Breathable Gas-Evolving Electrodes in Electrochemical Energy Devices

Gas-evolving electrochemical devices are fundamentally constrained by gas bubble formation at the electrode-electrolyte interface, which leads to active site blockage, increased overpotentials, and compromised operational stability. Breathable gas-evolving electrodes (BGEs) have recently emerged as a transformative strategy to eliminate bubble-related limitations by enabling in situ gas release through hydrophobic porous membranes. However, a comprehensive overview of recent advancements in BGEs, particularly with respect to their underlying mechanisms, remains lacking. This review first summarizes key architectural advancements in BGEs across water electrolysis, Zn-air batteries, direct liquid fuel cells, and gas purification and separation technologies. We then establish a unified mechanistic framework for gas release in BGEs, identifying two governing pathways: (i) in situ gas-phase release at the gas-liquid interface and (ii) liquid film rupture-induced bubble release. Finally, we critically discuss the remaining challenges that limit the practical deployment of BGEs. Perspectives are provided on future research directions toward mechanically robust and scalable BGE architectures capable of sustaining bubble-free operation at high current densities.