Effects of Palladium Thin Films on the Hydrogen Permeability of Pd-Cu Alloy Membranes by Naser Azzat Al-Mufachi A thesis submitted to The University of Birmingham for the degree of DOCTOR OF PHILOSOPHY WITH INTEGRATED STUDIES IN HYDROGEN, FUEL CELLS AND THEIR APPLICATIONS School of Chemical Engineering College of Engineering and Physical Sciences University of Birmingham April 2015 University of Birmingham Research Archive e-theses repository This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder. Surat Al-Fatihah In the name of God, the infinitely Compassionate and Merciful. Praise be to God, Lord of all the worlds. The Compassionate, the Merciful. Ruler on the Day of Reckoning. You alone do we worship, and You alone do we ask for help. Guide us on the straight path, the path of those who have received your grace; not the path of those who have brought down wrath, nor of those who wander astray. Amen. ~ i ~ It was a dark and lonely road, Longest journey ahead, Over again mistakes were made, Verily my heart was in dismay, Encouragement came in the form of an angel, Enlightenment, Made of magnificence, Made me want again, Away went my plight. ~ ii ~ Abstract The hydrogen permeability of surface modified Pd 60 Cu 40 wt% (Pd 47.3 Cu 52.7 at%) membranes have been determined for the first time. Surface modification was accomplished through the deposition of Pd thin films of three different thicknesses (95.5 ± 0.1, 797.4 ± 0.2 and 1,409.6 ± 0.2 nm) on to one side of a range of as-received Pd 60 Cu 40 wt% membranes via magnetron sputtering. The Pd 60 Cu 40 wt% membrane coated with a 1,409.6 ± 0.2 nm thick Pd thin film positioned on the feed side (445 kPa of hydrogen pressure) and cycled between 50 and 450 °C achieved the highest hydrogen permeability of 1.09 × 10 -8 mol m-1 s-1 Pa -0.5 at 450 °C during the third cycle. This is a 58% increase on the value measured for the as-received Pd 60 Cu 40 wt% under the same conditions. This improvement can be attributed to a Pd-rich Pd-Cu face centred cubic (FCC) phase forming through interdiffusion between the Pd thin film and bulk Pd-Cu membrane as a result of the test conditions used during hydrogen permeability measurements. This introduces a larger hydrogen concentration gradient across the membrane due to the relatively high hydrogen solubility of the Pd-rich Pd-Cu FCC phase resulting in the observed increase in permeability. A hydrogen pressure of 445 kPa produced an increase in interdiffusion rate compared with 100 kPa of pressure. This is related to a higher hydrogen pressure introducing a larger number of vacancy-hydrogen clusters resulting in increased atomic mobility. The Pd 60 Cu 40 wt% membranes coated with a 797.4 ± 0.2 and 1,409.6 ± 0.2 nm thick Pd thin films retained an almost pure Pd surface throughout cycling between 50 and 450 °C with a feed and permeate hydrogen pressure of 445 and 100 kPa, respectively. For the deposition technique and test conditions used throughout this work, these surface modified membranes appear to stabilise the Pd thin films upon cycling across the critical temperature of 295 °C. ~ iii ~ Dedication Four years ago the civil war in my country began. I humbly dedicate my PhD to the fallen innocent men, women and children of Syria. I also dedicate my work to the innocent lives lost in Gaza and Palestine. It may seem that the world has forgotten you. I haven’t. I have further dedicated my PhD to the memory of my late co-supervisor Dr Waldemar Bujalski. A true inspiration. Gone but never forgotten. ا . ~ iv ~ Acknowledgements First and foremost, I would like to say thank you to Allah for giving me the chance to explore his creations. It has truly been an honour. I credit my big sister Jeehan Al-Mufachi for my passion of science. She was the first to introduce me to the periodic table, the first element was hydrogen. My uncle Mohammad Raficq Kurimbokus is the reason I am here, he talked me into it and to him I am grateful. I would like to thank and express my gratitude towards Dr John Speight, Prof. David Book and Dr Waldemar Bujalski for their guidance throughout the duration of my research. Special thanks to Prof. Robert Steinberger-Wilckens and Dr Neil Rees for coming on board last minute, their help and support will always be appreciated. Many thanks go to the Hydrogen Materials Group and the DTC students for their helpful support throughout the years. Thank you to NEXUS nanoLab for all of their help and support. Thanks to Dr Anwar Sattar, a great friend. Also thank you to Rayan Ameen and Dilveen Mohammed for their much needed help and friendship. Special thanks to Emma, a great woman. Her love and support helped to make this happen. I am also grateful for the financial support of the EPSRC and the DTC. In addition, special thanks to Johnson Matthey Noble Metals for supply of the Pd-Cu foil used in this work ~ v ~ Modules and mini-projects I began the doctoral training centre (DTC) in Hydrogen, Fuel Cells and their Applications on November 10 th 2010. In addition to the PhD element of this course, it was a requirement to achieve 120 module credits and to complete a series of mini-projects. Modules The following modules were successfully passed during the course of the DTC: • Marketing and TQM • Materials for Energy Generation and Storage • Materials for Hydrogen and Fuel Cell Technology • Presentation Skills • Coniston Team Building Skills • Project Management • Business Methods and Industrial Economics • Materials for Sustainable Environmental Technology • Measurement Techniques • Public Engagement • The Energy System • Consultancy Skills • Electrochemistry ~ vi ~ Mini-projects An industrial mini-project was carried out in collaboration with Johnson Matthey Noble Metals to identify the composition of a range of their Pt-Pd alloy samples using X-ray diffraction (XRD). This 18 month project began in March 2011 and concluded November 2012. A series of heat treatments were used to homogenise the alloy samples prior to characterisation. Using XRD, it was possible to determine the lattice parameter of the alloy samples and from this the composition was calculated. Composition of the alloy samples were also determined using density measurements in order to compare with the compositions obtained using XRD. At the end of the project, a report was compiled for Johnson Matthey presenting all of the findings. I delivered a talk at the Imperial College London monthly DTC meeting in the summer of 2011 as a part of an interdisciplinary mini-project. The talk briefly described my research to an audience of DTC students and also included a tour of the fuel cell labs. In June 2011, I and a team of students setup a stall at the Gloucester Motor Show where we displayed the hydrogen fuel cell microcabs to the general public and engaged in public awareness of hydrogen fuel cell technology. During January 2012, I and two other colleagues delivered an outreach talk on hydrogen, fuel cells and their applications at Ninestiles Secondary School to a class of GCSE and BTEC students. This involved a PowerPoint presentation with live demonstrations of a portable hydrogen fuel cell. ~ vii ~ Publications and events Publications • N. A. Al-Mufachi, N. V. Rees, and R. Steinberger-Wilkens. Hydrogen selective membranes: A review of palladium-based dense metal membranes. Renewable and Sustainable Energy Reviews 47 (2015): 540-551. A majority of the literature review chapter for this thesis has been derived from this article. • N.A. Al-Mufachi, S. Nayebossadri, J.D. Speight, W. Bujalski, R. Steinberger-Wilkens, D. Book. Effects of Pd thin films on the hydrogen permeability of Pd 60 Cu 40 wt% alloy membranes. Submitted to the Journal of Membrane Science. Events • Talk given at the 10 th ISCARW Hydrogen, Regulations Codes and Standards, 24-28 th January 2011 in Belfast, Northern Ireland. • Poster presented at the 7th International Hydrogen and Fuel Cell Conference, 30 th March 2011 in Birmingham, UK. • Poster presented at the International Hydrogen Research Showcase, 13-15 th April 2011 in Birmingham, UK. • Poster presented at the Research Poster Conference, 15 th June 2011 in Birmingham, UK. • Talk and poster presented at the 2 nd Annual Hydrogen DTC Conference, 28 th September 2011 in Birmingham, UK. ~ viii ~ • Talk and poster presented at the 3rd Zing Hydrogen & Fuel Cells Conference, 1-5th December 2011 in Xcaret, Mexico. Won the abstract competition prize which was an all expenses paid trip to attend the conference. • Poster presented at the 8th International Hydrogen and Fuel Cell Conference, 29 th March 2012 in Birmingham, UK. • Poster presented at the International Symposium on Metal-Hydrogen Systems, 21-26 th October 2012 in Kyoto, Japan. • Poster presented at the 9th International Hydrogen and Fuel Cell Conference, 20-21 st March 2013 in Birmingham, UK. th th • Talk given at the 4 European PEFC & H 2 Forum, 2-5 July 2013 in Lucerne, Switzerland. • Poster presented at the European Technical School on Hydrogen and Fuel Cells 23-27 th June 2014 in Crete, Greece.