Abstract
Engineering the wettability and microstructure of gas diffusion layers offers a powerful strategy to optimize water management in polymer electrolyte fuel cells. To this goal, we recently developed a radiation grafting technique to synthesize GDLs with patterned wettability. Despite the promise of this approach, current designs are empirically-driven which hampers the development of advanced wettability patterns. To design materials with improved transport characteristics over a range of water saturations, physically representative models can be employed for the bottom-up design of gas diffusion layers with local variations in hydrophilicity. In this paper, pore network models using topology and size information extracted from high resolution tomographic images of three common gas diffusion layer materials are presented with patterned wettability. We study the influence of the substrate microstructure, the hydrophobic coating load, and the hydrophilic pattern width. It is shown that tuning the wettability leads to enhanced phase separation and increased diffusive transport which is attributed to decreased gas phase tortuosity. The network model elaborates on previous experimental studies, shedding light on the effectiveness of the radiation pattern transference and the importance of matching the masking pattern with the substrate microstructure. The work opens the door for exploration of advanced patterns, coupled with flow from gas flow field designs.
Highlights
Pore Network Modelling of Capillary Transport and Relative Diffusivity in Gas Diffusion Layers with Patterned Wettability
The gas diffusion layers (GDLs) is first coated with a hydrophobic polymer and irradiated with electrons using masks with slits, thereby activating the polymer coating in specified locations and patterns dictated by the mask
The SGL material has larger pores compared to Toray and Freudenberg and a wider Pore size distributions (PSD) and these larger pores are randomly distributed in the in-plane direction (Figure 1j)
Summary
Pore Network Modelling of Capillary Transport and Relative Diffusivity in Gas Diffusion Layers with Patterned Wettability. Avoiding flooding during PEFC operation is partially achieved through control of relevant operating conditions (e.g. temperature, pressure, relative humidity) that minimize water condensation within porous transport layers.[11,12,13,14,15] In addition, highly engineered porous materials are leveraged to optimize multiphase transport. In this context, the gas diffusion layers (GDLs) are central components that need to fulfill a number of important requirements, namely transport of reactants to catalytic layers and removal of electrochemically produced water, conduction of electrons and heat, and provision of mechanical support to the membrane-electrode assembly. The present study aims to explain the observed experimental results and provide a framework for aiding future optimization of the procedure
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