A THEORETICAL AND EXPERIMENTAL INVESTIGATION OF PROTON TRANSPORT BETWEEN THE ELECTROLYTE IN A REVERSIBLE FUEL CELL AND A CARBON- BASED HYDROGEN STORAGE A thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy By Shahin Heidari College of Science, Engineering and Health RMIT University Melbourne, Victoria, Australia March 2017 1 DECLARATION I, Shahin Heidari, hereby submit the thesis entitled “a theoretical and experimental investigation of proton transport between the electrolyte in a reversible fuel cell and a carbon- based hydrogen storage” for the degree of Doctor of Philosophy, and certify that except where due acknowledgement has been made, the work is that of the author alone; the work has not been submitted previously, in whole or in part, to qualify for any other academic award, and that the content of the thesis is the result of work that has been carried out since the official commencement date of the approved research program. Shahin Heidari March 2017 2 ACKNOWLEDGMENTS I would like to acknowledge my senior supervisor, Professor John Andrews, for sharing his ideas and knowledge and supporting me in every step of my PhD journey. I would like to thank Professor Aliakbar Akbarzadeh and Doctor Abhijit date for giving me the opportunity of teaching and tutoring. I would like to thank all my friends and colleagues at RMIT University SAMME School and specifically Energy CARE group for their support. Many thanks also go to our hydrogen group at RMIT, specifically Dr. Amandeep Oberoi and Mr. Saeed Seif Mohammadi for sharing with me their knowledge in this field of study. I would like to thank my family and friends in Melbourne for supporting me during my study. I dedicate this thesis to my parent Behrouz Heydari and Akram homafar, for their never- ending love, support, and encouragement. 3 Contents EXECUTIVE SUMMARY .................................................................................................................. 15 1. INTRODUCTION ........................................................................................................................ 20 1.1 Background .............................................................................................................................. 20 1.2 Aim and, objectives ................................................................................................................. 21 1.3 Research questions ................................................................................................................... 22 1.4 Scope ........................................................................................................................................ 23 1.5 Planned outcomes .................................................................................................................... 24 1.6 Guide to thesis ......................................................................................................................... 25 2. METHOD ..................................................................................................................................... 26 2.1 Overall methodological approach ............................................................................................ 26 2.2 Theoretical investigations ........................................................................................................ 26 2.3 Experimental procedures ......................................................................................................... 27 2.3.1 Carbon-base materials as the hydrogen storage medium ................................................ 27 2.3.2 Fabrication of solid-state electrode ................................................................................. 27 2.3.3 Double layer capacitance measurement .......................................................................... 28 2.3.4 Hydrogen storage capacity measurement ........................................................................ 28 2.3.5 Testing the best performing electrode in proton battery ................................................. 28 2.3.6 Activities ......................................................................................................................... 28 3 ELECTROCHEMICAL STORAGE OF HYDROGEN IN CARBONS: A STATE OF THE ART REVIEW ............................................................................................................................................... 30 3.1 Concept of reversible hydrogen fuel cell ................................................................................. 30 3.2 Proton battery ........................................................................................................................... 36 3.2.1 The concept of the proton battery ................................................................................... 36 3.2.2 Limitations of MH storage electrode .............................................................................. 40 3.3 Electrochemical hydrogen storage in carbon-based materials ................................................. 40 3.3.1 Potential advantages of carbon electrodes in a proton battery ........................................ 40 3.3.2 Activated carbons ............................................................................................................ 41 3.3.3 Storage of gaseous hydrogen in activated carbons .......................................................... 44 3.3.4 Previous work electrochemical storage of hydrogen in activated carbons ...................... 45 3.3.5 Proton conduction within electrodes for electrochemical hydrogen storage in activated carbons 50 3.4 Gaps in knowledge and understanding .................................................................................... 57 4 4 A THEORETICAL ANALYSIS OF AN ELECTROCHEMICAL CELL WITH AN INTEGRATED HYDROGEN STORAGE ELECTRODE .................................................................. 58 4.1 Overview .................................................................................................................................. 58 4.2 A general model of a reversible electrochemical cell with a porous hydrogen storage electrode 59 4.2.1 The basic electrochemical cell considered ...................................................................... 59 4.2.2 Charging (electrolyser) mode (E-mode) ......................................................................... 59 4.2.3 Fuel cell mode ................................................................................................................. 65 4.3 Conclusion ............................................................................................................................... 67 5 MATLAB SIMULATION OF AN ELECTROCHEMICAL HYDROGEN STORAGE CELL: BASE CASE AND PARAMETRIC STUDY ...................................................................................... 68 5.1 Overview .................................................................................................................................. 68 5.2 Cell characteristic..................................................................................................................... 68 5.3 Base case analysis .................................................................................................................... 70 5.4 Parametric analysis: effect of varying key input parameters ................................................... 77 5.4.1 Changing charge transfer coefficients ............................................................................. 78 5.4.2 Exchange current density ................................................................................................ 81 5.4.3 Reversible potentials ....................................................................................................... 86 5.5 Conclusion ............................................................................................................................... 87 6 AN EXPERIMENTAL STUDY OF ELECTROCHEMICAL HYDROGEN STORAGE IN SELECTED CARBON-BASED MATERIALS ................................................................................... 89 6.1 Introduction .............................................................................................................................. 89 6.2 Carbon samples and their physical properties .......................................................................... 90 6.2.1 Selection of carbon materials .......................................................................................... 90 6.2.2 Activated carbon samples................................................................................................ 90 6.2.3 Graphene platelets ........................................................................................................... 93 6.2.4 Spherical conductive graphite ......................................................................................... 94 6.3 Fabrication of carbon-PTFE electrodes ................................................................................... 95 6.3.1 Weighing and mixing ...................................................................................................... 95 6.3.2 Moulding ......................................................................................................................... 97 6.4 Proton and electron conductivity measurements ..................................................................... 98 6.4.1 The