Heratec – Scale-up of Gas Diffusion Layers with Patterned Wettability for Improved Fluid Transport in Hydrogen Fuel Cells

Abstract

Competitive transport pathways within porous electrodes fundamentally limit the performance of fuel cell devices. While humidification of the system is necessary to provide proton conductivity to the polymeric membrane and ionomer in the catalyst layer, excessive water accumulation in the gas diffusion layer impedes gas transport, resulting in mass transfer performance limitations. In this context, the microstructure and surface chemistry are critical and impact the transport of fluids, mass, charge, and heat, as well as wettability and electrochemical activity. The possibility of creating localized hydrophilic channels for water transport in the gas diffusion layer offers a pathway for advanced strategies to optimize multiphase transport in hydrogen fuel cells. In the past, several techniques have been attempted to create dedicated pathways for water to be transported through the gas diffusion layer, such as layer perforation, local coating deposition, and plasma irradiation [1]–[3]. However, the industrial application of these techniques is limited, due to problems with the mechanical stability, pattern quality, and durability of the applied coating.To approach the problem of water management in polymer electrolyte fuel cells, we have invented a synthetic method based on electron radiation grafting [4]. In previous work, we demonstrated that this tunable method can be readily employed to create gas diffusion layers with patterned wettability [5], [6]. Laboratory experiments demonstrated that the use of patterned gas diffusion layers improved overall fuel cell performance (i.e., power density at high current density) by 10 to 30%, depending on the operating conditions [7]. Moreover, follow-up studies demonstrated that the integration of the modified gas diffusion layer can be used to enable completely new cell design using an interdigitated flow field. Interdigitated flow fields have been demonstrated to substantially improve the cell performance in comparison to conventional cells with parallel flow fields, but current industrial implementation is limited due to stability issues caused by water accumulation in the flow field [8]. The modification of gas diffusion layers with localized wettability demonstrated stable operation of a laboratory-scale cell with very low pressure drop [9]. Finally, the application of patterned GDLs has been proven to enable evaporative cooling, which offers the potential of removing external gas humidification of the cells and cooling fluids [10].Here, we discuss the scale-up potential, industrial application and commercial aspects of our synthetic method to produce gas diffusion layers with localized wettability. In addition, we elucidate the process tunability and discuss the in-situ performance of the manufactured materials. Finally, we present an outlook of our future work focusing on the application of gas diffusion layers with patterned wettability in fuel cells of industry-relevant dimensions and at industry-relevant operating conditions.