MSE Seminar Series: Gregory S. Rohrer
Friday, January 29, 2010
1:00 p.m.-2:00 p.m.
Room 2108, Chemical and Nuclear Engineering Bldg.
The Dipolar Field Effect and Photochemical Reactions on Titania/Ferroelectric Heterostructures
Presented by Gregory S. Rohrer
W.W. Mullins Professor and Head
Department of Materials Science and Engineering
Carnegie Mellon University
The ability of titania to photochemically split water to produce hydrogen is limited, in part, by the recombination of charge carriers and the back reaction of reduced and oxidized intermediates. The ability of ferroelectric materials with permanent dipoles to separate charge carriers and spatially localize the reduction and oxidation products of photochemical reactions has the potential to increase photolysis efficiency. In this seminar, I will describe photochemical reactions on thin titania films supported by ferroelectric substrates (BaTiO3 and BiFeO3) with a wide range of orientations. The results show that regardless of the phase or orientation of the titania film, the dipolar field from the substrate influences charge carrier motion in the film and causes spatially localized reactivity. For all of the orientations, the thinnest films have reactivities equal to or greater than the bulk-like films, suggesting that the charge separating characteristics of the substrate have the potential to increase the reactivity of titania. The observations are interpreted in terms of a model for the positions of the electronic bands in the heterostructure.
About the Speaker
Gregory S. Rohrer is the W.W. Mullins Professor of Materials Science and Engineering, the Head of the Materials Science and Engineering Department, and the Director of the NSF sponsored Materials Research Science and Engineering Center at Carnegie Mellon University. He received his bachelor's degree in Physics from Franklin and Marshall College in 1984 and his Ph.D. in Materials Science and Engineering from the University of Pennsylvania in 1989. He is the author of over 160 publications and has received the following awards: National Science Foundation Young Investigator Award (1994), Roland B. Snow Award of the American Ceramic Society (1998), Ross Coffin Purdy Award of the American Ceramic Society (2002), Fellow of the American Ceramic Society (2003), the Richard M. Fulrath Award of the American Ceramic Society (2004), and the Robert B. Sosman Award of the American Ceramic Society (2009). Rohrer gave the Lawley lecture at Drexel University in 2005, the Winchell Lecture at Purdue University in 2007, and was the G.E. Distinguished Lecture for MS&E, Rensselaer Polytechnic Institute in 2009. Rohrer is an Associate Editor of the Journal of the American Ceramic Society and was the chair of the Basic Science Division of the American Ceramic Society in 2005 and is on the executive committee of the University Materials Council.