Gradient Hydrophobic Microporous Layer for High-Performance Proton-Exchange Membrane Fuel Cells

The hydrophobicity of microporous layers (MPLs) plays an important role in water management and performance enhancement of proton-exchange membrane fuel cells (PEMFCs). In this study, we demonstrate a facile synthetic strategy for preparing a gradient hydrophobic MPL. The superhydrophobicity of the MPL is achieved by chemically grafting carbon black with dodecyltrimethoxysilane (DTMS). The MPL with gradient hydrophobicity is constructed with hydrophobic DTMS-functionalized carbon black integrated with a fine proportion of hydrophilic carbon black, demonstrating advanced water drainage capability. As employed in a PEMFC, the as-fabricated gradient hydrophobic MPL shows a significantly improved performance compared to a single hydrophobic MPL. The PEMFC loaded with the optimum gradient hydrophobic MPL delivers maximum power densities of 860.7 and 733.5 mW cm^–2 at relative humidities (RHs) of 30 and 60%, respectively. The results presented herein provide a new strategy for the construction of gradient hydrophobic MPLs for adaptable PEMFCs.