Elucidating the rib-channel effect on the two-phase flow evolution and performance of proton exchange membrane electrolysis cell

Two-phase flow transport at proton exchange membrane electrolysis cell (PEMEC) anode is influenced by flow field design. This study combined optical visualization, machine learning-driven bubble detection and electrochemical diagnose to quantify bubble coverage evolution and PEMEC two-phase flow patterns. Model is based on YOLOV8, with F1-score approximately 0.95, capturing most bubbles. Bubble coverage increases with current density, at 2.5 A cm⁻², bubbles converge into annular flows, covering 49.70 % flow field and causing rapid mass transfer loss. Increasing water supply flow rate from 10 to 100 mL min⁻¹ reduces 33.66 % bubble coverage and approximately 16 mV mass transfer overpotential, whereas adjusting temperature has little effect. Bubbles form more at rib edges than channel middles, hindering discharge in rib regions. Adjusting rib-channel ratio and flow channel width reduces bubble blockage from their functional differences. Larger ribs reduce ohmic loss but excessive size increases mass transfer loss. Under 3 A cm⁻², 2.0 mm:2.0 mm flow field performs best. With fixed 1.0 rib-channel ratio, electrolysis voltage for 1.0 mm width is approximately 85 mV lower than 3.0 mm width, while 1.5 mm width presents optimal choice. This study provides a quantitative two-phase flow evolution method and design criteria for high-performance PEMEC, aiming green hydrogen production.