Chemistry Seminar - Designing New Heterogeneous Catalysts Through Metal-Metal Interactions

Designing New Heterogeneous Catalysts Through Metal-Metal InteractionsDr. Donna ChenDepartment of Chemistry and BiochemistryUniversity of South CarolinaRIT SCMS AlumnaAbstract:Bimetallic catalysts often exhibit superior activity compared to their monometallic counterparts. The bimetallic Pt-Re system has been used for decades in industrial reforming reactions, and more recently Pt-Re catalysts have demonstrated enhanced activity for the water gas shift (WGS) reaction and aqueous phase reforming of polyols. However, the exact origins of the superior activity of Pt-Re over pure Pt are not fully understood; specifically little is known about the role of oxidized Re under reaction conditions. In order to understand this improved activity of Pt upon addition of Re, it is necessary to control bimetallic cluster composition, cluster sizes and oxidation states of the Re, as well as to probe Re oxidation states under reaction conditions. We have prepared and characterized Pt-Re bimetallic clusters on titania, which is the most active support for WGS. Experiments were carried out in an ultrahigh vacuum chamber directly coupled to a microreactor so that activity could be evaluated under catalytically relevant pressures while surfaces could be characterized using X-ray photoelectron spectroscopy and infrared absorption reflection spectroscopy before and after reaction. The greatest WGS activity was observed for surfaces consisting of Pt on Re. While the presence of rhenium oxide did not improve catalytic activity, Pt-Re interactions were found to decrease CO poisoning on the bimetallic catalyst. The role of metal-support interactions was investigated by depositing bimetallic clusters on a non-interacting graphite support.Speaker Bio:Donna Chen is Professor of Chemistry and Biochemistry at the University of South Carolina in Columbia and has a courtesy appointment in the chemical engineering department. She received her B.S. degree in chemistry with highest honors from the Rochester Institute of Technology, and received her Ph.D. in physical chemistry from Harvard University under the direction of Cynthia Friend. After two years as a postdoctoral associate at Sandia National Laboratories in Livermore working with Kevin McCarty and Robert Hwang, Donna joined the faculty at the University of South Carolina in 1999. Research in the Chen group has focused on understanding the nucleation, growth and chemical activity of supported metal nanoclusters as models for the development of heterogeneous catalysts. Her work combines detailed understanding of surface properties using ultrahigh vacuum techniques with microreactor and ambient pressure electron spectroscopy studies. Donna is the recipient of the NSF CAREER Award, Army Young Investigator Award, International Precious Metals Institute Carol Tyler Award, South Carolina Governor's Young Researcher Award and University of South Carolina Educational Foundation Research Award. In addition, she has received the University of South Carolina's Ada B. Thomas Outstanding Advisor Award and Mungo Distinguished Professor Award for undergraduate teaching. She is a fellow of the American Association for the Advancement of Science (AAAS) and the American Vacuum Society (AVS).