Key points are not available for this paper at this time.
Porous transport layers (PTL) in polymer electrolyte membrane electrolysis cells ensure gas/liquid mass transport at the anode, and determine the feasibility of high current density operation up to the limiting current density (LCD). This study examined the effect of anode PTL properties on LCD by varying porosities of 45 %, 56 %, and 72 %. Electrochemical characterizations suggest that the mass transport limitation leads to an abrupt increase in the electrolysis voltage and membrane dehydration, and also indicate that the PTL with the largest porosity of 72 % achieves the largest LCD compared to the other two PTLs with smaller porosities. Moreover, visualization experiments with a high-speed microscope captured the bubble detachment sites at the interface between flow channel and PTL, and reveal that a larger PTL porosity increases the density of the detachment sites. Additionally, a correlation emerges between the bubble flow regimes at the anode channel and periodic changes of the current density. A numerical analysis incorporating the visualized bubble behavior into the boundary condition successfully predicts the dependence of the porosity on the LCD, in agreement with the experimental results. The analysis also demonstrates that a larger porosity contributes to reducing the gas saturation and enhancing the LCD. • Electrolysis voltage and mass transport overvoltage increase sharply at the LCD. • Current density, ohmic resistance, and bubble behavior synchronize at the LCD. • Bubble detachment sites are captured and integrated into the LCD simulation. • Higher PTL porosity reduces the mass transport resistance and enhances the LCD.
Ma et al. (Thu,) studied this question.