Enhanced water management by construction of ZrO2-Based hydrophilic channels in microporous layers for high-performance proton exchange membrane fuel cell

Abstract

Effective water management is crucial for achieving high performance proton exchange membrane fuel cell (PEMFC) under various operating conditions. However, addressing the challenges of maintaining proton conductivity and preventing electrode flooding under fluctuating humidification remains difficult. In this study, a method is employed to address the issue by creating hydrophilic sites within the hydrophobic network of the microporous layer (MPL). On one hand, as preferred channel to guide liquid water through MPL, the incorporated hydrophilic ZrO₂ powder facilitates water expelling under wet conditions, while keeping other pores coated with hydrophobic polytetrafluoroethylene (PTFE) as gas diffussion routes. On the other hand, the ZrO₂ could adsorb water to hydrate the membrane, and thus demonstrating a self-humidifying effect under low-humidity conditions and enhances the performance of the PEMFC. The distribution and content of hydrophilic sites in the MPL are explored to investigate their impact on cell performance under varying humidity conditions. The results showed that when hydrophilic sites occupy 50 wt% of the total hydrophobic carbon powder and are uniformly distributed in the MPL, the performance is optimal. Under low and high relative humidity conditions, the peak power density of the cell increased by 22 % and 20 % compared without ZrO₂, respectively. These findings indicate that the MPL with a self-humidifying effect under low humidity and water/gas separation capability under high humidity can enhance mass transfer and energy efficiency, offering a promising strategy for optimizing PEMFC water management.