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.