Modeling NOx Reduction on Catalytic Surfaces with Molecular Beam Techniques

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This proposal is a continuation of Prof. Francisco Zaera's investigation of the catalytic reaction of combustion exhaust gases on noble metal surfaces. Prof. Zaera's laboratory is specialized in the use of molecular beam techniques for intrinsic kinetics determination, and surface infrared vibrational spectroscopy for chemisorbate characterization. Under the previous grant, progress was made in correlating between kinetics and mechanisms observed under high-vacuum to those under catalytic reaction conditions. In the present proposal, NO and CO reactions on Pd (and Rh) single crystals at high temperature will be studied under high-flux pulsed molecular beam conditions, to resemble the real catalytic reaction conditions. In addition, other gases typical in combustion exhaust, e.g., CO2, H2O, O2, will be included in the molecular beam in order to determine the influence of competitive adsorption on the adsorption cross-section and the reaction kinetics. A rapid step-scanning infrared reflection-absorption spectroscope will provide the time-dependent surface coverage and composition information. The mechanism of adsorption will be modeled with Monte-Carlo techniques and the reaction parameters will be derived from the transient kinetics study. This research has significant implications in the development of novel catalysts for the remediation of combustion exhaust gases. It is recognized as a primary need in complying with modern global standards of gas emission.