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Seminar: Roles of Oxygen Lattice Defects on the Oxygen Reduction Reaction Kinetics in Solid Oxide Fuel Cell Cathodes
September 14, 2017 @ 4:00 pm - 5:00 pm
Xingbo Liu, Ph.D.
Mechanical & Aerospace Engineering Department Benjamin M. Statler College of Engineering & Mineral Resources West Virginia University
September 14, 2017
C112 OHR (Oliver H. Raymond Civil Engineering Building)
Roles of Oxygen Lattice Defects on the Oxygen Reduction Reaction Kinetics in Solid Oxide Fuel Cell Cathodes
For perovskites, we developed a multi-domain 1-D physical model incorporating multi-step charge transfer to examine the competitive behaviors between the paralleled 3PB and 2PB kinetic pathways. Analyses identified the limitation of surface oxygen ion diffusion as the mechanism for 3PB-to-2PB transition. The model also proved that surface reactions are driven predominantly by electrochemical forces at the 3PB, while being controlled by oxygen vacancy concentration variation at regions away from 3PB. For Ruddlesden–Popper (R-P) phases, the governing factors of the ORR are identified as oxygen adsorption and incorporation. The incorporation rate is drastically dependent on the amount of interstitial oxygen. Since the unfilled interstitial sites serve to accommodate the adsorbed oxygen during incorporation, more oxygen interstitials would seem to suppress the kinetics of this process. We proposed a physical model to reconcile the discrepancy between the experimental results and intuitive reasoning. This model illustrates a possibility of how oxygen interstitials works to regulate the exchange rate, and how the contradiction between oxygen vacancies and oxygen interstitials is harmonized so that the latter in the R–P structure also positively promotes the incorporation rate in the ORR.
Refreshments will be served!
Dr. Xingbo Liu received his Ph.D. in Materials Science from University of Science and Technology Beijing in 1999, and is currently a professor and associate chair for research in the Mechanical & Aerospace Engineering Department at West Virginia University. Dr. Liu has developed a national recognized research program on materials for the next generation energy conversion and storage, with a focus on solid oxide fuel cells and batteries. He has been serving in leading roles in TMS, ACerS, and ECS. He has received numerous awards, including one R&D 100 Award (2011) for his development of SOFC interconnect coating, TMS Early Career Faculty Fellow Award (2010), State of West Virginia Innovator of the Year (2013), WVU CEMR Researcher of the Year (2015, 2011), and Outstanding Researcher Awards (2015, 2011, 2009, 2008). He was also elected as a Fellow of ASM International (2015), and received TMS Brimacombe Medal (2016).