Performance improvement of polymer electrolyte membrane-unitized reversible fuel cells using interdigitated flow fields under a fuel cell mode fully humidified condition

In polymer electrolyte membrane-unitized reversible fuel cells (PEM-URFCs), titanium felt is often used as the gas diffusion layer (GDL) for the oxygen electrode. While durable in electrolysis mode, it suffers from poor water management in fuel cell mode, leading to flooding and reduced performance. To address this issue, interdigitated flow fields are introduced to improve fuel cell mode performance by facilitating effective water removal and reactant transport. An experimental investigation evaluates the performance of PEM-URFCs with interdigitated flow fields in comparison to serpentine flow fields, with channel depths of 1.0 mm and 0.6 mm, resulting in four distinct configurations. The interdigitated flow field of 0.6 mm depth achieves a peak power density 42.7 % and 66.3 % higher than the serpentine flow fields of 0.6 mm and 1.0 mm depths, respectively, under a fully humidified condition. Under reduced air humidity (50 %), the serpentine flow field of 1.0 mm depth achieves slightly higher performance, but its advantage is marginal (9.2 %). In electrolysis mode, voltage variations among the different configurations are minimal, even under elevated hydrogen pressures. Overall, the study achieves a fuel cell peak power density of 0.404 W/cm² and a cell round-trip efficiency of 44.2 % at 0.4 A/cm², exceeding previously reported results in similar conditions. These findings highlight the potential of interdigitated flow fields to enhance the efficiency and performance of PEM-URFCs.