Effective water management through microporous-layer wettability control for high power density in low-temperature fuel cells

Water management in microporous layers (MPLs) is a major challenge in low-temperature fuel cells. This study introduces a simple method to fabricate a biphilic MPL with in-plane hydrophilic and hydrophobic regions. The hydrophilic ratio is systematically controlled to analyze its effect on cell performance. Surface wettability is selectively modified via plasma treatment and subsequent NaOH treatment, while preserving the original structure. Contact-angle measurements and energy-dispersive X-ray spectroscopy confirm successful modification. Among the tested configurations, a hydrophilic ratio of 25.0 % exhibits the most favorable performance among the tested conditions: a 28.8 % increase in current density at 0.6 V and 22.2 % increase in maximum power density relative to the hydrophobic MPL. Electrochemical impedance spectroscopy reveals improved mass transfer in the biphilic structure. A 5-h water-drainage test confirms its superior water-removal capability. Comparative analysis with previous studies employing similar surface modification techniques further demonstrates enhanced performance of the proposed MPL, which exhibits the largest improvement in current density at 0.6 V among reported results. These findings indicate that in-plane wettability patterning promotes liquid–gas pathway separation. The proposed method is simple, scalable, and applicable for improving liquid–gas management and performance in low-temperature fuel cells.