Surface Chemistry: Catalysis, Photochemistry, Reaction Kinetics & Dynamics
Catalysis is an essential technology supporting our way of life and contributes towards roughly 1/3 of the material GDP of the US economy. At the beginning of the 20th Century, the catalytic transformation of nitrogen on nanoscale, potassium promoted, iron catalysts to ammonia, and ultimately fertilizer, profoundly changed the human condition and currently supports an additional 2.4 billion people beyond what the Earth could otherwise sustain. In the 21st Century, the catalytic challenge will be to facilitate a rapid transition from a petroleum-based energy and chemical economy to a more generalized one based on natural gas, hydrogen, coal, biomass, and solar energy (photochemistry). Energy efficient chemical transformations, environmental protection, and green chemistry will continue to rely heavily on catalysis. Most industrially viable catalysis takes place on the surfaces of transition metal nanocrystallites dispersed on oxide supports. Our research focuses on understanding gas-surface reactions on simplified scientific model surfaces, namely, on single crystal surfaces. Recent progress includes the development of quantitative models for (i) the C-H bond activation of CH4 on metal surfaces that relates to the industrial production of H2 via natural gas reforming on metal nanocatalysts, and (ii) the chemical vapor deposition of Si on Si (100) by SiH4 that is central to Si homoepitaxy in microelectronics manufacturing. Current activities focus on exploring the thermal and photochemical reaction dynamics of catalytically important and energy-related small molecules, such as H2, CO2, CH4, alkanes, and alcohols, on transition metal surfaces. Our research typically employs ultrahigh vacuum surface analytical techniques (e.g., TPD, AES, XPS, RAIRS, STM, LEED) as well as some more specialized laser techniques (SFG, TOF) and/or microcanonical unimolecular rate theory. Our goal is to characterize the transition states of important catalytic reactions and to develop an improved understanding of how to design efficient & selective thermal and photochemically driven catalysts.
Angle-resolved thermal dissociative sticking of CH4 on Pt(111): Further indication that rotation is a spectator to the gas-surface reaction dynamics. J. K. Navin, S. B. Donald, D.G. Tinney, G. W. Cushing, and I. Harrison, J. Chem. Phys. 136, 061101 (2012)
Dynamically biased RRKM model of activated gas-surface reactivity: vibrational efficacy and rotation as a spectator in the dissociative chemisorption of CH4 on Pt(111). S. B. Donald and I. Harrison, Phys. Chem. Chem. Phys. 14, 1784-1796 (2012)
An Effusive Molecular Beam Technique for Studies of Polyatomic Gas-Surface Reactivity and Energy Transfer. G. W. Cushing, J. K. Navin, L. Valadez, V. Johánek, and I. Harrison, Rev. Sci. Instr. 82, 044102 (2011).
C-H Bond Activation of Light Alkanes on Pt(111): Dissociative Sticking Coefficients, Evans-Polanyi Relation, and Gas-Surface Energy Transfer. G. W. Cushing, J. K. Navin, S. B. Donald, L. Valadez, V. Johanek, and I. Harrison. J. Phys. Chem. C. 114, 17222-17232; 22790 (2010).
Methane Dissociative Chemisorption on Ru(0001) and Comparison to Metal Nanocatalysts. H. L. Abbott and I. Harrison. J. Catal. 254, 27-38 (2008).
Microcanonical Transition State Theory for Activated Gas-Surface Reaction Dynamics: Application to H2/Cu(111) with Rotation as a Spectator. H. L. Abbott and I. Harrison. J. Phys. Chem. A. 111, 9871-9883 (2007).
Activated Dissociation of CO2 on Rh(111) and CO Oxidation Dynamics. H. L. Abbott and I. Harrison. J. Phys. Chem. C. 111, 13137-13148 (2007).
Sum frequency generation from planar and porous silicon in contact with liquids. K. W. Kolasinski, K.M. DeWitt, and I. Harrison. Phys. Stat. Sol. (a). 204, 1356-1361 (2007).
CH3Br Structures on Pt(111): Kinetically Controlled Self-Assembly of Weakly Adsorbed Dipolar Molecules. T. C. Schwendemann, I. Samanta, T. Kunstmann and I. Harrison. J. Phys. Chem. C. 111, 1347-1354 (2007).