Hydrogen production's crucial role in the transition to cleaner energy is underscored by the challenges explored in a recent study on polymer electrolyte membrane water electrolyzers (PEMWEs). Researchers delved into the impact of mass transport limitations, particularly when utilizing water vapor as the reactant. The study identified how oxygen gas bubbles during the oxygen evolution reaction can impede the flow of liquid water essential for efficient hydrogen production. By focusing on factors like limiting current density, relative humidity, and backpressure, the research showcased the inhibiting effects of water vapor on high current densities due to reduced catalyst activity and membrane dry-out. Notable findings emphasized the importance of membrane hydration and highlighted the differences in performance between vapor-fed and liquid-fed systems. The study's insights offer a pathway to optimizing electrolysis for hydrogen production, supporting global efforts towards renewable energy systems and encouraging advancements in cleaner hydrogen production technologies. By addressing operational challenges and refining strategies, the research paves the way for sustainable energy solutions and underscores the potential of vapor-fed systems in diversifying hydrogen production under various conditions.