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SUMMARY:Cancelled Event - IMX Seminar Series - The Remarkable Influence of
  Zr-doping on the Chemistry and Reactivity of Ceria
DTSTART:20200323T131500
DTEND:20200323T141500
DTSTAMP:20260513T034341Z
UID:6b841850c3644d56bc755baed94551c622871c8c34a69f0e86717f35
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Sossina Haile\, Northwestern\, USA\nZirconia substituted
  ceria is a widely studied material system with immense importance in hete
 rogeneous catalysis. Enhancements to a range of properties in the oxide ha
 ve been attributed to the presence of zirconium\, in particular\, oxygen s
 torage capacity\, oxygen mobility\, and surface reaction rate. All of thes
 e features have furthermore been connected with the observation of an incr
 ease in the concentration of reduced Ce3+ species in the presence of Zr4+.
  Using a suite of characterization tools we establish the precise role tha
 t zirconium plays in controlling these properties. Our bulk thermogravimet
 ric measurements reveal that in the presence of Zr the oxygen non-stoichio
 metry (d) of Ce1-xZrxO2-d is indeed enhanced. Using angle-resolved X-ray A
 bsorption Near Edge Spectroscopy (XANES)\, we quantify under technological
 ly relevant conditions the Ce3+ concentration in the surface (2-3 nm)\, as
  well as bulk regions\, of ceria-zirconia films. We find that the surface 
 of each of the oxides far is more reduced than the bulk. However\, the ext
 ent to which the surface and bulk regions differ depends strongly on the Z
 r concentration. Specifically\, with increasing Zr\, the differential betw
 een the two regions diminishes. In parallel\, using electrical conductivit
 y relaxation methods\, we find that the bulk chemical diffusion of oxygen 
 decreases in the presence of Zr. These observations can be generally expla
 ined in terms of the preferred lower coordination of the small Zr4+ ion re
 lative to the larger Ce4+ and Ce3+ ions and likely trapping of oxygen vaca
 ncies in the vicinity of Zr. The substantial difference between surface an
 d bulk properties\, where even the trends are reversed\, urges caution in 
 the use of bulk-based properties as surrogate descriptors for surface char
 acteristics.\nBio: Sossina M. Haile is the Walter P. Murphy Professor of 
 Materials Science and Engineering at Northwestern University\, a position 
 she assumed in 2015 after serving 18 years on the faculty at the Californi
 a Institute of Technology. She earned her Ph.D. in Materials Science and E
 ngineering from the Massachusetts Institute of Technology in 1992. Haile
 ’s research broadly encompasses materials\, especially oxides\, for sust
 ainable electrochemical energy technologies. She has established a new cla
 ss of fuel cells with record performance for clean and efficient electrici
 ty generation\, and created new thermochemical approaches for harnessing s
 unlight to meet rising energy demands. Amongst her many awards\, in 2008 H
 aile received an American Competitiveness and Innovation (ACI) Fellowship 
 from the U.S. National Science Foundation in recognition of “her timely 
 and transformative research in the energy field and her dedication to incl
 usive mentoring\, education and outreach across many levels.” She is a f
 ellow of the Materials Research Society\, the American Ceramics Society\, 
 the African Academy of Sciences\, and the Ethiopian Academy of Sciences.
LOCATION:MXF 1 https://plan.epfl.ch/?room==MXF%201
STATUS:CANCELLED
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