Synergistic enhancement of porosity and conductivity in microporous layer via fluorinated CNT for PEMFC applications

Abstract

This study presents the development of a superhydrophobic fluorinated carbon nanotube (F-CNT) material via chemical grafting of 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (PFDTES) onto carbonylated carbon nanotube (CNT). The F-CNT were composited with XC-72 carbon black (CB) to fabricate a novel microporous layer (MPL) for proton exchange membrane fuel cell (PEMFC). The effects of PFDTES modification on the surface chemistry, crystal structure, hydrophobicity, and morphology of F-CNT were systematically characterized. F-CNT@CB-based MPL exhibited increased porosity (72.6%), a high fraction of macropores (25–45 μm), and a significant improvement in surface hydrophobicity, with the water contact angle increasing from 139° to 160°, while the in-plane electrical resistivity was reduced to 7.1 mΩ·cm. Under 80% and 100% relative humidity, the PEMFC assembled with F-CNT@CB demonstrated the highest limiting current densities (1.35 and 1.29 A/cm²) and peak power densities (473 and 427 mW/cm²), alongside the lowest mass transport impedance among all tested samples. These results confirm that the incorporation of F-CNT effectively enhances water and gas management within MPL, significantly improving PEMFC performance under humid operating conditions. This work offers a promising approach for designing high-performance, humidity-tolerant fuel cell electrode structures.