scholarly journals Investigation of IrO2/Pt Electrocatalysts in Unitized Regenerative Fuel Cells

2011 ◽  
Vol 2011 ◽  
pp. 1-5 ◽  
Author(s):  
V. Baglio ◽  
C. D'Urso ◽  
A. Di Blasi ◽  
R. Ornelas ◽  
L. G. Arriaga ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Reaction Rate ◽  
Catalytic Properties ◽  
Reduction Process ◽  
Water Electrolysis ◽  
Gas Diffusion ◽  
Diffusion Characteristics ◽  
Pt Electrocatalysts ◽  
Diffusion Properties

IrO2/Pt catalysts (at different concentrations) were synthesized by incipient wetness technique and characterized by XRD, XRF, and SEM. Water electrolysis/fuel cell performances were evaluated in a 5 cm2single cell under Unitized Regenerative Fuel Cell (URFC) configuration. The IrO2/Pt composition of 14/86 showed the highest performance for water electrolysis and the lowest one as fuel cell. It is derived that for fuel cell operation an excess of Pt favours the oxygen reduction process whereas IrO2promotes oxygen evolution. From the present results, it appears that the diffusion characteristics and the reaction rate in fuel cell mode are significantly lower than in the electrolyser mode. This requires the enhancement of the gas diffusion properties of the electrodes and the catalytic properties for cathode operation in fuel cells.

Effect of Vibration on the Liquid Water Transport of PEM Fuel Cells

2009 ◽  
Author(s):  
Luis Breziner ◽  
Peter Strahs ◽  
Parsaoran Hutapea
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Water Transport ◽  
Liquid Water ◽  
Pem Fuel Cells ◽  
Gas Diffusion ◽  
Cell Performance ◽  
Sinusoidal Vibration ◽  
Fuel Cell Performance ◽  
Liquid Water Transport

The objective of this research is to analyze the effects of vibration on the performance of hydrogen PEM fuel cells. It has been reported that if the liquid water transport across the gas diffusion layer (GDL) changes, so does the overall cell performance. Since many fuel cells operate under a vibrating environment –as in the case of automotive applications, this may influence the liquid water concentration across the GDL at different current densities, affecting the overall fuel cell performance. The problem was developed in two main steps. First, the basis for an analytical model was established using current models for water transport in porous media. Then, a series of experiments were carried, monitoring the performance of the fuel cell for different parameters of oscillation. For sinusoidal vibration at 10, 20 and 50Hz (2 g of magnitude), a decrease in the fuel cell performance by 2.2%, 1.1% and 1.3% was recorded when compared to operation at no vibration respectively. For 5 g of magnitude, the fuel cell reported a drop of 5.8% at 50 Hz, whereas at 20 Hz the performance increased by 1.3%. Although more extensive experimentation is needed to identify a relationship between magnitude and frequency of vibration affecting the performance of the fuel cell as well as a throughout examination of the liquid water formation in the cathode, this study shows that sinusoidal vibration, overall, affects the performance of PEM fuel cells.

Fluorescence Microscopy for the Measurement of the Surface Properties of the Gas Diffusion Layers of Fuel

2010 ◽  
Author(s):  
Brooks Friess ◽  
Mina Hoorfar
Keyword(s):  
Water Management ◽  
Fuel Cells ◽  
Fuel Cell ◽  
Fluorescence Microscopy ◽  
Pem Fuel Cells ◽  
Gas Diffusion ◽  
Experimental Methodology ◽  
Test Fluid ◽  
Average Height ◽  
Wetted Area

One of the major problems of current proton exchange membrane (PEM) fuel cells is water management. The gas diffusion layer (GDL) of the fuel cell plays an important role in water management since humidification and water removal are both achieved through the GDL. Various numerical models developed to illustrate the multiphase flow and transport in the fuel cell require the accurate measurement of the GDL properties (wettability and surface energy). In a recent study, the capillary penetration technique has been used to measure indirectly the wettability of the GDL based on the experimental height penetration of the sample liquid into the porous sample. In essence, a high resolution microscope/camera was used to detect the rate of penetrated height into the sample GDL. The shortcoming of this type of visualization is that it can only be used for thin hydrophilic GDL samples with zero Teflon loadings. For the thick and high Teflon loading GDLs, there is not enough contrast to detect the height of the penetrated liquid. In the real fuel cells, the GDLs are made of the micro-porous and macro-porous layers with an optimum Teflon loading. Therefore, it is required to develop a new experimental methodology capable of detecting the rate of penetration and as a result the wettability of GDLs samples used in fuel cells. In this paper, the fluorescence microscopy technique is integrated into the experimental setup of the capillary penetration method to improve the contrast between the wetted and non-wetted area. The fluorescence setup uses a powder die, dissolved in the test fluid, which is excited by a concentrated ultraviolet light illuminated in the vertical manner. To acquire the profile images of the penetrated liquid, an optical mirror was used. This new setup has the added advantage of providing a visual representation of the different regimes of penetration (e.g., the fingering effect reported for the pathways of the liquid penetrated into the GDLs) that are defined by the capillary number and mobility ratio of each fluid. Since the GDL samples used in this study are relatively hydrophobic (e.g., with 40% Teflon loadings), the pattern of liquid penetration is not uniform. Thus, an image analysis program was developed to determine the average height of penetration based on the area under the entire wetted area. The general Washburn equation was then used to fit the extracted height data and provide the average internal contact angle for each test liquid.

Computational Modelling and Simulation of Proton-Exchange Membrane Fuel Cells (Keynote)

2002 ◽  
Author(s):  
N. Djilali ◽  
T. Berning
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Proton Exchange Membrane ◽  
Transport Phenomena ◽  
Computational Modelling ◽  
Ambient Air ◽  
Gas Diffusion ◽  
Transport Processes ◽  
Proton Exchange ◽  
Exchange Membrane

Fuel cells (FC’s) are electrochemical devices that convert directly into electricity the chemical energy of reaction of a fuel (usually hydrogen) with an oxidant (usually oxygen from ambient air). The only by-products in a hydrogen fuel cell are heat and water, making this emerging technology the leading candidate for quiet, zero emission energy production. Several types of fuel cell are currently undergoing intense research and development for applications ranging from portable electronics and appliances to residential power generation and transportation. The focus of this lecture is Proton-Exchange Membrane Fuel Cells (PEMFC’s). An electrolyte consisting of a “solid” polymer membrane, low operating temperatures (typically below 90 °C) and a relatively simple design combine to make PEMFC’s particularly well suited to automotive and portable applications. The operation of a fuel cell relies on electrochemical reactions and an array of coupled transport phenomena, including multi-component gas flow, two phase-flow, heat and mass transfer, phase change and transport of charged species. The transport processes take place in variety of media, including porous gas diffusion electrodes and polymer membranes. The fuel cell environment makes it impossible to measure in-situ the quantities of interest to understand and quantify these phenomena, and computational modelling and simulations are therefore poised to play a central role in the development and optimization of fuel cell technology. We provide an overview of the role of various transport phenomena in fuel cell operation and some of the physical and computational modelling challenges they present. The processes will be illustrated through examples of multi-dimensional numerical simulations of Proton-Exchange Membrane Fuel Cells. We close with a perspective on some of the many remaining challenges and future development opportunities.

scholarly journals An Investigation of Direct Hydrocarbon (Propane) Fuel Cell Performance Using Mathematical Modeling

2018 ◽  
Vol 2018 ◽  
pp. 1-18
Author(s):  
Bhavana Parackal ◽  
Hamidreza Khakdaman ◽  
Yves Bourgault ◽  
Marten Ternan
Keyword(s):  
Fuel Cells ◽  
Current Density ◽  
Reaction Rate ◽  
Gas Diffusion ◽  
Proton Exchange ◽  
Polarization Curves ◽  
Limiting Current ◽  
Fuel Cell Performance ◽  
Limiting Current Density ◽  
Current Densities

An improved mathematical model was used to extend polarization curves for direct propane fuel cells (DPFCs) to larger current densities than could be obtained with any of the previous models. DPFC performance was then evaluated using eleven different variables. The variables related to transport phenomena had little effect on DPFC polarization curves. The variables that had the greatest influence on DPFC polarization curves were all related to reaction rate phenomena. Reaction rate phenomena were dominant over the entire DPFC polarization curve up to 100 mA/cm2, which is a value that approaches the limiting current densities of DPFCs. Previously it was known that DPFCs are much different than hydrogen proton exchange membrane fuel cells (PEMFCs). This is the first work to show the reason for that difference. Reaction rate phenomena are dominant in DPFCs up to the limiting current density. In contrast the dominant phenomenon in hydrogen PEMFCs changes from reaction rate phenomena to proton migration through the electrolyte and to gas diffusion at the cathode as the current density increases up to the limiting current density.

Characterization of Fuel Cells and Fuel Cell Systems Using Three-Dimensional X-Ray Tomography

2006 ◽  
Vol 4 (1) ◽  
pp. 84-87 ◽  
Author(s):  
Stefan Griesser ◽  
G. Buchinger ◽  
T. Raab ◽  
D. P. Claassen ◽  
Dieter Meissner
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Ionic Conductivity ◽  
First Generation ◽  
Mechanical Stability ◽  
Three Dimensional ◽  
Gas Diffusion ◽  
Critical Parameters ◽  
Electrode Layer ◽  
X Ray

Three dimensional (3D) computer aided X-ray tomography (CT) has proven to be an extremely useful tool in developing our own as well as in examining commercially available solid oxide fuel cells. The results of 3D-CT measurements became very important for understanding the functionality of our first generation and improving the development of our second fuel cell generation. Also geometrical measurements, especially the roundness and the straightness of the tube, can be evaluated, both critical parameters when the stack is heated and mechanical stress has to be avoided. By using this technique the structure of the first generation cells proved to be of insufficient quality. Problems like the variation in thickness of the electrolyte tube as well as the homogeneity in thickness of the electrodes deposited can easily be detected by this nondestructive technique. Microscopic investigations of this problem of course provide equal results, but only after cutting the samples in many slices and many single measurements of different areas of the fuel cell. Using cells with inhomogeneous thickness of course results in drastic variations of the current densities along a single cell. Electrolyte layers that are too thick will result in power loss due to the increased resistance in the ionic conductivity of the electrolyte. If the electrolyte of an electrolyte supported cell is too thin, this can cause mechanical instability. Problems can also occur with the leak tightness of the fuel cell tube. Gas diffusion through the electrode layer can become a problem when the thickness of the electrode layer is too high. On the other hand, if the layers are too thin, the result can be a discontinuous layer, leading to a high electrical series resistance of the electrode. Besides determining the thickness variations also the porosity of the electrolyte needs careful attention. Larger cavities or shrink holes form insulating islands for the ion-stream and are therefore limiting the ionic conductivity. They are also diminishing the mechanical stability and provide problems for depositing a closed electrode film in electrode supported cells.

A Feasibility Study of Ribbon Architecture for PEM Fuel Cells

2010 ◽  
Vol 7 (5) ◽  
Author(s):  
Daniel F. Walczyk ◽  
Jaskaran S. Sangra
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
High Volume ◽  
Pem Fuel Cells ◽  
Gas Diffusion ◽  
Open Circuit ◽  
Membrane Electrode ◽  
Fixture Design ◽  
Design Development ◽  
Test Fixture

The feasibility of an alternative fuel cell architecture, called a ribbon membrane electrode assembly (MEA), is demonstrated for low-temperature polymer electrolyte membrane (PEM) fuel cells used in portable power applications by comparing it to a traditional bipolar “stack” architecture. A ribbon MEA consists of adjacent PEM cells sharing a common gas diffusion layer to allow for lateral electrical current flow and an integral gas-tight, conductive interconnect/seal, where adjacent cells meet to prevent reactant gas leakage. The resulting lateral arrangement of MEAs can be used to supply all MEAs simultaneously instead of individual bipolar plates with flow fields for a stack. A pair of two-cell ribbon MEAs, with and without an interconnect/seal, were designed, prototyped, and sealed by thermal pressing. The MEAs were clamped in a two-piece box fixture to provide reactant gases on the anode and cathode sides, hooked to a fuel cell (FC) test stand and yielded an open circuit voltage (OCV) of 1.43 V with an interconnect/seal and 0.6 V without. A two-cell bipolar stack PEMFC with identical MEA specifications had an OCV of 1.86 V. Polarization curves for the ribbon MEA with interconnect/seal showed the sensitivity of performance to clamping pressure and positioning of the copper current collectors. The ribbon MEA polarization curve was also shifted downward by 0.42 V as compared with that of the traditional stack, and suspected causes (e.g., gas leaking) are attributable to the nonoptimal test fixture design. Hence, the ribbon MEA architecture is shown to be feasible. Future work suggested includes improvements to the test fixture design, development of automated manufacturing capabilities for high volume production, and demonstration of a multicell (>2) ribbon MEA PEMFC design.

scholarly journals High crystallinity design of Ir-based catalysts drives catalytic reversibility for water electrolysis and fuel cells

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Woong Hee Lee ◽  
Young-Jin Ko ◽  
Jung Hwan Kim ◽  
Chang Hyuck Choi ◽  
Keun Hwa Chae ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Catalytic Properties ◽  
Hydrogen Oxidation ◽  
Water Electrolysis ◽  
Oxidation Reactions ◽  
Hydrogen Electrode ◽  
Positive Potential ◽  
Nanoparticle Catalysts ◽  
High Crystallinity ◽  
Hydrogen Evolution Reactions

AbstractThe voltage reversal of water electrolyzers and fuel cells induces a large positive potential on the hydrogen electrodes, followed by severe system degradation. Applying a reversible multifunctional electrocatalyst to the hydrogen electrode is a practical solution. Ir exhibits excellent catalytic activity for hydrogen evolution reactions (HER), and hydrogen oxidation reactions (HOR), yet irreversibly converts to amorphous IrOx at potentials > 0.8 V/RHE, which is an excellent catalyst for oxygen evolution reactions (OER), yet a poor HER and HOR catalyst. Harnessing the multifunctional catalytic characteristics of Ir, here we design a unique Ir-based electrocatalyst with high crystallinity for OER, HER, and HOR. Under OER operation, the crystalline nanoparticle generates an atomically-thin IrOx layer, which reversibly transforms into a metallic Ir at more cathodic potentials, restoring high activity for HER and HOR. Our analysis reveals that a metallic Ir subsurface under thin IrOx layer can act as a catalytic substrate for the reduction of Ir ions, creating reversibility. Our work not only uncovers fundamental, uniquely reversible catalytic properties of nanoparticle catalysts, but also offers insights into nanocatalyst design.

scholarly journals Meta-study Focusing on Abiotic Cells for Human Implants

2016 ◽  
Vol 3 ◽  
pp. 100-112 ◽  
Author(s):  
Mitchell Healey ◽  
Julian Lee
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Microbial Fuel Cells ◽  
Reaction Rate ◽  
Internal Resistance ◽  
Rechargeable Batteries ◽  
Implantable Devices ◽  
Operational Parameters ◽  
Short Lifespan ◽  
Target Glucose

Abstract: Powering implantable devices in human body with a glucose based fuel cell (GFC) offers an alternative to non-rechargeable batteries that typically require routine invasive surgery. There are three main approaches for GFCs to oxidise glucose. Enzymatic Fuel Cells are selective and have a high reaction rate but are unstable as the proteins can denature giving the cell a short lifespan. Microbial Fuel Cells use microbes to break down glucose to produce electrons. However they possess the danger of cell leakages that can introduce the microbes to the patient and risk possible infection. Abiotic Fuel Cells employ inorganic catalysts, typically a noble metal alloy or metallic carbon to oxidise and reduce glucose and oxygen respectively. Abiotic is the safest and most stable of the three but possesses the lowest output due to the electrodes inability to target glucose specifically. This meta-study investigates for Abiotic Glucose Fuel Cell being the most viable candidate of the three for possible use in autonomous medical devices. We will assess current abiotic fuel cells on the thermodynamic parameters of output voltage, current/current density, power density and efficiency. The kinetic parameters of internal resistance and rate at which membranes transport electrons will also be assessed. Operational parameters of lifespan and overall architecture will also be assessed to further understand the conditions and materials these cells were produced.Keywords: Glucose; Fuel Cell; Meta-study; Enzymatic; Microbial; Abiotic; Implantable Devices

scholarly journals An Intelligent Approach for Contact Pressure Optimization of PEM Fuel Cell Gas Diffusion Layers

2020 ◽  
Vol 10 (12) ◽  
pp. 4194
Author(s):  
Yongbo Qiu ◽  
Peng Wu ◽  
Tianwei Miao ◽  
Jinqiao Liang ◽  
Kui Jiao ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Contact Pressure ◽  
Gas Diffusion ◽  
Proton Exchange ◽  
Optimization Approach ◽  
Fe Model ◽  
Latin Hypercube Design ◽  
Agent Model ◽  
Intelligent Approach

The compression of the gas diffusion layer (GDL) greatly affects the electrochemical performance of proton exchange membrane fuel cells (PEMFCs) by means of both the equivalent value and distribution of contact pressure, which depends on the packing manner of the fuel cell. This work develops an intelligent approach for improving the uniformity and equivalent magnitude of contact pressure on GDLs through optimizing the clamping forces and positions on end plates. A finite element (FE) model of a full-size single fuel cell is developed and correlated against a direct measurement of pressure between the GDL and a bipolar plate. Datasets generated by FE simulations based on the optimal Latin hypercube design are used as a driving force for the training of a radial basis function neural network, so-called the agent model. Once the agent model is validated, iterations for optimization of contact pressure on GDLs are carried out without using the complicated physical model anymore. Optimal design of clamping force and position combination is achieved in terms of better contact pressure, with the designed equivalent magnitude and more uniform distribution. Results indicate the proposed agent-based intelligent optimization approach is available for the packing design of fuel cells, stacks in particular, with significantly higher efficiency.

GOLD-PLATED TITANIUM VS CARBON-IMPLANTED TITANIUM AS MATERIAL FOR BIPOLAR PLATES IN PEM FUEL CELLS

2019 ◽  
Vol 26 (08) ◽  
pp. 1950038
Author(s):  
M. S. VLASKIN ◽  
A. V. GRIGORENKO ◽  
E. I. SHKOLNIKOV ◽  
A. S. ILYUKHIN
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Performance Enhancement ◽  
Precious Metals ◽  
Pem Fuel Cells ◽  
Gas Diffusion ◽  
Electrical Performance ◽  
Carbon Ions ◽  
Bipolar Plates ◽  
Gold Plating

Three different types of current-collecting plates for air-hydrogen PEM fuel cell were manufactured and tested: unmodified titanium plates; gold-plated titanium plates and titanium plates treated by carbon ions implantation. It was shown that the applied surface modifications reduce contact resistance between titanium plate and carbon gas diffusion layer. Total ohmic resistance of fuel cell is reduced by 1.8 and 1.4 times in case of gold-plated titanium and carbon-implanted titanium, respectively, in comparison with uncoated titanium. Although gold plating turned out to be more profitable than carbon ion implantation in terms of electrical characteristics, in the last case, the performance enhancement was reached without using precious metals, which at mass production must play more important role. This technology promises to reduce the cost of bipolar plates manufacturing, while maintaining high electrical performance of PEM fuel cells.

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