Impact of gas diffusion layer with a gradient pore size distribution on liquid water transport in proton exchange membrane fuel cell

Optimizing the microporous layer (MPL), a key component of gas diffusion layer (GDL) in proton exchange membrane fuel cells (PEMFCs), is a promising strategy for enhancing water removal and ensuring long-term stable operation at high current densities. This study proposes a dual-MPL (VXC72-G-MPL), fabricated by sequentially depositing graphene layer and Vulcan XC72 (VXC72) layers onto a macroporous substrate (MPS). Measurements reveal that the graphene layer provides superior thermal conductivity while effectively mitigating MPL penetration into the MPS. Furthermore, the architecture establishes a hierarchical pore-size gradient, transitioning from mesopores to micropores from the MPS toward the catalyst layer (CL). These synergistic features accelerate liquid water transport efficiency within the GDL. In PEMFC tests, the VXC72-G-MPL membrane electrode assembly (MEA) demonstrates robust performance under 100%, 125%, and 150% relative humidity (RH), yielding voltages of 0.41 V, 0.42 V, and 0.36 V at 2 A cm −2 , respectively, significantly outperforming the conventional VXC72-MPL. Furthermore, after a 24 h accelerated steady-state test (0.4 V, 60 °C, and 150% RH), the VXC72-G-MPL MEA shows only 1.7% performance loss, a substantial improvement over the 15.3% decay for the VXC72-MPL MEA. The superior performance and stability confirm the excellent water removal capacity of the proposed dual-layer MPL architecture.