On Molybdenum Sulfides and Other Active Materials for Sustainable Energy Systems

On Molybdenum Sulfides and Other Active Materials for Sustainable Energy Systems A thesis with publication submitted to fulfil requirements for the degree of Doctor of Philosophy Jyah Strachan Laboratory of Advanced Catalysis for Sustainability Faculty of Science The University of Sydney 2020 Preface Preface Abstract To respond to the approaching climate crisis, the current energy landscape must shift towards sustainable, decarbonised systems. This shift will require the development of inexpensive and active energy conversion materials. The work within this thesis reports the investigation of several candidate materials, i.e. molybdenum sulfides and carbides, for use as catalysts and electrodes in energy conversion processes. These materials were chosen for their natural abundance, controllable morphologies, and varied chemistries. Chapter 1 focuses on the scope and potential of Chevrel phases (MxMo6S8) as catalytic materials. It includes a critical literature review that emphasises the unique features of Chevrel Phase catalysts and summarises the published catalytic reports. This survey highlights the underutilisation of Chevrel Phases as catalysts, laying the foundation for further investigations into the synthesis and tuning of highly active Chevrel Phase morphologies. These studies yielded nanoparticulate catalysts that exhibited excellent performance for the hydrogen evolution reaction (a current of 10mAcm-2 at 0.23 V and a Tafel slope of 68 mVdec-1). Chapter 2 focuses on the various morphologies of MoS2 and incorporates two reviews submitted for publication: the first review summarises all known reports of 3R-MoS2. The contradictory findings and nomenclature inconsistencies within the literature are clarified. The second review rectifies the errors in the literature on hydrothermally produced 1T-MoS2 and provides best practice analysis instructions for researchers to prevent future mistakes. The final section of Chapter 2 introduces new results of an investigation into the effect of crystal disorder on the electrochemical performance of MoS2 in hybrid batteries in order to aid the optimisation of MoS2 electrodes. Chapter 3 is comprised of a study that elucidates the structure of a highly active lignin valorisation catalyst, Mo2CxNx-1/TiN. A wide range of characterisation techniques was employed, including X-ray absorption spectroscopy, alongside microscopic and diffraction-based techniques, to show that the titanium nitride and molybdenum carbide phases are intimately mixed and that the catalyst incorporates terminal Mo≡N motifs. Chapter 4 includes two published studies on the silver catalysed reduction of 4-nitrophenol; a ubiquitous model reaction. The first involves a detailed kinetic analysis of the reaction mechanism to elucidate the role of oxygen during the induction period of the reaction. The research-level chemistry and protocols were then adapted to be used as a pedagogical tool to teach nanoscience and kinetics to undergraduate students. i Preface Statement of Originality The content of this thesis is my own work. This thesis has not been submitted for any degree or other purposes. I certify that the intellectual content of this thesis is the product of my own work and that all the assistance received in preparing this thesis and relevant sources have been acknowledged. In addition to the statements above, in cases where I am not the corresponding author of a published item, permission to include the published material has been granted by the corresponding author. Jyah Strachan, 20th December 2020 The work and results presented in this thesis are primarily my own, with the input of collaborators as below. Additionally, this thesis contains work which has been accepted or submitted for publication as follows: Chapter 1: All the work within this chapter was designed, conducted, and written by me with supervision from Anthony F Masters (AFM) and Thomas Maschmeyer (TM). Section 1.1 (The Catalytic Nature of Chevrel Phases in Review) has been published in the Materials Research Bulletin. Section 1.2 (Chevrel Phase Nanoparticles as Electrocatalysts for Hydrogen Evolution) has been published in ACS Applied Energy Materials. Chapter 2: All the work within this chapter was designed, conducted, and written by me with supervision from AFM and TM. Section 2.1 (3R-MoS2 in Review: History, Status, and Outlook) has been accepted for publication in ACS Applied Energy Materials. Section 2.2 (Critical Review: Hydrothermal Synthesis of 1T-MoS2 – an Important Route to a Promising Material) has been published in the Journal of Materials Chemistry A. These two sections (2.1 and 2.2) contain reproduced figures, used with permission, from articles as referenced. Section 2.3 (Influence of Crystal Disorder in MoS2 Cathodes for Secondary Hybrid Mg-Li Batteries) was designed, conducted, and written by Lu Chen and me with supervision from AFM and TM. Chapter 2.3 is in the final stages of preparation for submission to the Australian Journal of Chemistry. Chapter 3: This work was the continuation of a study by Alexander Yuen (AY) and co-workers. The EXAFS experiment was designed by all authors, conducted by Stuart A. Bartlett (SAB), AY, Bernt Johannessen, and me, and the data analysed by SAB. With the exception of the microscopy (for which Hongwei Liu aided in sample analysis), the remaining experiments were collaboratively designed by SAB, AY, and me, then conducted by me. The resulting manuscript was drafted by all authors. This work has been submitted to Physical Chemistry Chemical Physics and is currently under peer review. Chapter 4: The work in this chapter was designed, conducted, and written by Christopher D Barnett and me with supervision and input from AFM and TM. Section 4.1 has been published in ACS Catalysis. ii Preface Section 4.2 was designed, conducted, and written by Christopher D Barnett, Alice Motion and me, with supervision and input from AY, AFM, and TM. It has been published in the Journal of Chemical Education. Appendix: The appendix contains supplementary information to the chapters above. As supervisor for the candidature upon which this thesis is based, I can confirm that the authorship attribution statements above are correct. Professor Anthony Masters, 1st January 2021 Professor Thomas Maschmeyer, 20th December 2020 iii Preface Acknowledgements Tony and Thomas, thank you for the mountain of support that you have provided to guide me through the wild journey that the last few years have been. Thanks for smiling while I described the latest equipment malfunction or failed experiment. The hour at which you responded to my anxious emails never ceased to amaze me. You are both fantastic role models and I consider my time with you both to have been invaluable. Alex and Chris, thanks for dealing with my nonsense day in, day out. You’re both brilliant, and great friends. Thanks for fielding my infinite questions and putting in time to make sure this thesis looked as good as possible. To the lab members (Alfonso, Ellen, Eddie, the Lisas, Grace, Jake, Kevin, Sid, Gelion and others), thank you for the support, encouragement, and mischief. This PhD wouldn’t have been nearly as fun without you. To the GOST lab (Alvise, Maurizio, Manu, Ale, Robe, Carlotta and others) and Casa Primus (Alvise, Alix, Amanda), thank you for welcoming me into your families with open arms. SURMC, thank you for putting your faith in me and for being such a supportive community of misfits. Special mention to Sean, Tess, Matt, Mimes, Alex, and Jose for the friendship and adventures, and to Dec and Jess for your love and aggressive hospitality. To my friends at home: Jono, Jess, Alex and crew, thank you for letting me disappear for months on end and welcoming me back every time. I always appreciate your patience and love. To Rhiannon, thank you for your unwavering support through such a turbulent time in your life. I appreciate all that you gave and continue to give. This adventure truly couldn’t have been possible without you. To all the Griens, thank you for bringing me into your family – I put in the time; I know you’ll be proud! Finally, thank you to Mum, Dad, Indi, Shay, Eva, and all the Suttons and Strachans. Without two and a half decades of your support, I never would have achieved anything close to this. Thank you for always believing in me and facilitating this endless education of mine. I probably might stop collecting degrees now. I love you all. I acknowledge the Gadi of the Eora Nation, the traditional custodians of the land upon which this work took place. I pay respect to those who have cared and continue to care for Country. iv Preface Table of Contents Preface ................................................................................................................................................................................... i Introduction ......................................................................................................................................................................... 1 Chapter 1.1 ........................................................................................................................................................................... 4 The Catalytic Nature of Chevrel Phases in Review Chapter 1.2 ......................................................................................................................................................................... 18 Chevrel Phase Nanoparticles as Electrocatalysts for Hydrogen Evolution Chapter 2.1 ........................................................................................................................................................................

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