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A Study About Aqueous Reversible Air Electrode- Catalyst, Electrolyte and Structure

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A Study About Aqueous Reversible Air Electrode- Catalyst, Electrolyte and Structure University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Doctoral Dissertations Graduate School 12-2013 A study about aqueous reversible air electrode- Catalyst, Electrolyte and Structure Ming Qi University of Tennessee - Knoxville, [email protected] Follow this and additional works at: https://trace.tennessee.edu/utk_graddiss Part of the Catalysis and Reaction Engineering Commons Recommended Citation Qi, Ming, "A study about aqueous reversible air electrode- Catalyst, Electrolyte and Structure. " PhD diss., University of Tennessee, 2013. https://trace.tennessee.edu/utk_graddiss/2609 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 Ming Qi entitled "A study about aqueous reversible air electrode- Catalyst, Electrolyte and Structure." 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 Chemical Engineering. Thomas A. Zawodzinski, Major Professor We have read this dissertation and recommend its acceptance: Alexander B. Papandrew, Robert M. Counce, Matthew M. Mench Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) A study about aqueous reversible air electrode Catalyst, Electrolyte and Structure A Dissertation presented for the Doctor of Philosophy Degree The University of Tennessee, Knoxville Ming Qi December 2013 ii Copyright © 2013 by Ming Qi All rights reserved. iii Acknowledgements There are many people that I need to appreciate for their help during my graduate school. First, I need to thank my supervisor, Dr. Thomas Zawodzinski, for giving me this opportunity to do this research and a wonderful experience of working in his lab. I also need to thank him for being very patient with my continuous new ideas about my research and always encourage me to explore new things. I also need to thank my committee members, Dr. Mench and Dr. Papandrew, for giving me advice on catalyst preparation and structure design. I also need to thank Dr.Counce for many suggestions about discussion and writing in this thesis. I also need to thank two senior researchers in our group, Dr Gabriel Goenaga and Dr. Shane Foister, for many suggestions to my research. And other graduate students also offer many help, especially Rob Atkinson helped me with XRD and Luke Servedio helped me with my organic electrochemistry. Dr. Jagjit Nanda and Dr. Gabriel Veith also helped me in the aspect of understanding lithium ion battery. For my personal life, I must thank my girlfriend, Yang Li, for being such a good accompany in my life. My life is more colorful because of you. I also need to thank many of my friends here for making my life full of fun. At last, I need to thank TN-Score program for the funding support to make this work possible. iv Abstract Developing a better high energy density rechargeable battery has becoming critically important for several industries. For building such kind of battery, reversible air electrode has been widely accepted as one of the key components. One of the major challenges for reversible air electrode is finding a good bifunctional catalyst to greatly reduce the recharge overpotential and increase the system efficiency. To achieve this goal, a new air battery chemistry based on cobalt salen modified Au catalyst is proposed in this dissertation as a very promising solution. The unique catalytic activity of this catalyst is found to be a two electron reversible ORR in alkaline electrolyte, which is the most reversible air electrode chemistry system known to date. The reaction mechanism of this catalyst is explained by the surface double layer theory. Cobalt salen is believed to locate in the outer Helmholtz layer, inducing Au surface reconstruction and promoting oxygen chemisorption. Temperature and pH are found to be important environmental conditions for controlling the catalyst ORR reversibility. Electropolymerization is found to be a effective method to stabilize the surface modification without jeopardizing catalytic activity. The nano size Au particles are found to be harmful for ORR reversibility because of the stronger peroxide reduction ability. EDTA, as peroxide stabilizer, is found to be an excellent additive to the electrolyte environment. Three new electrochemical systems are proposed according to the catalyst structure on peroxide production and battery application. An energy storage method and flowing cell structure are discussed in detail for applying this catalyst. The influence of the cation to the ORR catalytic activity on noble metal catalyst is also v explained by surface double layer structure, for which the cation proved to have significant influence on the chemisorptions of oxygen containing species. vi Table of Contents Chapter 1 Introduction ..................................................................................................................... 1 1. 1 Energy challenge .................................................................................................................. 1 1. 2 Battery basics ....................................................................................................................... 5 1. 3 Lithium-ion battery ............................................................................................................... 8 1. 4 Alkaline fuel cell .................................................................................................................. 9 1. 5 Oxygen reduction reaction in alkaline solution .................................................................. 12 1. 6 Lithium-air battery.............................................................................................................. 16 1.6.1 Aprotic lithium-air battery ............................................................................................ 17 1.6.2 Aqueous and mix electrolyte lithium-air battery .......................................................... 24 1.6.3 Ionic liquid and solid state lithium-air battery .............................................................. 27 1. 7 Cobalt based catalyst .......................................................................................................... 28 1. 8 The goal and scope of this dissertation ............................................................................... 30 Chapter 2 Experimental Methods .................................................................................................. 34 Chapter 3 Reversible ORR catalyst - I Reaction mechanism ........................................................ 42 3. 1 Background research .......................................................................................................... 42 3.1.1 Quasi-reversible Oxygen reduction reaction on Au (111) ............................................ 42 3.1.2 Oxygen reduction reaction on Au (100) ....................................................................... 44 3.1.3 Surface reconstruction phenomenon on Au electrode .................................................. 47 3.1.4 The influence of Au surface reconstruction to ORR .................................................... 50 3.1.5 Au (111)-like polycrystalline gold electrode ................................................................ 52 3.2 Interaction between cobalt salen and Au in alkaline environment ...................................... 56 3.3 Oxygen reduction reaction on cobalt salen modified Au electrode ..................................... 60 3.4 EC mechansim: catalytic case ............................................................................................. 66 3.5 RDE and RRDE experiment ................................................................................................ 70 3.6 Cobalt salen induced surface reconstruction on Au electrode ............................................. 77 3.7 ORR kinetics and reaction mechanism on cobalt salen modified Au electrode .................. 83 3.8 IR surface characterization on modified electrode .............................................................. 90 Chapter 4 Reversible ORR catalyst -- II Characterization and preparation method ..................... 94 vii 4. 1 Temperature influence on oxygen reduction reaction ........................................................ 94 4.1.1 Base voltammetry of Au (poly) at different temperatures ............................................ 94 4.1.2 Temperature influence on ORR on gold electrode ....................................................... 98 4.1.3 Temperature influence on reversible ORR catalyst .................................................... 100 4. 2 The influence of pH on the reversible ORR catalyst ........................................................ 103 4.3 Peroxide oxidation on cobalt salen modified Au electrode ............................................... 106 4.4 Electropolymerization cobalt salen on polycrystalline Au electrode ................................ 110 4.5 The influence of electropolymerization on catalytic stability ..........................................
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