Optical studies of high temperature surface chemistry
The overall goal of this project is to identify the mechanisms responsible for electrochemical oxidation in solid oxide fuel cells (SOFCs). Due to the high activation energy needed to catalyze molecular oxygen dissociation and the small diffusion constants associated with oxide ion transport through doped, metal-oxide ceramics, SOFCs must operate at elevated temperatures – typically 650˚C or higher. Traditional studies of SOFC operation use electrochemical techniques to report on system performance, but these data can not differentiate the chemical species responsible for observed behavior. Samples used in these studies are often subjected to exhaustive, ex situ, post mortem analyses. Thus, researchers are left to infer how chemical and structural changes observed after operation correspond to electrochemical performance measured during operation. To overcome the challenges associated with making measurements at high temperatures and under strongly reducing or oxidizing conditions, my group has built and adapted instrumentation to acquire vibrational Raman spectra from metal and metal oxide surfaces at temperatures in excess of 750˚C (!).
M. B. Pomfret, J. C. Owrutsky, and R. A. Walker, "High Temperature Raman Spectroscopy of Solid Oxide Fuel Cell Materials and Processes." J. Phys. Chem. B 110 17305-17308 (2006).
M. B. Pomfret, J. C. Owrutsky, and R. A. Walker , "In-situ Studies of Fuel Oxidation in Solid Oxide Fuel Cells." Analytical Chemistry 79 2367-2372 (2007)
M. B. Pomfret, J. Marda, G. S. Jackson, B. W. Eichhorn, A.M. Dean and R. A. Walker , "Hydrocarbon fuels in solid oxide fuel cells: In-situ Raman studies of graphite formation and oxidation." J. Phys. Chem. C 112, 5232-5240 (2008)
M. B. Pomfret, B. C. Eigenbrodt, and R. A. Walker, "Interfacial Resistivity of Yttria Stabilized Zirconia in Operating Solid Oxide Fuel Cells." Electrochemical Society Transactions, 11 (27) 111-120 (2008)