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Durable High Surface Area Electrodes for Rechargeable Zinc Air Batteries
Durable High Surface Area Electrodes for Rechargeable Zinc Air Batteries by Raihan Ahmed A thesis presented to the University of Waterloo in fulfillment of the thesis requirement for the degree of Master of Applied Science in Chemical Engineering Waterloo, Ontario, Canada, 2015 © Raihan Ahmed 2015 Author’s Declaration I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted by my examiners. I understand that my thesis may be made electronically available to the public. ii Abstract The fast growth in technology has led to an increase in demand for convenient storage of energy, primarily rechargeable batteries. People have shown significant interest in metal air batteries throughout history due to their high energy storage capacities, safety, and low cost. These batteries do not require the oxygen, one of their constituent fuels, to be stored inside the cell leading to high volumetric capacities. This is achievable due to the utilization of a unique gas diffusion electrode system that has a complex three phase interface regime. One of the safest and cheapest from the metal air family is the zinc air battery, zinc being one of the most abundant metals on earth. However, researchers have come across various challenges when dealing with these batteries and some of them include sluggish reaction rates, slow gas diffusion rates, and cell material degradation leading to poor power densities and charge-discharge cyclability. This work will address some of these issues via electrode and cell design optimization utilizing some of the proprietary technologies developed in the Applied Nanomaterials and Clean Energy Laboratory. -
Zinc Electrode Shape-Change in Secondary Air Batteries: a 2D Modeling Approach
Zinc Electrode Shape-Change in Secondary Air Batteries: A 2D Modeling Approach Tobias Schmitta,b,c, Tobias Arltd, Ingo Mankee, Arnulf Latza,b,c, Birger Horstmanna,b,c,∗ aGerman Aerospace Center, Pfaffenwaldring 38-40, 70569 Stuttgart, Germany bHelmholtz Institute Ulm, Helmholtzstraße 11, 89081 Ulm, Germany cUlm University, Institute of Electrochemistry, Albert-Einstein-Allee 47, 89069 Ulm, Germany dTechnical University of Berlin, Material Sciences and Technology, Hardenbergstraße 36, 10623 Berlin, Germany eHelmholtz Center for Materials and Energy, Hahn-Meitner-Platz 1, 14109 Berlin, Germany Abstract Zinc-air batteries offer large specific energy densities, while relying on abundant and non-toxic materials. In this paper, we present the first multi-dimensional simulations of zinc-air batteries. We refine our existing theory-based model of secondary zinc-air systems. The model comprises thermodynamically consistent multi-species transport in alkaline electrolytes, formation and disso- lution of metallic zinc and passivating zinc oxide, as well as multi-phase coexistence in gas diffusion electrodes. For the first time, we simulate zinc shape-change during battery cycling by modeling convection of zinc solids. We validate our model with in-situ tomography of commercial button cells. Two-dimensional volume-averaged simulations of cell voltage and zinc electrode morphology during discharge agree with these measurements. Thus, we can study how electrolyte carbonation limits shelf-life and how zinc shape-change limits cycle-life. The charging current is found to be the major contributor to cycle-life limitations. Finally, we optimize initial anode structure and charge-discharge protocols for improved performance and cycle-ability. Keywords: secondary zinc-air battery, aqueous alkaline electrolyte, simulation and validation, x-ray tomography, zinc shape-change 1. -
Development of Novel Thin Membrane Electrode Assemblies (Meas) for High-Efficiency Energy Storage
University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Doctoral Dissertations Graduate School 5-2018 Development of Novel Thin Membrane Electrode Assemblies (MEAs) for High-Efficiency Energy Storage Zhenye Kang University of Tennessee, [email protected] Follow this and additional works at: https://trace.tennessee.edu/utk_graddiss Recommended Citation Kang, Zhenye, "Development of Novel Thin Membrane Electrode Assemblies (MEAs) for High-Efficiency Energy Storage. " PhD diss., University of Tennessee, 2018. https://trace.tennessee.edu/utk_graddiss/4863 This Dissertation is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a dissertation written by Zhenye Kang entitled "Development of Novel Thin Membrane Electrode Assemblies (MEAs) for High-Efficiency Energy Storage." I have examined the final electronic copy of this dissertation for form and content and recommend that it be accepted in partial fulfillment of the equirr ements for the degree of Doctor of Philosophy, with a major in Mechanical Engineering. Feng-Yuan Zhang, Major Professor We have read this dissertation and recommend its acceptance: Lloyd M. Davis, Matthew M. Mench, Zhili Zhang Accepted for the Council: Dixie L. Thompson Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) Development of Novel Thin Membrane Electrode Assemblies (MEAs) for High-Efficiency Energy Storage A Dissertation Presented for the Doctor of Philosophy Degree The University of Tennessee, Knoxville Zhenye Kang May 2018 Copyright © 2018 by Zhenye Kang. -
Gortex-Based Gas Diffusion Electrodes with Unprecedented Resistance to Flooding and Leaking Prerna Tiwari University of Wollongong, [email protected]
University of Wollongong Research Online Australian Institute for Innovative Materials - Papers Australian Institute for Innovative Materials 2018 Gortex-Based Gas Diffusion Electrodes with Unprecedented Resistance to Flooding and Leaking Prerna Tiwari University of Wollongong, [email protected] George Tsekouras University of Wollongong, [email protected] Gerhard F. Swiegers University of Wollongong, [email protected] Gordon G. Wallace University of Wollongong, [email protected] Publication Details Tiwari, P., Tsekouras, G., Swiegers, G. F. & Wallace, G. G. (2018). Gortex-Based Gas Diffusion Electrodes with Unprecedented Resistance to Flooding and Leaking. Acs Applied Materials & Interfaces, 10 (33), 28176-28186. Research Online is the open access institutional repository for the University of Wollongong. For further information contact the UOW Library: [email protected] Gortex-Based Gas Diffusion Electrodes with Unprecedented Resistance to Flooding and Leaking Abstract A significant and long-standing problem in electrochemistry has demanded the need for gas diffusion electrodes that are "flood-proof" and "leak-proof" when operated with a liquid electrolyte. The bsa ence of a solution to this problem has, effectively, made it unviable to use gas diffusion electrodes in many electrochemical manufacturing processes, especially as "gas-depolarized" counter electrodes with significantly decreased energy consumption. In this work, Gortex membranes (also known as expanded PTFE or ePTFE) have been studied as novel, leak-proof substrates for gas diffusion electrodes [PTFE = poly(tetrafluoroethylene)]. We report the fabrication, characterization, and operation of gas diffusion electrodes comprising finely pored Gortex overcoated with 10% Pt on Vulcan XC72, PTFE binder, and a fine Ni mesh as a current carrier. -
Simplified Gas Diffusion Electrode Method for Proton Exchange Membrane Water Electrolysis with a Ultralow Pt Loading
Int. J. Electrochem. Sci., 15 (2020) 2191 – 2204, doi: 10.20964/2020.03.14 International Journal of ELECTROCHEMICAL SCIENCE www.electrochemsci.org Short Communication Simplified Gas Diffusion Electrode Method for Proton Exchange Membrane Water Electrolysis with a ultralow Pt loading Xiaofeng Xie, Shusheng Chen, Yuanquan Zhou, Xiaohong Hu* Hubei Key Lab of Electrochemical Power Source, College of Chemistry and Molecular Sciences, Wuhan University. Wuhan Hubei, 430072, China *E-mail: [email protected] Received: 14 October 2019 / Accepted: 11 December 2019 / Published: 10 February 2020 Proton electrolyte membrane water electrolysis is a promising choice of hydrogen energy while limited by the high cost. Low Pt loading and large-scale application are practical for economic consideration. Here we replace the typical hydrophobic agent polytetrafluoroethylene (PTFE) with commercial fluorinated carbon (CFx) to fabricate hydrogen evolution reaction electrodes with a simplified gas diffusion electrode method. The Pt loading can be reduced as low as 0.03 mg cm-2 without performance loss, and the electrode fabrication method is easy for mass production. Cyclic voltammetry shows CFx electrode has a high Pt Electrochemical surface area (ECSA) as much as 321 m2 g-1, and larger than that of PTFE electrode, the Pt utilization increases 12%. Besides, scanning electron microscopy and pore analysis indicate the excellent performance of CFx electrode is related to the more reasonable three- phase boundaries, especially for the improved proton transfer. In addition, the performance differs with the ratio of CFx and content of CFx. We believe the application of CFx in proton exchange membrane water electrolysis has great economic potential due to the ultralow Pt consumption and easy electrode fabrication process. -
Design of Gas Diffusion Electrodes Using Nanocarbon M
Available online at www.sciencedirect.com Journal of Power Sources 176 (2008) 494–498 Short communication Design of gas diffusion electrodes using nanocarbon M. Soehn a,∗, M. Lebert b, T. Wirth c, S. Hofmann c, N. Nicoloso a a TU Darmstadt, Department of Renewable Energy, Landgraf-Georg-Str. 4, D-64283 Darmstadt, Germany b Max-Planck-Institute for Solid State Research, Heisenbergstr. 1, D-70569 Stuttgart, Germany c University of Cambridge, Department of Engineering, JJ Thomson Avenue, Cambridge CB2 1PZ, UK Available online 2 September 2007 Abstract Two types of gas diffusion electrodes (GDE) with nanocarbon as structural component have been prepared and characterised by TEM, SEM, Raman, conductivity studies and fuel cell testing. The first one combines the well-known properties of carbon cloth and the advantages of carbon nanotubes directly grown on the fibre surface. The second one uses the buckypaper preparation technique which allows a flexible design of layer-type GDEs with tuneable properties (wetting behaviour, catalyst concentration) or gradient materials. Pt catalyst particles are introduced into the (porous) nanocarbon network in a controlled manner by wet- or dry-chemical platinisation. Appropriate particle size (1.4–5 nm) and distribution (0.2–0.4 mg cm−2) are proven by TEM and XRF analysis. The performance of the GDE at high temperature has been tested in a PAFC showing a peak power density of about 220 mW cm−2 at 150 ◦C. © 2007 Elsevier B.V. All rights reserved. Keywords: Carbon nanotubes; Nanocarbon; Electrocatalysis; PAFC 1. Introduction as efficient catalysts for the oxidation of hydrogen (H2 + − − 2− 2H + 2e ) and reduction of oxygen ((1/2)O2 + 2e 0 ), Amorphous carbon (carbon black, carbon fibres) is com- are introduced into the porous carbon matrix by electrochemical monly used in heterogeneous catalysis as easily processable, means or reductive treatment of non-metallic Pt-solutions. -
Cathode Development for Alkaline Fuel Cells Based on a Porous Silver Membrane
*Manuscript text (double-spaced) Click here to view linked References Cathode development for Alkaline Fuel Cells based on a Porous Silver Membrane Abstract: Porous silver membranes were investigated as potential substrates for alkaline fuel cell cathodes by the means of polarisation curves and electrochemical impedance spectroscopy measurements. The silver membranes provide both electrocatalytic function, mechanical support and a means of current collection. Improved performance, compare to a previous design, was obtained by increasing gas accessibility (using Teflon AF instead of PTFE suspension) and by adding a catalyst (MnO 2 or Pt) in the membrane structure to increase the cathode activity. This new cathode design performed significantly better (~ 55 mA cm -2 at 0.8 V, ~295 mA cm -2 at 0.6 V and ~630 mA cm -2 at 0.4 V versus RHE) than the previous design (~ 30 mA cm -2 at 0.8 V, ~250 mA cm -2 at 0.6 V and ~500 mA cm -2 at 0.4 V) in the presence of 6.9 M KOH and oxygen (1 atm(abs)) at room temperature. The hydrophobisation technique of the porous structure and the addition of an extra catalyst appeared to be critical and necessary to obtain high performance. A passive air-breathing hydrogen- air fuel cell constructed from the membranes achieves a peak power density of 65 mW cm -2 at 0.40 V cell potential when operating at 25 oC showing a 15 mW cm -2 improvement compare to the previous design. Keywords: Alkaline fuel cell; gas diffusion electrode; cathode; manganese oxide; silver membrane. -
Impedance of an Oxygen Reducing Gas-Diffusion Electrode VT Cd
Impedance of an Oxygen Reducing Gas-Diffusion Electrode Dietrich Wabner*, Rudolf Holze, Peter Schmittinger Arbeitsgruppe Angewandte Elektrochemie im Institut für Anorganische Chemie der Technischen Universität München und Institut für Physikalische Chemie der Universität Bonn Dedicated to Professor Dr. Wolf Vielstich on the occasion of his 60th birthday Z. Naturforsch. 39b, 157—162 (1984); eingegangen am 24. August 1983 Nernst-Impedance, Fuel Cell Electrode, Oxygen Reduction, Gas Diffusion Electrode, Teflon Bonded Electrode The impedance of teflon bonded electrodes was measured in the frequency domain. These electrodes based on activated carbon as electrocatalyst were developed for fuel cell applications. When feeding the electrode with air or oxygen the impedance spectra could be explained by two Nernst diffusion processes and a small charge transfer process. Two methods for separating the measured impedance into partial impedances related to differ ent steps of the electrode reaction are presented. A least square fit procedure is described which has been applied successfully to the impedance analysis of porous electrodes. List of symbols 1. Introduction Symbol Dimension The measurement of the electrode impedance is a A diffusion factor VT c concentration of diffusing species at mol/dm3 useful method to investigate the kinetics of electrode electrode surface processes. With this method it is possible in many cD double layer capacity mF/cm2 cases to identify the processes, e.g. diffusion, ad d diffusion layer thickness ^m D diffusion coefficient cm2/s sorption or heterogeneous reaction of products and f frequency Hz reactands, which cause the total electrode overpo F Faraday constant As/mol tential. The overpotential of the working electrode current density i mA/cm2 can be separated into parts associated with these pro Im(Z) imaginary part of the complex Q or Q • cm impedance Z cesses. -