Design of Novel Titanium Dioxide-Based Multifunctional Electrochemical Cells by Gregory Lui A thesis presented to the University of Waterloo in fulfillment of the thesis requirement for the degree of Doctor of Philosophy in Chemical Engineering (Nanotechnology) Waterloo, Ontario, Canada, 2018 © Gregory Lui 2018 Examining Committee Membership The following served on the Examining Committee for this thesis. The decision of the Examining Committee is by majority vote. External Examiner NAME: Paul Charpentier Title: Professor Department of Chemical and Biochemical Engineering Supervisor(s) NAME: Aiping Yu Title: Associate Professor Department of Chemical Engineering, University of Waterloo NAME: Michael Fowler Title: Professor Department of Chemical Engineering, University of Waterloo Internal Member(s) NAME: William Anderson Title: Professor Department of Chemical Engineering, University of Waterloo NAME: Michael Pope Title: Assistant Professor Department of Chemical Engineering, University of Waterloo Internal-external Member NAME: Siva Sivoththaman Title: Professor Department of Electrical and Computer Engineering, University of Waterloo Other Member(s) n/a ii Author’s Declaration This thesis consists of material all of which I authored or co-authored: see Statement of Contributions included in the 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. iii Statement of Contribution The body of this thesis is based on a combination of published work. Various sections are adapted from the following list of publications. Chapter 4 Lui, G.; Li, G.; Wang, X.; Jiang, G.; Lin, E.; Fowler, M.; Yu, A.; Chen, Z., Flexible, three- dimensional ordered macroporous TiO2 electrode with enhanced electrode–electrolyte interaction in high-power Li-ion batteries. Nano Energy 2016, 24, 72-77. I performed all synthesis experiments with the help of E. Lin. G. Li helped with battery fabrication and testing. X. Wang and G. Jiang helped analyze the data and review the manuscript. Chapter 5 Lui, G.; Jiang, G.; Lenos, J.; Lin, E.; Fowler, M.; Yu, A.; Chen, Z., Advanced Biowaste‐Based Flexible Photocatalytic Fuel Cell as a Green Wearable Power Generator. Advanced Materials Technologies 2017, 2 (3). I performed all synthesis and characterization experiments with the help of E. Lin. G. Jiang helped analyze the data and review the manuscript. J. Lenos helped with device testing. Chapter 6 Lui, G.; Jiang, G.; Fowler, M.; Yu, A.; Chen, Z., A High Performance Waste water-Fed Flow- Photocatalytic Fuel Cell. (submitted to Journal of Power Sources). I performed all synthesis and characterization experiments. G. Jiang provided significant contribution to project direction, helped analyze the data, and reviewed the manuscript. iv Abstract Increasing energy demands as well as the depletion of traditional resources has led to the development and improvement of energy conversion and storage technologies. Today, two major concerns are development of renewable sources of energy and establishing reliable sources of potable water to the meet continually growing demands of our society. One technology that has the potential to address both of these issues is the photocatalyst: a material that is able to use natural light irradiation to drive useful chemical reactions and create electrical power. Photocatalytic materials have already been commercially demonstrated to purify waste water and air pollution under ultraviolet irradiation. However, in a photoelectrochemical cell, photocatalytic applications extended beyond waste water remediation to the production of electricity and alternative fuels such as hydrogen gas. This thesis aims to explore the potential multifunctionality of TiO2 materials and point to applications that extend beyond traditional photocatalysis. Specifically, this work covers the study and design of titanium oxide (TiO2)-based multifunctional electrochemical cells that can simultaneously purify waste water and provide energy in the form of electrical power. First, this thesis explored potential applications for three-dimensional macroporous (3DOM) TiO2 morphologies for electrochemical applications. Although the material was a suitable photocatalyst it was found to be an effective freestanding TiO2 anode on carbon cloth for Li-ion battery applications. The 3DOM TiO2-based anode provided a flexible, free-standing, binder- free, active material with superior power density when compared to other electrode materials in a similar configuration. This work also provided the first instance of the successful application of 3DOM materials on non-planar surfaces. v Commercial TiO2 (P25) was also employed as a photoanode in a flexible photocatalytic fuel cell as a proof-of-concept device that generates electrical power from the photo-degradation of waste sources such as human sweat (as a wearable device) and dye waste (as a flexible water treatment device). This work established the potential application of photocatalysis in wearable technologies and in flexible photocatalytic devices in general. Finally, a burr-like Ag-TiO2 photocatalyst was developed as a photoanode material in a flow- photocatalytic fuel cell for the continuous power generation and photo-degradation of brewery effluent under solar-simulated light. This work explored the effect of Ag loading on photoelectrochemical performance, and demonstrated unprecedented power density of a flow- photocatalytic fuel cell in a continuous flow configuration. vi Acknowledgements I would like to thank my supervisors, Prof. Aiping Yu and Prof. Michael Fowler, for supporting and guiding me throughout my studies, and giving me the freedom to explore and pursue different scientific interests. I would also like to thank Prof. Zhongwei Chen for providing research guidance and lab space throughout my tenure. I would like to acknowledge Dr. Gaopeng Jiang for all of his collaborative efforts and invaluable advice during my research. I would like to thank everyone at the Applied Carbon Nanotechnology Laboratory and Applied Nanomaterials & Clean Energy Laboratory for making the machine work without oil. Thank you Stephanie Lu for being my personal assistant, biggest fan, and best friend, and for doing most of the worrying on my behalf. Thank you to my family – Yvonne, Geoff Ryan, Genny, and Kurt – for taking care of me and keeping me relatively sane for the past n years. Thank you for everything, Dad. Soli Deo gloria. vii Table of Contents Examining Committee Membership ............................................................................................ ii Author’s Declaration ................................................................................................................... iii Statement of Contribution ........................................................................................................... iv Abstract ........................................................................................................................................ v Acknowledgements .................................................................................................................... vii Table of Figures ........................................................................................................................ xiii Table of Tables ......................................................................................................................... xix 1.0 Introduction ............................................................................................................................ 1 1.1 Objectives ........................................................................................................................... 3 1.2 Thesis Organization ........................................................................................................... 4 2.0 Literature Review .................................................................................................................. 6 2.1 Semiconductor Theory ....................................................................................................... 6 2.1.1 Doping ......................................................................................................................... 7 2.1.2 Semiconductors in Heterogeneous Systems ................................................................ 8 2.2 Titanium Dioxide (TiO2) as a Photocatalytic Material .................................................... 10 2.2.1 TiO2 Properties .......................................................................................................... 11 2.2.2 TiO2 Synthesis ........................................................................................................... 15 2.3 Photocatalytic Systems ..................................................................................................... 23 viii 2.3.1 Photocatalytic Mechanism ......................................................................................... 24 2.3.2 Particulate Systems .................................................................................................... 29 2.3.3 Photocatalytic Fuel Cells ........................................................................................... 31 2.3.4 Photocatalytic Fuel Cell Technologies for Waste water Treatment .......................... 35 2.4 TiO2 in Li-Ion Batteries ..................................................................................................