Bifunctional Oxygen Reduction/Evolution Catalysts for Rechargeable Metal-Air Batteries and Regenerative Alkaline Fuel Cells by Pooya Hosseini-Benhangi M.Sc., Ferdowsi University of Mashhad, 2011 B.Sc., Ferdowsi University of Mashhad, 2009 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES (Chemical and Biological Engineering) THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) December 2016 © Pooya Hosseini-Benhangi, 2016 Abstract The electrocatalysis of oxygen reduction and evolution reactions (ORR and OER, respectively) on the same catalyst surface is among the long-standing challenges in electrochemistry with paramount significance for a variety of electrochemical systems including regenerative fuel cells and rechargeable metal-air batteries. Non-precious group metals (non- PGMs) and their oxides, such as manganese oxides, are the alternative cost-effective solutions for the next generation of high-performance bifunctional oxygen catalyst materials. Here, initial stage electrocatalytic activity and long-term durability of four non-PGM oxides and their combinations, i.e. MnO2, perovskites (LaCoO3 and LaNiO3) and fluorite-type oxide (Nd3IrO7), were investigated for ORR and OER in alkaline media. The combination of structurally diverse oxides revealed synergistic catalytic effect by improved bifunctional activity compared to the individual oxide components. Next, the novel role of alkali-metal ion insertion and the mechanism involved for performance promotion of oxide catalysts were investigated. Potassium insertion in the oxide structures enhanced both ORR and OER performances, e.g. 110 and 75 mV decrease in the OER (5 mAcm-2) -2 and ORR (-2 mAcm ) overpotentials (in absolute values) of MnO2-LaCoO3, respectively, during galvanostatic polarization tests. In addition, the stability of K+ activated catalysts was improved compared to unactivated samples. Further, a factorial design study has been performed to find an active nanostructured manganese oxide for both ORR and OER, synthesized via a surfactant-assisted anodic electrodeposition method. Two-hour-long galvanostatic polarization at 5 mAcm-2 showed the -1 lowest OER degradation rate of 5 mVh for the electrodeposited MnOx with 270 mV lower OER overpotential compared to the commercial γ-MnO2 electrode. ii Lastly, the effect of carbon addition to the catalyst layer, e.g. Vulcan XC-72, carbon nanotubes and graphene-based materials, was examined on the ORR/OER bifunctional activity and durability -1 of MnO2-LaCoO3. The highest ORR and OER mass activities of -6.7 and 15.5 Ag at 850 and 1650 mVRHE, respectively, were achieved for MnO2-LaCoO3-multi_walled_carbon_nanotube- graphene, outperforming a commercial Pt electrode. The factors affecting the durability of mixed- oxide catalysts were discussed, mainly attributing the performance degradation to Mn valence changes during ORR/OER. A wide range of surface analyses were employed to support the presented electrochemical results as well as the proposed mechanisms. iii Preface The materials presented in the following dissertation are confidential and subject to United States and Canadian patent applications. The research work presented in this thesis including literature review, research proposal, experimental work, data interpretation, proposed hypothesis and preparation of this dissertation, four research manuscripts, five conference presentations along with one provisional and one U.S./Canadian patent applications are completed by Pooya Hosseini-Benhangi under the direct supervision of Professors Előd Gyenge and Akram Alfantazi at the Department of Chemical & Biological Engineering Department, the University of British Columbia. The following publications, manuscripts, presentations and patent applications are developed form the work presented in this dissertation: A version of chapter 3 and 4 was published and presented in: 1) P. Hosseini-Benhangi, A. Alfantazi, E. Gyenge, “Manganese dioxide-based bifunctional oxygen reduction/evolution electrocatalysts: Effect of perovskite doping and potassium ion insertion”, Journal of Electrochimica Acta, 123 (2014) 42-50. 2) P. Hosseini-Benhangi, M. A. Garcia-Contreras, A. Alfantazi, E. Gyenge, “Method for enhancing the bifunctional activity and durability of oxygen electrodes with mixed oxide electrocatalysts: Potential driven intercalation of potassium”, Journal of The Electrochemical Society, 162 (2015) F1356-F1366. 3) P. Hosseini-Benhangi, A. Alfantazi, E. Gyenge, “Investigation of non-precious metal bifunctional oxygen cathodes for alkaline fuel cells and batteries”, Hydrogen Fuel Cell conference (HFC 2013), Vancouver, Canada, June 2013. iv 4) P. Hosseini-Benhangi, A. Alfantazi, E. Gyenge, “Doped MnO2-based oxygen reduction and evolution catalysts for bifunctional cathodes in alkaline electrochemical power sources”, 224th Electrochemical Society Meeting, San Francisco, U.S., October 2013. 5) P. Hosseini-Benhangi, A. Alfantazi, E. Gyenge, “MnO2-based bifunctional oxygen catalyst for rechargeable metal/air batteries: The effect of K+ intercalation”, 226th Electrochemical Society Meeting, Cancun, Mexico, October 2014 & AIChE 2014 Annual Meeting, Atlanta, U.S., November 2014. A version of chapter 5 is in preparation for publication and was presented at a conference: 6) P. Hosseini-Benhangi, A. Alfantazi, E. Gyenge, “Surfactant-assisted electrodeposition of Mn oxides as promising ORR/OER bifunctional non-PGM electrocatalysts: Factorial design study of the electrodeposition factors”, to be submitted. 7) E. Gyenge, P. Hosseini-Benhangi, C. H. Kung, A. Alfantazi, “Toward active and durable oxygen reduction/oxygen evolution (ORR/OER) bifunctional non-PGM electrocatalysts for rechargeable metal-air batteries and regenerative fuel cells”, International Workshop on Advanced Materials and Nanotechnology (IWAMN 2016), Hanoi, Vietnam, November 2016. A version of chapter 6 is in preparation for publication and was presented at a conference: 8) P. Hosseini-Benhangi, M. A. Garcia-Contreras, A. Alfantazi, E. Gyenge, “Carbon support effect on ORR/OER bifunctional activity and durability of non-PGM mixed- oxide catalyst: Graphene vs. commercial carbon materials”, to be submitted. v 9) M. Garcia, P. Hosseini-Benhangi, A. Taheri, E. Gyenge, “The effect of graphene as a support for non-PGM bifunctional oxygen catalyst in rechargeable metal/air batteries”, AIChE 2014 Annual Meeting, Atlanta, U.S., November 2014. For the items 1 to 9, all of the experiments were performed by Pooya Hosseini-Benhangi and the manuscripts were co-authored by Előd Gyenge with the support from Akram Alfantazi. For items 2, 8 and 9, the experiments were performed by Pooya Hosseini-Benhangi with laboratory recommendations from Dr. Miguel Angel Garcia-Contreras. The manuscripts and presentations mentioned in items 2, 8 and 9 were also co-authored by Dr. Miguel Angel Garcia-Contreras. Parts of chapters 2, 3, 4, 5 and 6 from this dissertation were filed as United States and Canadian patent applications: 10) E. Gyenge, P. Hosseini-Benhangi, “An oxygen electrode and a method of manufacturing the same”, U.S. (15/251,267) and Canadian (2,940,921) patent applications, filed on August 30th, 2016. where all of the experiments for this intellectual property were performed by Pooya Hosseini-Benhangi. The U.S. and Canadian patent applications were co-authored by Előd Gyenge and Brian Yat-Ming Lee (Patent Attorney). vi Table of Contents Abstract .......................................................................................................................................... ii Preface ........................................................................................................................................... iv Table of Contents ........................................................................................................................ vii List of Tables ............................................................................................................................... xii List of Figures ............................................................................................................................. xiv Nomenclature .......................................................................................................................... xxxii List of Abbreviations ...............................................................................................................xxxv Acknowledgements .............................................................................................................. xxxviii Dedication ................................................................................................................................... xlii Chapter 1: Introduction ................................................................................................................1 1.1 Summary ..................................................................................................................... 1 1.2 Bifunctional catalysts for ORR and OER in alkaline batteries and fuel cells ............ 9 1.2.1 Nobel metals and their alloys ............................................................................ 10 1.2.2 Manganese dioxide ........................................................................................... 11 1.2.2.1 Electro-reduction of MnO2 .......................................................................... 15 1.2.2.2 Oxygen reduction reaction on