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Giles Udel 0060D 13453.Pdf FIRST-PRINCIPLES SIMULATIONS OF ELECTROCATALYTIC ENVIRONMENTS by Stephen Arlow Giles A dissertation submitted to the Faculty of the University of Delaware in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Chemical Engineering Summer 2018 © 2018 Stephen Arlow Giles All Rights Reserved FIRST-PRINCIPLES SIMULATIONS OF ELECTROCATALYTIC ENVIRONMENTS by Stephen Arlow Giles Approved: __________________________________________________________ Eric M. Furst, Ph.D. Chair of the Department of Chemical and Biomolecular Engineering Approved: __________________________________________________________ Babatunde A. Ogunnaike, Ph.D. Dean of the College of Engineering Approved: __________________________________________________________ Douglas J. Doren, Ph.D. Interim Vice Provost for Graduate and Professional Education I certify that I have read this dissertation and that in my opinion it meets the academic and professional standard required by the University as a dissertation for the degree of Doctor of Philosophy. Signed: __________________________________________________________ Dionisios G. Vlachos, Ph.D. Professor in charge of dissertation I certify that I have read this dissertation and that in my opinion it meets the academic and professional standard required by the University as a dissertation for the degree of Doctor of Philosophy. Signed: __________________________________________________________ Yushan Yan, Ph.D. Professor in charge of dissertation I certify that I have read this dissertation and that in my opinion it meets the academic and professional standard required by the University as a dissertation for the degree of Doctor of Philosophy. Signed: __________________________________________________________ Antony N. Beris, Ph.D. Member of dissertation committee I certify that I have read this dissertation and that in my opinion it meets the academic and professional standard required by the University as a dissertation for the degree of Doctor of Philosophy. Signed: __________________________________________________________ Stavros Caratzoulas, Ph.D. Member of dissertation committee I certify that I have read this dissertation and that in my opinion it meets the academic and professional standard required by the University as a dissertation for the degree of Doctor of Philosophy. Signed: __________________________________________________________ Feng Jiao, Ph.D. Member of dissertation committee ACKNOWLEDGMENTS First and foremost, I would like to express my gratitude to my thesis advisors, Professors Dion Vlachos and Yushan Yan. Their patience, wit, and personal guidance have helped me achieve more than I ever thought I could. Their understanding and encouragement throughout the past four and a half years has been unrelenting. It is thanks to them that if given the chance to do everything all over again, I would join their group in a heartbeat. Though not an official “advisor”, Dr. Glen Jenness deserves special acknowledgment for his scientific guidance and friendship. Glen was a postdoc in Dion’s group, and we shared an office together for the first three years I was at Delaware. As someone with zero prior experience in molecular simulations, I was faced with a steep learning curve to begin my Ph.D. research. He essentially functioned as my intellectual lifeline throughout the first couple of years of my research. I cannot repay him, but only say “thank you”. I would like to extend my gratitude to my thesis committee: Prof. Antony Beris, Dr. Stavros Caratzoulas, and Prof. Feng Jiao. Their willingness to meet to discuss and further hone my work is a tribute to their selflessness and intellect. I would also like to extend my gratitude to all Vlachos and Yan group members, past and present, who I have worked with during my time here. These include experimental collaborators, namely Zhongbin Zhuang, Weiqing Zheng, Jie Zheng, Yan Wang, Jared Nash, and Mingchuan Luo, who greatly helped to enrich the quality of my work. I would also like to thank Andrew Tibbits, Ed Schreiner, and v Pierre Desir who, although they did not contribute directly to my work, offered an unparalleled sense of friendship that my work undoubtedly benefited from. Long live Trivia Night at Rooney’s, and Rest in Peace Kildare’s. I hope we will be friends for life. This section would be wholly incomplete without me thanking my parents. I would almost certainly not be obtaining a Ph.D. in Chemical Engineering from the University of Delaware if it were not for my parents making the sacrifice of homeschooling me some twenty years ago. It would have been far easier for them to ship me to public school, and it would have spared Mom from having to deal with my sometimes frequent outbursts. They have continued to make sacrifices and help me in every way they can throughout my undergraduate and graduate career. Those sacrifices are far too many to list here. And finally, to my longtime lover Kate Stanford, here’s to living a bit closer to each other for a change. “Beside you in time”. I love you. “Solve the problem on paper before approaching the machine.” – Bob Ashurst vi TABLE OF CONTENTS LIST OF TABLES ....................................................................................................... xii LIST OF FIGURES ..................................................................................................... xiv ABSTRACT .............................................................................................................. xxix Chapter 1 INTRODUCTION .............................................................................................. 1 1.1 Motivation ................................................................................................. 1 1.1.1 Fuel cells in the renewable energy landscape ................................ 1 1.1.2 Comparison of proton and hydroxide exchange membrane fuel cells ................................................................................................ 1 1.2 Fundamentals of Modeling Electrochemical Hydrogen Oxidation ........... 5 1.2.1 Transition state theory approach of reaction kinetics .................... 5 1.2.2 Butler-Volmer model of electrode kinetics ................................... 5 1.2.3 Standard and reversible hydrogen electrodes: a choice of reference ........................................................................................ 8 1.3 Current Research ..................................................................................... 10 1.3.1 Hydrogen oxidation reaction: state of the field and outlook ....... 10 1.4 Dissertation Scope and Overview ........................................................... 12 2 NICKEL SUPPORTED ON NITROGEN-DOPED CARBON NANOTUBES AS HYDROGEN OXIDATION REACTION CATALYST IN ALKALINE ELECTROLYTE ................................................................... 14 2.1 Introduction ............................................................................................. 14 2.2 Methods ................................................................................................... 16 2.2.1 Experiment .................................................................................. 16 2.2.1.1 Synthesis of nickel-based composite catalyst ............... 16 vii 2.2.1.2 Physical characterization .............................................. 17 2.2.1.3 Electrochemical tests .................................................... 17 2.2.2 Theoretical ................................................................................... 18 2.2.2.1 Computational methodology ........................................ 18 2.3 Results ..................................................................................................... 19 2.3.1 Catalyst synthesis and characterization ....................................... 19 2.3.2 Electrochemical HOR performance ............................................ 21 2.3.3 Theoretical Investigation ............................................................. 24 2.4 Conclusions ............................................................................................. 31 2.5 Acknowledgements ................................................................................. 31 3 EFFECT OF SUBSTITUTIONALLY DOPED GRAPHENE ON THE ACTIVITY OF NANOPARTICLE METAL CATALYSTS FOR THE HYDROGEN OXIDATION REACTION ....................................................... 33 3.1 Introduction ............................................................................................. 33 3.2 Methods ................................................................................................... 35 3.2.1 Model systems of interest ............................................................ 35 3.2.2 Calculations of hydrogen binding energy and HOR activity ...... 37 3.2.3 Principal component analysis of reactivity trends ....................... 39 3.2.4 Size-dependent activity model .................................................... 39 3.2.5 Electronic structure calculations .................................................. 42 3.3 Results ..................................................................................................... 42 3.3.1 Effect of pristine graphene on supported nanoparticles .............. 42 3.3.2 Effect of doped graphene on supported nanoparticles................. 43 3.3.3 Site heterogeneity of the hydrogen binding energy and exchange current density ............................................................. 46 3.3.4 Relative importance of differences
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