Highly Stable Gas Diffusion Layer with Anti-Flooding Characteristics Under High-Current Operation for the Polymer Electrolyte Fuel Cell Applications
Authors: Park Young Je , Choi Won young , Choi Hyunguk , Choi Seo won , Cho Hyeon E , Lee Kang Taek , Jung Chi-Young 
Published: December 2024

In the global energy market, several major unions and industries release the roadmap that utilize the hydrogen as the energy carrier, to achieve the fully electrification of transportation for carbon neutrality. Polymer electrolyte fuel cells (PEFCs) are suitable for heavy-duty vehicles (HDVs) due to advantages such as fast refueling (< 5 min), long driving range (> 300 miles), and higher efficiencies (>60%) [1]. HDVs often encounter tougher conditions than light-duty vehicles (LDVs), including longer distances, extended operating hours, and challenging terrain. The ORR electrode running under such environments suffers from severe liquid water flooding of pores. Addressing this issue requires controlling the water management, crucial for mitigating voltage losses at high current density (HCD)[2]. The cathode GDL acts as a central hub of the bidirectional flow during the operation, achieving an optimal balance between electrode and channel. The overlapping of liquid and gas pathways can lead to a significant increase in mass transport resistance (MTR). Engineering the liquid/gas highways to avoid the overlapping, many researchers have spent much effort on breakthrough strategy for the flooding problem following parameters: pore size distribution, surface roughness, and surface wettability[3-4]. Within the cell, water molecules generated by the ORR condense in various places. Adjusting the microstructure serves as an effective method for managing the pathway of condensed liquid water [5]. Especially, condensed water at the CL-MPL interface along the in-plane is challenging to discharge through microporous due to capillary pressure. To dramatically improve the performance, it is essential to clearly understand the correlation between three-dimensional microstructure of the MPL, CL-GDL interface, and the mass transport resistance at HCD.
In this study, we proposed a straightforward strategy that significantly reduces MTR by simple structural change from non-penetrative crack to penetrative crack via carving the designed MPL crack. Firstly, advanced transparent XRM device enables X-CT analysis under conditions that mirror the actual PEFC operating environment. The voids at the CL-MPL interface are considered to serve as potential drop sources related with MTR, where the vapor generated by the ORR is likely to condense. Secondly, to discharge the condensed liquid at the interfaces under low-temperature and/or high-current density conditions, we have explored microstructural benefits of penetrative cracks. All parameters known to be associated with liquid water transport are fully-controlled except for crack microstructure (crack-free, non-penetrative crack, and penetrative crack). Finally, the stability test at HCD indicated a notable enhancement of liquid discharge and gas injection in GDLs with the penetrated cracks. Our results suggest that penetrative crack with concise fabrication method can provide stable water management capability for improving the performance at HCD of PEFC.
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[5] Wen, Qinglin, et al. "Janus gas diffusion layer for enhanced water management in proton exchange membrane fuel cells (PEMFCs)." ACS Energy Letters 7.11 (2022): 3900-3909.