Sectionalized Mechanism of Gas–Liquid Transport and Structural Optimization of Grooved Gas Diffusion Layers within PEMFCs

Grooved gas diffusion layers (GDLs) have garnered significant attention due to their superior gas–liquid transport potential. However, existing studies lack systematic exploration of the mass transfer mechanism and liquid water distribution uniformity. In this work, a three-dimensional two-phase full-scale cell model is constructed to systematically investigate the electrochemical performance and gas–liquid transport characteristics of perpendicularly grooved GDLs. The results demonstrate that perpendicularly grooved GDLs outperform groove-free GDLs, with the optimal groove width of 200 μm achieving a current density of 1.664 A/cm2 at 0.4 V, representing a 4.9% improvement. The core mechanism lies in the capillary pressure gradient (∇PC) and Sherwood number (Sh) in the GDL region beneath the gas flow channel (GFC), which are significantly increased. ∇PC and Sh are enhanced by 46.89% and 3.40%, respectively. However, it is notably found that the gas–liquid transport efficiency in the GDL region beneath the rib fails to be enhanced synchronously. The sectionalized transport mechanism leads to a 142.7% increase in liquid water distribution unevenness compared to groove-free GDLs. Therefore, a novel diagonally grooved GDL structure with high reaction uniformity is proposed. By connecting different regions of GDL, the diagonal grooves break the limitation of traditional sectionalized transport, reducing the unevenness of liquid water distribution by 70.6% compared to perpendicularly grooved GDLs. The study also finds the diagonal grooves further reduce the unevenness of liquid water distribution through improving mass transfer between adjacent channels in three-channel cell fuels. This study provides theoretical guidance for the analysis of gas–liquid mass transfer mechanisms and structural optimization of grooved GDLs. It is of great significance for achieving the synergistic optimization of GDL performance and durability.