«Eranda Nikolla A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Chemical Engineering) in ...»
COMBINED EXPERIMENTAL/THEORETICAL APPROACH
TOWARD THE DEVELOPMENT OF CARBON TOLERANT
ELECTROCATALYSTS FOR SOLID OXIDE FUEL CELL ANODES
A dissertation submitted in partial fulfillment
of the requirements for the degree of
Doctor of Philosophy
in The University of Michigan
Assistant Professor Suljo Linic, Co-chair Professor Johannes W. Schwank, Co-chair Professor Erdogan Gulari Professor John W. Halloran Professor Phillip E. Savage © Eranda Nikolla “The most important thing in science is not so much to obtain new fact as to discover new ways of thinking about them” Sir William Bragg (1862-1942) “The important thing is not to stop questioning” Albert Einstein (1879-1955) This dissertation is dedicated to my parents Liljana and Nik Nikolla for all their love and endless support.
I would like to thank my thesis committee: Prof. Phillip Savage, Prof. John Halloran and Prof. Erdogan Gulari. I am very thankful to Prof. Savage for all his support and willingness to listen and share his advice with me in multiple occasions. I would like to thank Prof. Halloran for his help with synthesizing the solid oxide fuel cells. I really appreciate his readiness to help me all the time. I would also like to thank Prof. Gulari for being very supportive of my work.
I believe that the Department of Chemical Engineering at the University of Michigan has a number of great individuals as part of their departmental staff. I would like to thank Leslie Cypert and Sandy Swisher for all their help and consistent support.
Furthermore, I would also like to acknowledge Claire O’Conner, Linda Casto, Susan Hamlin, Shelly Fellers, Ruby Sowards, Christine Moellering and Tina Jimenez for their
reactors and boats. I really appreciate his willingness to help every time I knocked on his door.
I also believe that I have had the great opportunity to work with bright individuals in both the Linic and Schwank research groups. I really appreciate their support and assistance. These individuals are: Linic research group: Siris Laursen, Hongliang Xin, Neil Schweitzer, David Ingram, Phillip Christopher, Adam Holewinski, Matthew Morabito, Katrina Ramsdell and Schwank research group: Tom Gilbert, Jim Bucher, Joe Mayne, Ben Harris, Liz Ranney, Tom Westerich, Sameer Parvathikar, Steve Edmund, Xiaoyin Chen, Hui Feng. I would like to wish them all the best during the rest of their graduate studies and in their future careers.
I have also been very fortunate to have had the opportunity to work with a number of great undergraduate students. I would like to thank Adam Holewinski (now a graduate student in Prof. Linic’s group) for performing some of the initial density functional theory work. I would like to thank Teresa Mitisi for being very helpful with synthesizing supported catalyst and solid oxide fuel cells. I would like to thank Matt Morobito (now a graduate student in Prof. Linic’s group) for all his help with synthesizing and testing solid oxide fuel cells. I would also like to thank Preeta Maitra for help with synthesizing solid oxide fuel cells.
At University of Michigan I have also met a number of individuals that have greatly impacted my graduate work. I would like to thank Dr. Kai Sun for his tremendous help with electron microscopy and spectroscopy. I really appreciate his endless patience in helping me with operating the scanning electron microscope and the electron energy
qualifying and preliminary examinations. I really appreciate his support especially during my first two years of graduate school. I would like to thank Dr. Joydeep Mukherjee for his help when he was a postdoctoral fellow in Prof. Linic’s group. I really appreciate his help with density functional theory calculations.
I would like to express my deepest gratitude my best friend, Maha Hammoud, for all her support and help throughout my stay at the University of Michigan. She has been more than a friend; she has been like a sister that has always advised and supported me.
She has been part of my family in Ann Arbor. I would also like to thank her husband, Ali, for all his support and her daughter Alma for being so loving. I would also like to congratulate her on the new addition to her family, her baby girl Rina.
I would also like to thank Dr. Valarie Thomas for being a great friend. It has been a great pleasure getting to know her and I really appreciate all her support. I also would like to thank Natalie Rebacz for being a great friend and always supporting me. It has been great getting to know her and I wish her all the best in her future endeavors. I would also like to acknowledge Peter Aurora, Hima Nandivada, Saadet Albayrak, Bilge Ozel, Desh Mukhija, Khamir Mehta and Tony Lachawiec for being great friends.
I would not be in graduate school if it were not for the advice and consistent support of my undergraduate advisor Prof. Kenneth Harmon. He was instrumental in convincing me to pursue my graduate studies. I cannot thank him enough for giving me the opportunity to work in his lab. I am in debt to him for his guidance and support throughout my undergraduate studies.
consistent support during my graduate studies. I cannot thank them enough for their help and encouragement every step of the way.
Last but not least, I would like to thank my family for their endless love and consistent support. I would like to thank my brother for always encouraging me and being supportive of my decisions. I would also like to thank his wife Magdalena for her support and my niece Fiona for being so joyous and loving all the time. I would like to express my sincere thanks to my parents Liljana and Nik Nikolla. They are the best parents in the world and I don’t think that there exist enough words to express my gratitude to them for sacrificing a lot so my brother and I can succeed in life. I am proud to be their daughter, to have known and learned from them.
DEDICATION…………………………………………………………………………...ii ACKNOWLEDGEMENTS…………………………………………………………….iii LIST OF FIGURES………………………………………………………………….....xii LIST OF TABLES…………………………………………………………………......xix ABSTRACT……………………………………………………………………………..xx CHAPTER
1. GENERAL INTRODUCTION
1.2 RATIONAL CATALYST DESIGN
1.3 FUEL CELL TECHNOLOGY
1.4 SOLID OXIDE FUEL CELLS
1.5 CARBON POISONING
1.6 SCOPE OF THE THESIS
2. EXPERIMENTAL AND THEORETICAL TECHNIQUES
2.3 SYNTHESIS TECHNIQUES
2.3.1 Catalyst Preparation
2.3.2 Solid Oxide Button Cell Preparation
2.4 MICROSCOPIC AND SPECTROSCOPIC TECHNIQUES
2.4.1 X-Ray Diffraction (XRD)
2.4.2 Scanning electron microscopy (SEM)
2.4.3 X-ray Photoelectron Spectroscopy (XPS)
vii 2.4.4 Auger Electron Spectroscopy (AES)
2.4.5 Scanning Transmission Electron Microscopy (STEM) and Transmission Electron Microscopy (TEM)
2.4.6 Energy Dispersive X-ray Spectroscopy (EDS)
2.4.7 Electron energy loss spectroscopy (EELS)
2.4.8 Reactor Studies
2.4.9 Temperature Programmed Reduction (TPR)
2.4.10 Thermal gravimetric analysis (TGA)
2.4.11 SOFC electrochemical testing and Impedance Spectroscopy
2.5 THEORETICAL TECHNIQUES
2.5.1 Density Functional Theory (DFT)
3. CONTROLLING CARBON CHEMISTRY ON NI BY SURFACEALLOYING….
3.3 THEORETICAL DETAILS
3.4 EXPERIMENTAL DETAILS
3.4.2 BET Surface Area Measurements
3.4.3 Temperature Programmed Reduction (TPR).
3.4.4 X-Ray Diffraction (XRD).
3.4.5 X-ray Photoelectron Spectroscopy (XPS)
3.4.6 Scanning Transmission Electron Microscopy (STEM), Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray Spectroscopy (EDS)...................61 3.4.7 Reactor Testing
3.5 RESULTS AND DISCUSSIONS
3.5.1 DFT Studies
3.5.2 Catalysts synthesis and characterization
3.5.3 Reactor Studies
4. HYDROCARBON STEAM REFORMING ON NI ALLOYS AT SOLID OXIDEFUEL CELL OPERATING CONDITIONS
4.3 EXPERIMENTAL SECTION
4.3.1 Catalyst Synthesis
4.3.2 Reactor Studies
4.3.3 Temperature Programmed Reduction (TPR)
4.3.4 Scanning Transmission Electron Microscopy (STEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Spectroscopy (EDS) and Electron Energy Loss Spectroscopy (EELS).
4.3.5 Density Functional Theory (DFT)
5. NI ALLOYS AS PROMISING CARBON TOLERANT SOFC ANODES........107
5.2.1 Experimental methods
5.2.2 Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS)
6. METHANE STEAM REFORMING KINETICS ON SN/NI SURFACEALLOY………
6.3 EXPERIMENTAL METHODS
6.4 RESULTS AND DISCUSSIONS
6.4.1 Kinetic Studies
6.4.2 Isotope Labeling Studies
6.4.3 DFT Calculations
7. MEASURING AND RELATING THE ELECTRONIC STRUCTURE OF
NONMODEL SUPPORTED CATALYTIC MATERIALS TO THEIRPERFORMANCE
7.3 EXPERIMENTAL SECTION AND METHODOLOGY
7.3.1 Catalyst Synthesis
7.3.2 Electron energy loss spectroscopy (EELS) in scanning transmission electron microscope (STEM)
7.3.3 X-ray photoelectron spectroscopy (XPS)
7.3.4 Reactor Studies
7.3.5 Density functional theory (DFT) calculations
7.4 RESULTS AND DISCUSSIONS
8. NI SURFACE ALLOYS AS CARBON TOLERANTELECTROCATALYSTS…..
8.3 EXPERIMENTAL SECTION
8.3.1 Density Functional Theory (DFT)
8.3.2 Catalyst Synthesis
x 8.3.3 Reactor Studies
8.3.4 Thermal gravimetric analysis (TGA)
8.4 RESULTS AND DISCUSSIONS
8.4.1 Formation of Surface Alloys
9. GENERAL CONCLUSIONS AND FUTURE WORK
9.2 GENERAL CONCLUSIONS
9.3 FUTURE RESEARCH DIRECTIONS
1.1. A schematic of an anode, electrolyte, cathode assembly of a SOFC. The image on the right is the schematic of the triple phase boundary (TPB) region............6
1.2. a) A fresh Ni/YSZ SOFC anode pellet b) The Ni/YSZ anode pellet after exposed to isooctane steam reforming c and d) transmission electron microscope (TEM) images of the carbon deposits of the catalysts covered by carbon deposits
2.1 A schematic of the materials and fuel cells synthesized in this thesis..............22
2.2. The upper graph shows the XRD spectrum obtained for a powder Ni/YSZ catalyst. The middle line graph shows the standard YSZ spectrum obtained from Jade. The bottom line graph shows the standard spectrum for Ni obtained from Jade.
2.3. Schematic of the process that occurs in a x-ray photoelectron spectroscopy experiment
2.4. Schematic of Auger effect that occurs in the Auger Electron Spectroscopy (AES) experiment.
2.5. Schematic of the basic components in TEM and STEM .
2.6. Schematic of process that occurs in energy dispersive x-ray spectroscopy (EDS)
2.7. Schematic of process that occurs in electron energy loss spectroscopy (EELS)
2.8. Schematic of reactor set-up utilized to run the steady state reactor experiments.
2.9. Schematic of solid oxide button cell test assembly
2.10. I-V and power curves generated for a SOFC at 750°C under 50 sccm of H2...43
2.12. Nyquist plot obtained for a Ni/YSZ|YSZ|LSM/YSZ SOFC at open circuit voltage (OCV), 1013 K while operating under a stream of 50 sccm of humidified H2
2.13. Images of a) Ni (111) slabs separated by the vacuum space. b) Ni (111) unit cell utilized to represent the Ni terrace sites (well-coordinated) and c) Ni (211) unit cell utilized to represent the Ni step/edge sites (under-coordinated).........48