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Electrodes and Membranes for Alkaline Energy Storage and Conversion Devices University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Doctoral Dissertations Graduate School 12-2018 Electrodes and Membranes for Alkaline Energy Storage and Conversion Devices Asa Logan Roy University of Tennessee, aroy4@vols.utk.edu Follow this and additional works at: https://trace.tennessee.edu/utk_graddiss Recommended Citation Roy, Asa Logan, "Electrodes and Membranes for Alkaline Energy Storage and Conversion Devices. " PhD diss., University of Tennessee, 2018. https://trace.tennessee.edu/utk_graddiss/5312 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 trace@utk.edu. To the Graduate Council: I am submitting herewith a dissertation written by Asa Logan Roy entitled "Electrodes and Membranes for Alkaline Energy Storage and Conversion Devices." 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 Energy Science and Engineering. Thomas A. Zawodzinski, Major Professor We have read this dissertation and recommend its acceptance: Dibyendu Mukherjee, Jagjit Nanda, David L. Wood III 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.) Electrodes and Membranes for Alkaline Energy Storage and Conversion Devices A Dissertation Presented for the Doctor of Philosophy Degree The University of Tennessee, Knoxville Asa Logan Roy December 2018 Copyright © 2018 by Asa Roy All rights reserved. ii Dedication To my wife, Hannah And to my Parents, Will and Daneen iii Acknowledgements I would first like to thank my advisor Dr. Thomas Zawodzinski. For providing me with the opportunity to work on such a wide range of projects, for providing the resources and guidance to complete this work, and for the ability to satisfy my intellectual curiosity, I owe him a great debt of gratitude. I would also like to give deep thanks to Dr. Gabriel Goenaga for training me in numerous experimental techniques, the opportunity to collaborate on various projects, and always being available to lend a helping hand, personally or professionally. I would like to thank my committee members, Dr. Jagjit Nanda, Dr. David Wood, and Dr. Dibyendu Mukherjee. I must also thank the members of the Z group, past and present, for their help in completing this work. Whether this entailed training in new techniques, assistance with experiments, or discussions about research methods or data it has always been a friendly and helpful environment. There are several members of the Z group who I would like to thank in particular. I would like to thank Dr. Shane Foister for his willingness to collaborate on projects and share knowledge. I would like to thank Dr. Sam St. John for his help with various experimental techniques which proved instrumental in this work and his example as a driven researcher. And I would like to thank Dr. Alex Papandrew for his expertise, advice, and example. Finally, I would like to thank my wife, Hannah, for her unwavering support and encouragement throughout my doctoral study. I would not be where I am today without the love and support from my family, my parents, Will and Daneen, my brother, Adam, and my sisters, Randi and Tessa. iv Abstract The high cost of platinum catalysts remains a major limitation to the development of proton exchange membrane fuel cells (PEMFCs). Despite a monumental research effort for platinum group metal free (PGM-free) catalysts, no viable alternative has been found that matches platinum in activity and stability. Further efforts to reduce cost have increased focus on anion exchange membrane fuel cells (AEMFCs) in recent years. Changing the conducting ion from protons in PEMs to hydroxide in AEMs changes the fuel cell environment from acidic to basic. Many PGM-free catalysts show increased activity and stability in basic environments. Considering the promise of AEMFCs a series of systematic studies was conducted on several cell components. The physical and catalytic properties of a family of PGM-free oxygen reduction catalysts was studied through various spectrographic and voltammetric techniques. A thorough study of the catalyst performance in a single cell fuel cell test was conducted, leading to the development of a PGM-free catalyst which matched the performance of platinum. The anode performance was found to be significantly lower than expected. A systematic investigation of AEMFC anodes attributed the poor performance to electrode flooding. Modification of the anode catalyst layer led to improved anode performance to the detriment of the whole-cell performance. These results highlighted the need for a greater level of understanding of water transport in AEMs. To this end, several anion exchange membranes were synthesized and the effect of cation structure on water uptake, conductivity, stability was measured. Additionally, water uptake, conductivity, and the electro-osmotic drag of water were studied in a commercial AEM. The knowledge of oxygen electrodes for AEMFCs was leveraged for the development of rechargeable zinc-air batteries (ZABs). ZABs utilize oxygen from the air as half the battery chemistry to dramatically reduce the size and weight of the cell. Rechargeable ZABs are expected to half energy densities 4-5x higher than lithium ion batteries. However, their development is hindered by zinc dendrite and passivation issues, poor oxygen catalysis, and electrolyte management. In this work, bifunctional oxygen reduction and evolution catalysts and novel anion exchange membrane are studied through ex-situ and in-situ methods. v Table of Contents Introduction ................................................................................................................................... 1 Part 1: Catalysts and Electrodes for Alkaline Fuel Cells and Batteries .................................. 2 Introduction and Background ............................................................................................................... 3 Chapter 1: Platinum-Group Metal Free Oxygen Reduction Catalysts ......................................... 8 Introduction ........................................................................................................................................... 8 Experimental ....................................................................................................................................... 20 Results and Discussion ....................................................................................................................... 23 Conclusion .......................................................................................................................................... 40 Chapter 2: Bifunctional Oxygen Catalysts for Zinc-Air Batteries .............................................. 42 Introduction ......................................................................................................................................... 42 Experimental ....................................................................................................................................... 53 Results and Discussion ....................................................................................................................... 55 Conclusion .......................................................................................................................................... 68 Chapter 3: Reversible Two Electron Oxygen Catalyst ................................................................. 69 Introduction ......................................................................................................................................... 69 Experimental ....................................................................................................................................... 70 Results and Discussion ....................................................................................................................... 71 Conclusions ......................................................................................................................................... 83 Chapter 4: Hydrogen Catalysts and Electrode Structure for AEMFCs ..................................... 84 Introduction ......................................................................................................................................... 84 Experimental ....................................................................................................................................... 86 Results and Discussion ....................................................................................................................... 88 Conclusion .......................................................................................................................................... 97 Part 2: Membranes for Alkaline Fuel Cells and Batteries ...................................................... 99 Introduction and Background ........................................................................................................... 100 Chapter 5: Anion Exchange Membranes for Fuel Cells ............................................................
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