Research Overview

The chemistry and physics of solid surfaces play a vital role in many technologically important processes ranging from catalysis and corrosion to the operation of microelectronic devices. The experimental tools of ultrahigh vacuum (UHV) surface science provide a unique means of characterizing the top few atomic layers of a solid surface in terms of geometric and electronic structure, and therefore can provide insights into the fundamental chemical and physical processes occurring at solid surfaces.

Our experimental work deals with the chemistry of metal oxide and transition metal carbide and phosphide surfaces. For the oxides, our particular emphasis is on their application to catalytic selective (partial) oxidation, alkane dehydrogenation, and (de)halogenation and halogen exchange reactions. For the transition metal carbides and phosphides, our emphasis is on the heteroatom removal reactions associated with hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) chemistry important in fuels production.

The experimental work in our laboratory utilizes geometrically-ideal model catalysts (single crystal surfaces) to facilitate the study of the effects of surface structure, composition, and oxidation state on the activity and selectivity of catalytic reactions of organic molecules on surfaces. To develop an understanding of these processes at the molecular level, experimental tools such as X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS), Auger electron spectroscopy (AES), ion-scattering spectroscopy (ISS), scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED) are used both for the characterization of clean surfaces and the characterization of adsorbed molecular species and reaction intermediates. Thermal desorption spectroscopy (TDS) with mass spectrometric detection is the primary tool used to investigate the reactivity and kinetics of surface reactions.

Computational work is also conducted by our group to provide insight into phenomena similar to those under experimental study in our laboratory. Density Functional Theory is being used to investigate the chemistry of a number of bulk and surface metal oxide systems. We are interested in phenomena including the geometric and electronic consequences of defect and impurity introduction in oxide systems. The topology of the the Electron Localization Function is currently being used to understand the nature of the chemical driving forces for relaxations and reconstructions at metal oxide surfaces in terms of the local coordination and electronic structure of surface cations and anions.