Polyaniline Based Nanofibers for Energy Storage and Conversion Devices A Thesis Submitted to the Faculty of Drexel University by Silas K. Simotwo in partial fulfillment of the requirements for the degree of Doctor of Philosophy June 2017 ii ©Copyright 2017 Silas K. Simotwo. All Rights Reserved iii DEDICATIONS I dedicate this thesis to my family. My father and my mother, Mr. Simatwa Kitoo and Mrs. Difina Simatwa iv Acknowledgements I would like to express my sincere gratitude to my academic advisor, Professor Vibha Kalra for accepting me into her lab. None of this would have been possible without her positivity, unrelenting support, guidance, motivation and patience over the last 5 years of my doctoral program. I have learnt a lot from her regarding self-drive and diligence, and she is a great example for me to follow in my future endeavors. I would also like to thank all the members of my dissertation committee, Prof. Jason Baxter, Prof. Kenneth Lau, Prof. Caroline Schauer and Prof. Christopher Li for their insightful feedbacks on my dissertation. I would also like to thank our collaborators: Dr. Chinnam Parameswara and Prof. Stephanie Wunder (Temple University), Dr. Ulises Martinez and Dr. Gautam Gupta, (Los Alamos National Lab), and Prof Kenneth Lau, Yuriy Smolin and Xiaobo Li (Drexel University). It was truly a pleasure working with them. I would like to acknowledge Ed Basgall, Dmitri Barbash, Katie Van Aken and Muhammad Boota for helping me in conducting various characterizations that helped me in conducting my research work. I would also like to acknowledge Prof. Giusseppe Palmese for allowing me to use equipment in his lab. I am extremely grateful to all the former and current members of Kalra research group, Dr. Chau Tran, Dr. Richa Singhal, Dr. Arvinder Singh, Caitlin Dillard, Rahul Pai, Chris Delre, Daniel Lawrence, Alda Kapllani, Ayda Raffie and Amir Hegazy for their friendship, help, and insightful discussions. I am also thankful to the staff members, Andrea, Jennifer for being so nice, and helping me out whenever I needed them. Most importantly, I wish to acknowledge my parents, my sisters and brothers, and all my friends for their patience, love, and endless support. I could not have done this without them. v TABLE OF CONTENTS List of Tables ............................................................................................................................................... ix List of Figures ............................................................................................................................................... x Abstract ....................................................................................................................................................... xiv vi CHAPTER 1. INTRODUCTION................................................................................................... 1 1.1 Energy Storage and Conversion Devices. ........................................................................ 1 1.2 Traditional Capacitors ...................................................................................................... 3 1.3 Supercapacitors ................................................................................................................ 4 1.3.1 Categories of supercapacitors ................................................................................... 5 1.3.1.1 Electrochemical double layer supercapacitors .................................................. 5 1.3.1.2 Pseudocapacitors ............................................................................................... 7 1.3.2 Electrode materials for supercapacitor ...................................................................... 8 1.3.2.1 Carbon ............................................................................................................... 8 1.3.2.2 Pseudocapacitive/redox Materials ..................................................................... 8 1.3.3 Electrolyte for supercapacitors ................................................................................. 9 1.4 Fuel Cells........................................................................................................................ 11 1.5 Electrospinning............................................................................................................... 13 1.6 Polyaniline ...................................................................................................................... 14 1.6.1 Literature review on polyaniline ............................................................................. 15 1.6.1.1 PANI-based Composites as Supercapacitor Cathodes .................................... 15 1.6.1.2 Pure PANI based Supercapacitor .................................................................... 16 1.6.1.3 Electrolytes for PANI based supercapacitors .................................................. 17 1.7 Summary on polyaniline based electrochemical devices. .............................................. 18 1.8 Objectives ....................................................................................................................... 19 CHAPTER 2. Electrospun Polyaniline for Supercapacitors ..................................................... 20 2.1 Introduction .................................................................................................................... 20 2.2 Experimental Methods and Materials ............................................................................ 22 2.2.1 Fabrication of PANI and PANI-CNT nanofibers. .................................................. 22 2.2.2 Electrochemical testing and morphological characterization. ................................ 23 2.3 Results and Discussion ................................................................................................... 25 2.3.1 Nanofibers characterization. ................................................................................... 25 2.4 Conclusion ...................................................................................................................... 36 CHAPTER 3. Asymmetric Supercapacitor Based on Polyaniline-Coated Carbon Nanofibers 37 3.1 Introduction .................................................................................................................... 37 vii 3.2 Experimental techniques ................................................................................................ 40 3.2.1 Electrode preparations. ........................................................................................... 40 3.2.2 Spectroscopic Characterization ............................................................................... 41 3.3 Results and Discussion ................................................................................................... 42 3.3.1 Three-electrode tests: .............................................................................................. 43 Full Cell: Asymmetric supercapacitor ................................................................................... 46 3.3.1.2 In Situ infrared spectroscopy: .......................................................................... 49 3.4 Conclusion. ..................................................................................................................... 52 CHAPTER 4. Redox Mechanisms of Polyaniline in Protic Ionic Liquid ................................. 53 4.1 Introduction .................................................................................................................... 53 4.2 Experiment Section. ....................................................................................................... 55 4.2.1 Synthesis of PILs. ................................................................................................... 55 4.2.2 Synthesis of polyaniline. ......................................................................................... 56 4.2.3 Characterization techniques. ................................................................................... 56 4.3 Results and Discussions. ................................................................................................ 58 4.4 Conclusion. ..................................................................................................................... 61 CHAPTER 5. Co-electrospun Nafion and Polyaniline for Fuel Cell Electrodes Application 62 5.1 Introduction .................................................................................................................... 62 5.2 Experimental Method ..................................................................................................... 64 5.2.1 Nanofiber Fabrication ............................................................................................. 65 5.2.2 Nanofiber Characterization ..................................................................................... 65 5.2.3 Water uptake and Conductivity .............................................................................. 66 5.3 Results and discussion .................................................................................................... 67 5.3.1 Morphology of electrospun nanofibers ................................................................... 67 5.3.2 XRD and FTIR characterization ............................................................................. 72 5.3.3 Impedance study ....................................................................................................