Tailored Electrospun Gas Diffusion Layers for Polymer Electrolyte Membrane Fuel Cells PDF Download
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Author: Manojkumar Balakrishnan
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The polymer electrolyte membrane (PEM) fuel cell is a versatile alternative for the decarbonization of the transportation sector. However, high cost and limited durability of materials hinder widespread adoption. This thesis comprises two studies that aim to address both cost and durability of PEM fuel cells via the design of tailored gas diffusion layers (GDLs). First, electrospinning is presented as a platform to fabricate and design tailored GDLs with pore size gradients for the improved high current performance of PEM fuel cells. Specifically, the novel graded GDL was found to reduce ohmic resistance and improve mass transport performance. Next, the durability of electrospun GDLs was investigated via an ex situ accelerated degradation procedure. The degraded GDLs exhibited reduced hydrophobicity due to loss of surface groups and reduced electrical conductivity due to carbon degradation. This thesis offers insight into designing next generation, durable GDLs with tailored structures for PEM fuel cells.
Author: Manojkumar Balakrishnan
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The polymer electrolyte membrane (PEM) fuel cell is a versatile alternative for the decarbonization of the transportation sector. However, high cost and limited durability of materials hinder widespread adoption. This thesis comprises two studies that aim to address both cost and durability of PEM fuel cells via the design of tailored gas diffusion layers (GDLs). First, electrospinning is presented as a platform to fabricate and design tailored GDLs with pore size gradients for the improved high current performance of PEM fuel cells. Specifically, the novel graded GDL was found to reduce ohmic resistance and improve mass transport performance. Next, the durability of electrospun GDLs was investigated via an ex situ accelerated degradation procedure. The degraded GDLs exhibited reduced hydrophobicity due to loss of surface groups and reduced electrical conductivity due to carbon degradation. This thesis offers insight into designing next generation, durable GDLs with tailored structures for PEM fuel cells.
Author: Justo Lobato
Publisher:
ISBN:
Category : Science
Languages : en
Pages :
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Book Description
The Gas Diffusion Layer in High Temperature Polymer Electrolyte Membrane Fuel Cells.
Author: Pranay Shrestha
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Custom microporous layers (MPLs) were fabricated and designed to enhance fuel cell performance and water management at two specific operating conditions, operation without anode humidification and operation at high current densities. The two studies were aimed at addressing two challenges of water management, i.e., membrane dehydration and cathode liquid water flooding. The fuel cell performance and impedance measurements were paired with synchrotron X-ray visualization to quantify cell potential, membrane and mass transport resistances, and liquid water within gas diffusion layers (GDLs). The application of hydrophilic MPLs decreased the membrane resistance, and increased liquid water retention at the catalyst layer-MPL interface. MPLs with spatially graded PTFE content reduced the cathode GDL liquid water accumulation and oxygen transport resistance. Both MPLs led to increased fuel cell performance. The knowledge gained from this thesis can inform the design of next-generation fuel cell materials that further improve cell performance at desired operating conditions.
Author: Christian Siegel
Publisher: Logos Verlag Berlin GmbH
ISBN: 3832539174
Category : Science
Languages : en
Pages : 182
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Book Description
A three-dimensional computational fluid dynamics model of a high temperature polymer electrolyte membrane fuel cell, employing a high temperature stable polybenzimidazole membrane electrode assembly doped with phosphoric acid, was developed and implemented using a commercially available finite element software. Three types of flow-fields were modeled and simulated. Selected simulation results at reference operating conditions were compared to the performance curves and to segmented solid-phase temperature and current density measurements. For the segmented measurements, an inhouse developed prototype cell was designed and manufactured. The segmented cell was successfully operated and the solid-phase temperature and the current density distribution were recorded, evaluated, and discussed. Sequentially scanned segmented electrochemical impedance spectroscopy measurements were performed to qualitatively support the observed trends. These measurements were used to identify and determine the causes of the inhomogeneous current density distributions. An equivalent circuit model was developed, the obtained spectra were analyzed, and the model parameters discussed. This work helps to provide a better understanding of the internal behaviour of a running high temperature polymer electrolyte membrane fuel cell and presents valuable data for modeling and simulation. For large fuel cells and complete fuel cell stacks in particular, well designed anode and cathode inlet and outlet sections are expected to aid in achieving flatter quantities distributions and in preventing hot spots over the membrane electrode assembly area, and to develop proper start-up, shut-down, and tempering concepts.
Author: Jasna Jankovic
Publisher: Walter de Gruyter GmbH & Co KG
ISBN: 3110622726
Category : Technology & Engineering
Languages : en
Pages : 508
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Book Description
This book is a comprehensive introduction to the rapidly developing field of modeling and characterization of PEM fuel cells. It focuses on i) fuel cell performance modeling and performance characterization applicable from single cells to stacks, ii) fundamental and advanced techniques for structural and compositional characterization of fuel cell components and iii) electrocatalyst design. Written by experts in this field, this book is an invaluable tool for graduate students and professionals.
Author: J. Zachary Fishman
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: Terry Brett Caston
Publisher:
ISBN:
Category : Diffusion
Languages : en
Pages :
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Book Description
Due to escalating energy costs and limited fossil fuel resources, much attention has been given to polymer electrolyte membrane (PEM) fuel cells. Gas diffusion layers (GDLs) play a vital role in a fuel cell such as (1) water removal, (2) cooling, (3) structural backing, (4) electrical conduction and (5) transporting gases towards the active catalyst sites where the reactions take place. The power density of a PEM fuel cell in part is dependent upon how uniform the gases are distributed to the active sites. To this end, research is being conducted to understand the mechanisms that influence gas distribution across the fuel cell. Emerging PEM fuel cell designs have shown that higher power density can be achieved; however this requires significant changes to existing components, particularly the GDL. For instance, some emerging concepts require higher through-plane gas permeability than in-plane gas permeability (i.e., anisotropic resistance) which is contrary to conventional GDLs (e.g., carbon paper and carbon cloth), to obtain a uniform gas distribution across the active sites. This is the foundation on which this thesis is centered. A numerical study is conducted in order to investigate the effect of the gas permeability profile on the expected current density in the catalyst layer. An experimental study is done to characterize the effects of the weave structure on gas permeability in woven GDLs. Numerical simulations are developed using Fluent version 6.3.26 and COMSOL Multiphysics version 3.5 to create an anisotropic resistance profile in the unconventional GDL, while maintaining similar performance to conventional GDL designs. The effects of (1) changing the permeability profile in the in-plane and through-plane direction, (2) changing the thickness of the unconventional GDL and (3) changing the gas stoichiometry on the current density and pressure drop through the unconventional GDL are investigated. It is found that the permeability profile and thickness of the unconventional GDL have a minimal effect on the average current density and current density distribution. As a tradeoff, an unconventional GDL with a lower permeability will exhibit a higher pressure drop. Once the fuel cell has a sufficient amount of oxygen to sustain reactions, the gas stoichiometry has a minimal effect on increases in performance. Woven GDL samples with varying tightness and weave patterns are made on a hand loom, and their in-plane and through-plane permeability are measured using in-house test equipment. The porosity of the samples is measured using mercury intrusion porosimetry. It is found that the in-plane permeability is higher than the through-plane permeability for all weave patterns tested, except for the twill weave with 8 tows/cm in the warp direction and 4 tows/cm in the weft direction, which exhibited a through-plane permeability which was 20% higher than the in-plane permeability. It is also concluded that the permeability of twill woven fabrics is higher than the permeability of plain woven fabrics, and that the percentage of macropores, ranging in size from 50-400 ℗æm, is a driving force in determining the through-plane permeability of a woven GDL. From these studies, it was found that the graduated permeability profile in the unconventional GDL had a minimal effect on gas flow. However, a graduated permeability may have an impact on liquid water transport. In addition, it was found that graduating the catalyst loading, thereby employing a non-uniform catalyst loading has a greater effect on creating a uniform current density than graduating the permeability profile.
Author: H. A. Gasteiger
Publisher: The Electrochemical Society
ISBN: 1607682540
Category : Fuel cells
Languages : en
Pages : 2388
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Book Description
Author: Chetan Hire
Publisher:
ISBN:
Category :
Languages : en
Pages : 296
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Book Description
Author: Andrew Kai Cheung Wong
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Liquid water transport and oxygen diffusion within the gas diffusion layer (GDL) play key roles in the performance of a polymer electrolyte membrane (PEM) fuel cell. Understanding how liquid water and oxygen are transported through the GDL is crucial for informing future fuel cell material designs. This thesis contains two studies, one numerical and one experimental, that are focused on liquid water and gas transport in GDLs. The first study is an investigation of how liquid and gas transport in the GDL are affected by increasing microporous layer (MPL) intrusion into the carbon fiber substrate. The second study is an examination of the transport mechanisms in the MPL via the fabrication and testing of GDLs that were entirely composed of MPL (called standalone MPLs). Together, these two studies provide a deeper understanding of how novel applications of the MPL can unlock higher performance in PEM fuel cells.
