Nanostructured self-humidifying membrane electrode assemblies: toward efficient water management in air-cooled proton exchange membrane fuel cells

Effective water management is essential for improving the performance of air-cooled proton exchange membrane fuel cells (PEMFCs). While extensive efforts have been made over the past decades to design advanced flow field architectures and external humidification systems to alleviate membrane electrode assembly (MEA) dehydration, these strategies often increase the structural and operational complexity of PEMFC systems. A promising alternative lies in engineering the intrinsic material properties of MEAs to enable self-humidification. In this review, we first elucidate the fundamental mechanisms governing water transport within the MEA and assess the detrimental effects of inadequate water regulation on fuel cell performance. We then provide a comprehensive overview of diagnostic techniques for water management, encompassing both physicochemical and electrochemical approaches. Emphasizing self-humidifying capabilities, we highlight a range of innovative strategies aimed at mitigating MEA dehydration. Furthermore, we conduct a comprehensive discussion on the synergistic modification of multiple components and the influence of improvement strategies on stability. Finally, we outline prospective research directions for the development of self-humidifying MEAs.