A Vibrational Spectroscopic Study of the CO + NO Reaction: From Pd Single Crystals at Ultrahigh Vacuum to Pd Clusters Supported on SiO_2 Thin Films at Elevated Pressures

摘要

Design and development of three-way catalytic converters have received significant scientific attention in the catalysis field due to their commercial importance in automobile exhaust emissions (for the simultaneous reduction of NO, and oxidation of CO and unburned hydrocarbons). Although the reaction between CO and NO has been studied over various transition and noble metal catalysts, only recently Pd-based catalysts have been proposed as an alternative to the Pt/Rh catalysts that are predominantly used. (7,) Hence, a fundamental understanding of the reaction pathways of the CO + NO reaction on Pd surfaces is of vital importance. Adsorption of CO and NO on low index planes of palladium has been studied in detail under ultra-high vacuum conditions, however only a few studies have examined the CO + NO reaction in real time at elevated pressures.(4-8) These studies on a Pd(lll) surface (4-8) have focused on the reaction kinetics and the branching ratio between the desired reaction pathway (1) and the less ideal pathway (2).