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Faculty > John M. Vohs John M. Vohs
Carl V. S. Patterson Professor of Chemical and Biomolecular Engineering B.S., Chemical Engineering, University of Illinois, 1983 email:
Current Focus of Research Chemical processes which occur on surfaces and at interfaces are important in a variety of technologies ranging from petrochemical processing and manufacturing to electronic materials. One of the primary foci of the Vohs research group is developing molecular level descriptions of these important surface phenomena. In addition to this work in this area the Vohs group also has ongoing research in the development of solid oxide fuel cells. Brief descriptions of specific research projects are given below. Structure-Activity Relationships for Oxide Surfaces Metal oxides are an important class of materials that are used as catalysts for a variety of reactions of organic molecules including selective and complete oxidations. We are currently studying the relationships between surface structure, composition and the reactivity of metal oxide surfaces. Our goal is to develop molecular level descriptions of the active sites, intermediates, and mechanisms or catalytic reactions on metal oxides. Specific catalytic materials that are currently being studied include ceria which is an important component in automotive emission control catalysts, supported vanadia monolayer catalysts which are used for selective oxidations, and a variety of metal oxides that are used for the oxidation and reduction of organosulfur compounds. Our experimental approach in much of this work relies on the use of well-defined model systems, such as single crystals or thin films that facilitate detailed surface structural and kinetic measurements. Surface reactions and adsorbed species are studied using a battery of ultra-high-vacuum surface analysis techniques including, temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS) and high resolution electron energy loss spectroscopy (HREELS). We also use TPD coupled with thermal gravimetric analysis, FTIR, and calorimetry to study reactions on high surface area materials. Solid oxide fuel cells (SOFCs) have the potential to be highly efficient devices for the conversion of chemical energy in molecules directly into electrical energy. While in recent years much effort has been directed toward the development of fuel cells, most of this work, including that for SOFCs, has focused on systems that require either hydrogen or a hydrogen rich synthesis gas as the fuel. While this approach has some advantages, one disadvantage is the steps that are required to produce hydrogen fuel via reforming of hydrocarbons significantly decrease overall efficiency. Our research in this area has focused on the development of anodes and anode catalysts for SOFCs that allow the direct use of hydrocarbons as the fuel without the need for reforming them to produce hydrogen. Current projects in this area range from fundamental catalytic studies to the development of novel methods for ceramic material processing to fundamental studies of solid state electrochemistry. Awards and Honors
Selected Publications Temperature Programmed Desorption Study of the Oxidation of Methanol to Formaldehyde on TiO2(110)-Supported Vanadia Monolayers, G.S. Wong, D.D. Kragten, and J.M. Vohs, Surface Science, 452 (2000) L293. Direct Oxidation of Hydrocarbons in a Solid Oxide Fuel Cell, S. Park, J.M. Vohs, R.J. Gorte, Nature, 404 (2000) 265. Reaction of NO on CeO2 and Rh/CeO2 Thin Films Supported on a-Al2O3(0001) and YSZ(100), R.M. Ferrizz, T. Egami, G.S. Wong, and J.M. Vohs, Surface Science, 476 (2001) 9. Structure Sensitivity of the Reaction of Methanol on Ceria, R.M. Ferrizz, G.S. Wong, T. Egami, and J.M. Vohs, Langmuir, 17 (2001) 2464. The Oxidation of Methanol to Formaldehyde on TiO2(110)-Supported Vanadia Thin Films, G.S. Wong, D.D. Kragten, and J.M. Vohs, J. Phys. Chem. B, 105 (2001) 1366. An XPS Study of the Growth and Electronic Structure of Vanadia Films on CeO2(111), G.S. Wong and J.M. Vohs, Surface Science, 498 (2002) 266. TPD-TGA and Calorimetric Study of the Partial Oxidation of Methanol on TiO2-Supported Vanadium Oxide, T. Feng and J.M. Vohs, J. Catal., 208 (2002) 301. Oxidation of Methanol to Formaldehyde on Vanadia Films Supported on CeO2(111), G.S. Wong, M.R. Concepcion, and J.M. Vohs, J. Phys. Chem. B, 106 (2002) 6451. TPD and XPS Investigation of the Interaction of SO2 with Model Ceria Catalysts, R.M. Ferrizz, R.J. Gorte, J.M. Vohs, Cat. Lett., 82 (2002) 123. An Examination of Rare-Earth Additives on Performance of Cu-YSZ Cermet Anodes, S. McIntosh, J.M. Vohs, and R.J. Gorte, Electrochem. Acta, 47 (2002) 3815. A Study of Direct-Oxidation SOFC with n-Butane at Higher Fuel Utilization, O. Costas-Nunes, J.M. Vohs, and R.J. Gorte, J. Electrochem. Soc., 150 (2003) A858. Determining the Ce2O2S-CeOx Phase Boundary for Conditions Relevant to Adsorption and Catalysis, R.M. Ferrizz, R.J. Gorte, and J.M. Vohs, Applied Catalysis B: Env., 43 (2003) 273. Synthesis of Highly Porous YSZ by Tape-Casting Methods, M. Boaro, J.M. Vohs, and R.J. Gorte, J. Am. Ceram. Soc., 86 (2003) 395. Reactivity of Monolayer V2O5 Films on TiO2(110) Produced via the Oxidation of Vapor-Deposited Vanadium, G.S. Wong, M.R. Concepcion and J.M. Vohs, Surface Science, 526 (2003) 211. Impedance Spectroscopy for the Characterization of Cu-Ceria-YSZ Anodes for SOFCs, S. McIntosh, J.M. Vohs, and R.J. Gorte, J. Electrochem. Soc., 150 (2003) A1305. A Comparison of Cu-Ceria-SDC and Au-Ceria-SDC Composites for SOFC Anodes, C. Lu, W.L. Worrell, J.M. Vohs, and R.G. Gorte, J. Electrochem. Soc. 150 (2003) A1357. Comparison of the Reactivity of High-Surface Area, Monolayer Vanadia/Ceria Catalysts with Vanadia/CeO2(111) Model Systems, J.M. Vohs, T. Feng, and G.S. Wong, Catalysis Today, 85 (2003) 303.
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