Effects of Ionomer Content on Transient Response Characteristics of PEMFCs Under Dynamic Loading Conditions

The transient response characteristics of a proton exchange membrane fuel cell (PEMFC) can significantly impact its performance and lifespan, particularly in transportation applications where rapid and frequent changes in power demand occur. Various factors contribute to the transient response of fuel cells, including the dynamics of proton and gas transport. While the ionomer content has a discernible effect on these transport processes at a steady state, its specific influence on the dynamic response of fuel cells remains an underexplored area of research. In this paper, a transient, two-dimensional, two-phase, and non-isothermal model combined with catalyst agglomerate was constructed. The transient response characteristics of voltage and local current density (LCD) uniformity are investigated for three different ionomer volume fractions within the common range. The results indicate that an increase in ionomer content reduces the ohmic loss in the dynamic loading process, leading to a reduction in voltage undershoot and an improvement in voltage dynamic characteristics. As for LCD uniformity, due to the limited proton transport capacity, the LCD near the proton exchange membrane in the catalyst layer is much higher than that near the micro-porous layer at the moment of the current density loading, resulting in a temporary overshoot of the LCD uniformity. Increasing the ionomer content can enhance the proton transport capacity, thus reducing the overshoot of the LCD uniformity. These findings will help guide the design of catalyst layers in fuel cells and advance their application under dynamic operating conditions.