synthesizing several chemicals. In the life cycle of a PEMEC, various process stages bare risks of accelerated aging, impacting long-term performance. In the stages of transport and storage of water-filled cell assemblies, a common practice in industry, cation contamination or frost can lead to the degradation of the membrane electrode assembly (MEA) even before its operation. Therefore, as an alternative to transporting and storing the MEA in a hydrated state, this work investigates the possibility of drying the MEA within the cell assembly under controlled conditions to prevent such degradation phenomena. Potential drying induced MEA functionality changes were analyzed using in operando methods, focusing on electrical and gas barrier properties. Butler-Volmer kinetics and electrochemical impedance spectroscopy allowed the allocation of potential performance losses to components. Furthermore, in situ and ex situ X-ray computed tomography (XCT) and optical microscopy investigations gave insights into drying-induced morphological changes within the MEA. In total, three distinct morphological changes were observed and consistently identified: membrane swelling, catalyst layer cracking, and reinforcement detachment, with each posing potential limiting factors for the scalability of the controlled drying process. Ultimately, no significant impact on electrical and gas barrier properties was observed, indicating that the drying process and morphological changes did not adversely affect the short-term operation of the PEMEC.