Sessler Lectureship: Professor Andrew A. Gewirth, University of Illinois at Urbana-Champaign
About the Seminar:
"Oxygen Reducation and the Potential Dependent Structure of Water: Surface-Molecule Interactions Relevant to Fuel Cell Catalysis"
In this talk, we discuss two different aspects related to the structure and reactivity of electrode surfaces. First, we report on our efforts directed at establishing the mechanism of oxygen and peroxide reduction on bare Pt and Cu, and on AU surfaces modified with order metal monolayers. By using a combination of spectroscopic, imaging, and x-ray scattering techniques combined with detailed calculations, we have shown that a crucial step involves the spontaneous cleavage of the O-O bond to form a mixed metal-hydroxide complex. This hydroxide complex is reduced during the electron transfer event, leading to the product water. This understanding provides directions for synthesis of advanced catalysts for oxygen reduction. In particular, we have syntehsized a series of metal coordination polymers exhibiting oxygen reduction activity.
Second, we use in situ infrared visible sum frequency generation spectroscopy (SFG) to examine the OH stretching modes of water at the electrified metal/water interace. The SFG shows the presence of different types of water at the interface, the relative abundance of which is potential dependent. These observations are consistent with the flip-flop model for water organization at the interface, wherein the charge at the surface controls water orientation. Measurements conducted in the absence of electrolyte reveal the absence of highly hydrogen-bonded water, which suggests that the electrolyte provides a template to organize water at the interface.
About the Speaker:
Professor Andrew A. Gewirth received his A.B. from Princeton University in 1981 and his Ph.D. from Stanford University in 1987. He joined the Illinois faculty in 1988 after postdoctoral work at the University of Texas, Austin. Now Director of the School of Chemical Sciences at the University of Illinois, Professor Gewirth has received a number of awards, including a Presidential Young Investigator Award, an A.P. Sloan Foundation Fellowship, the Department of Energy Outstanding Accomplishment Award in Materials Chemistry, and the University of Illinois University Scholar Award. His work addresses chemistry at interfaces, especially the solid-liquid interface.