Lung-inspired, fractal flow-fields hold great potential in improving the performance of polymer electrolyte membrane fuel cells (PEMFCs) by providing uniform gas distribution across electrodes and ensuring minimum entropy production whole system. However, inherent susceptibility to flooding renders their use inadequate at high humidity conditions. In-depth understanding water management lung-inspired is indispensable for implementation alternative outlet channel geometries or engineered...

In this paper, we present an experimental study on the development of gas diffusion layer (GDL) materials for fuel cells with dedicated water removal pathways generated using radiation induced grafting hydrophilic compounds onto hydrophobic polymer coating. The impact several material parameters was studied: carbon substrate type, coating load, grafted chemical compound and pattern design (width separation pathways). corresponding were characterized their capillary pressure characteristic...

Following our two previous publications on material synthesis and ex situ characterization, we present an experimental in study to evaluate the effects of using gas diffusion layers with patterned wettability at cathode side polymer electrolyte fuel cells. The operando performance was assessed traditional electrochemical diagnostics (such as polarization curves) combined pulsed analysis (PGA) method, which allows measuring mass transport losses. Neutron radiography performed simultaneously...

A novel type of fuel cell gas diffusion layer with patterned wettability is herein reported. The production hydrophilic patterns by radiation grafting depends on two main steps: electron beam activation and polymerization reaction. In this first part the series, we are giving extensive details about synthetic routes for modifying porous media's wettability. Two monomers (acrylic acid N-vinylformamide) were used hydrophilization fluoropolymer a parametric study was performed. Finally,...

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 radiation grafting technique synthesize GDLs with patterned wettability. Despite promise approach, current designs are empirically-driven which hampers development advanced patterns. design materials improved transport characteristics over range saturations, physically representative models can be...

We report on measured neutron cross section data for super-cooled water and ice by time-of-flight (TOF) transmission imaging. In particular, we demonstrate the use of high duty cycle (HDC)-TOF measurements to determine local aggregate state with spatial resolution, exploiting dependence mobility hydrogen atoms long wavelengths (>4 Å). While one can envision many different applications this method, example is provide insights into freezing mechanism during start-up polymer electrolyte...

Visualizing the water distribution in porous gas diffusion layers (GDLs) of operating polymer electrolyte fuel cells (PEFCs) is indispensable to understand impact management on performance. For this purpose, neutron and X-ray transmission imaging have been used for nearly two decades. Certain limitations inherent attenuation based methods can be overcome by applying dark-field imaging, which has ability selectively visualize structures micrometer size range. In study, we compare images GDLs...

Gas diffusion media is one of the main components affecting water management in polymer electrolyte fuel cells, which key for a high and stable performance. Building up on our previously designed gas layers (GDLs) with patterned wettability, we included this study customized microporous (MPLs) target to enhance effect hydrophilic pathways reduce mass transport losses. The MPLs were modified by introducing “weak points” using electron induced radiation grafting or local mechanical...

Despite being a promising technology for automotive applications, polymer electrolyte fuel cells still face challenges to reduce their complexity and cost. One challenge is achieve good humidification, which essential cell membrane, without expensive external humidifiers. Here we present an evaporative cooling concept that manages humidification simultaneously, does not require any additional layer the structure of cell. To this aim, water flows in itself through small number flowfields’...

High intensity ultrasound can be used for the production of novel nanomaterials, including metal oxides. According to previous works in this field, most notable effects are consequence acoustic cavitation. In context, we have studied preparation different materials presence ultrasound, N-doped TiO2 nanopowder, NiTiO3 nanorods and MnOx thin films. Ultrasound did not show a significant effect all cases. Exclusively reduction final particle size occurs upon ultrasonic irradiation. From these...

Coating load and distribution in gas diffusion layers (GDLs) for polymer electrolyte fuel cells (PEFCs) have a major influence on mass transport losses. To be able to optimize the coating get more accurate data about of PEFC performance, better characterization techniques are necessary. Common analysis limited selected sections material, or they not sensitive small amounts coating. We propose new methodology complete description GDL structure by combining high-resolution X-ray tomography...

Polymer electrolyte fuel cells (PEFCs) with interdigitated flow fields were operated modified gas diffusion layers (GDLs). Interdigitated have dead-ended channels, which forces the to convectively through GDLs outlet channels and significantly reduces mass transport losses. However, when using conventional GDLs, water accumulation at end of inlet results in an increased unpredictable pressure drop, translates unstable performance. This has prevented so far use this kind a stack...

We demonstrated the use of a neutron grating interferometer setup (nGI) with significantly improved contrast-to-noise ratio operando dark-field (DF) contrast visualization water in gas diffusion media (GDM). The nGI parameters were optimized such way that we could perform DF imaging fully operational fuel cell including two GDM layers (anode and cathode side). is sensitive to size shape microstructures principle not influenced by large clusters present flow field channels. Thus, can be...

The unassisted cold-start capability of polymer electrolyte fuel cells (PEFCs) remains challenging for large-scale automotive applications. Various studies have shown that the freezing produced water at cathode catalyst layer (CL) and gas diffusion (GDL) interface blocks oxidant leads to a failure. However, impact GDL properties, including substrate, size, hydrophobicity, on behavior supercooled is yet be thoroughly investigated. We use differential scanning calorimetry perform...

We present the operando performance of modified gas diffusion media (GDM) in polymer electrolyte fuel cells (PEFCs) complemented by neutron imaging and pulsed analysis, following our previous publication on synthesis water distribution GDMs. tested different types hydrophobic GDMs: a commercial GDM, GDM with highly porous microporous layer (MPL) other crack-free MPL contrasted them to GDM. The materials consists layers (GDL) patterns hydrophilic regions MPLs. To enhance GDL patterned...

The start-up of polymer electrolyte fuel cells (PEFCs) at sub-zero temperatures (cold-start) is a challenge for cell designers and operators. freezing water in the can cause shutdown severe damages to components. However, produced electrochemical reaction pure enough be present super-cooled state (liquid) (1). Methods that allow visualizing location events during cold-starts help understand which parameters influence phase transitions. For this purpose our group has been using energy...

The gas diffusion layers (GDLs) play several important roles in polymer electrolyte fuel cells (PEFCs): conduction of heat and electrons, mechanical integrity opposite-direction transport gases liquid water. This product water is transported by capillary forces [1] throughout the GDL, forming tortuous pathways. State-of-the-art GDLs do not provide optimal characteristics for simultaneous permeability oxygen diffusivity. To address this issue, we are developing new with patterned wettability...

In polymer electrolyte fuel cells (PEFCs), the porous gas diffusion layer (GDL) plays a multiple role in terms of transport. The solid phase consisting carbon fibers is responsible for electrical conduction and heat removal, void space provides pathways both supply gaseous reactants removal liquid water. This function results contradictory set requirements material characteristics: high thermal conductivity phase, permeability volume occupied by water diffusivity remaining transport are...

The water management in PEFCs is a rather complex issue. On one hand side, some needed order to hydrate proton conductive membrane and ionomer the catalyst layers. Therefore, humidified gases are fed into cell. other hand, excessive amounts of porous layers lead blockage available pores for gas transport consequently increased mass transfer limitations, especially at high current densities when large produced. diffusion (GDLs) highly carbon fiber materials which sandwiched between electrodes...

Further improvements in power density of polymer electrolyte fuel cells (PEFCs) are required to lower the cost. At high current densities, mass transport related resistances limit performance due to, mainly, a poor water management within cell. It is therefore paramount develop advanced strategies maximize output. In this context, diffusion layers play notable role. They must ensure efficient gas toward catalyst layer while removing electrochemically produced liquid opposite flow direction....

The distribution of water in operating polymer electrolyte fuel cells (PEFCs) has been and remains an important question, many researchers academy industry have studied the topic over last decade. Among methods used to measure this distribution, neutron imaging played a significant role owing its excellent transparency for cell materials, requiring minimal compromises on design, very good sensitivity liquid water. In classical “through plane imaging” experiments (neutron beam perpendicular...

The development of advanced water management strategies for polymer electrolyte fuel cells (PEFCs) could enable further improvements in power density, and therefore decrease the cost. A recently developed approach, consisting on electron radiation grafting using masks, has been utilized to fabricate gas diffusion layers with patterned wettability [1]. These novel materials feature hydrophilic, straightforward pathways transport liquid water; hydrophobic, low-resistance domains reactant gases...

The water management in polymer electrolyte fuel cells (PEFC's) needs to be properly balanced maximize the power output of cell. membrane requires hydrated order proton conductive. However, since transport and gas reactant occurs through same media, so called diffusion media (GDM), accumulation GDM can block access gases catalyst limiting performance is usually composed two layers: layer (GDL) microporous (MPL). In majority cases GDL consist a highly porous structure made carbon fibers...