Proton‐Exchange Membrane Fuel Cells for Aviation: The Unresolved Challenges Behind Zero‐Emission Flight

ABSTRACT Hydrogen‐powered aviation increasingly positions proton‐exchange membrane fuel cells (PEMFCs) as a promising pathway toward zero‐emission flight. However, the deployment of PEMFCs in aircraft remains constrained by altitude‐dependent electrochemical behavior, strict humidity and thermal requirements, catalyst degradation under sustained high current densities, and the complexity of maintaining stable water and reactant management in low‐pressure flight environments. These challenges distinguish aviation PEMFCs fundamentally from their automotive and stationary counterparts. This perspective consolidates the key scientific and engineering limitations that currently restrict the scalability and long‐term reliability of PEMFC systems for aviation applications. Particular emphasis is placed on membrane hydration stability, impurity‐tolerant catalyst architectures, lightweight and high‐specific‐power stack design, and the system‐level implications of balance‐of‐plant (BoP) integration under dynamic flight conditions. The roles of low‐ and high‐temperature PEMFC architectures, as well as hybrid fuel‐cell–battery configurations, are examined in the context of mitigating these constraints. By synthesizing material‐level degradation mechanisms with electrochemical and system‐level interactions across different flight phases, this article highlights that sustained performance in aviation of PEMFCs depends on a coordinated control of hydration, thermal balance, and electrochemical kinetics rather than on isolated component optimization. Building on this analysis, a focused research roadmap is outlined that identifies the advances required in membrane chemistry, catalyst durability, thermal management, and stack engineering to enable reliable, megawatt‐class PEMFC power units suitable for zero‐emission aviation.