A review on proton exchange membrane water electrolyzer: advances in heat and mass transport

Proton exchange membrane water electrolyzers (PEMWEs) are vital for green hydrogen production but face performance limitations due to coupled heat and mass transfer challenges. At high current densities, oxygen bubbles accumulate in the anode porous transport layer (PTL) and flow channels, blocking water access to catalytic sites and causing concentration polarization. Optimizing PTL pore structure and surface wettability reduces bubble adhesion and improves oxygen removal. Advanced flow field designs further enhance gas-liquid separation by balancing convection and pressure drop. Thermal management is equally critical. The low thermal conductivity of oxygen leads to hot spots at the PTL–catalyst interface, accelerating membrane degradation. Enhancing thermal conductivity, optimizing channel geometry, and applying active cooling strategies can mitigate thermal stress. Dynamic control of temperature and pressure is essential, as higher temperatures improve kinetics but promote bubble growth, while moderate pressure reduces bubble size at the cost of sealing complexity. Multiscale simulations and imaging provide insight into bubble dynamics, but challenges remain in fully resolving multi-physics coupling, optimizing material–structure synergy, and adapting to fluctuating renewable inputs. Future research should explore approaches such as coupling electrochemical and flow models across scales, multi-structure optimization, and interdisciplinary methods like fluid dynamics and machine learning, to effectively regulate heat and mass transfer and advance scalable, durable PEMWE systems.