The Role of Operating Temperature on Pore‐Scale Gas Transport in Polymer Electrolyte Membrane Electrolyzers

This study clarifies the critical relationship between operating temperature and two‐phase flow behavior in polymer electrolyte membrane (PEM) electrolyzers by investigating pore‐scale gas bubble transport in the anode porous transport layer. Higher temperatures (80 °C vs 40 °C) result in a lower total bubble volume fraction and smaller bubble diameters, driven by enhanced water transport and increased bubble detachment rates. Abstract In this study, the effects of operating temperature on pore‐scale gas bubble transport in a carbon‐based anode porous transport layer (PTL) of a polymer electrolyte membrane (PEM) electrolyzer is revealed using operando X‐ray computed tomography (CT). Higher temperature operation (80 °C compared to 40 °C) led to a lower total gas bubble volume fraction in the PTL (0.25 to 0.17; 32% lower), which is attributed to improved water transport and gas removal. Higher temperatures led to fewer bubbles in the PTL (13% less at 80 °C compared to 40 °C) as well as a greater occurrence of smaller bubbles (35% increase in skewness of the bubble size distribution), and this behavior is attributed to faster rates of nucleation and bubble detachment from the electrode. The formation of gas slugs is also observed in the anode channels at 60 °C and 80 °C, which is attributed to the faster detachment and coalescence of bubbles from the PTL/flow field interface. This study clarifies the critical relationship between operating temperature and two-phase flow behavior in polymer electrolyte membrane (PEM) electrolyzers by investigating pore-scale gas bubble transport in the anode porous transport layer. Higher temperatures (80 °C vs 40 °C) result in a lower total bubble volume fraction and smaller bubble diameters, driven by enhanced water transport and increased bubble detachment rates. Abstract In this study, the effects of operating temperature on pore-scale gas bubble transport in a carbon-based anode porous transport layer (PTL) of a polymer electrolyte membrane (PEM) electrolyzer is revealed using operando X-ray computed tomography (CT). Higher temperature operation (80 °C compared to 40 °C) led to a lower total gas bubble volume fraction in the PTL (0.25 to 0.17; 32% lower), which is attributed to improved water transport and gas removal. Higher temperatures led to fewer bubbles in the PTL (13% less at 80 °C compared to 40 °C) as well as a greater occurrence of smaller bubbles (35% increase in skewness of the bubble size distribution), and this behavior is attributed to faster rates of nucleation and bubble detachment from the electrode. The formation of gas slugs is also observed in the anode channels at 60 °C and 80 °C, which is attributed to the faster detachment and coalescence of bubbles from the PTL/flow field interface. Advanced Science, Volume 12, Issue 44, November 27, 2025.