Pt-metal oxide aerogel catalysts: X-ray photoemission investigation

X-ray photoemission spectroscopy was used to study Pt-metal oxide aerogel c atalysts that have been developed to respond to increased NOx emissions of lean-burn engines. Lean-burn engines, critical components of low and zero e mission vehicles, produce much higher levels of engine-out NOx and current three-way catalytic converters are not sufficient to meet Clean Air Act sta ndards. Platinum catalysts were formed by the reaction of modified Pt coord ination compounds with selected transition- metal alkoxides through sot-gel techniques into aerogels. Photoemission measurements of the Pt 4f, Si 2p, Ti 2p, O 1 s, and C 1s core lines were used to evaluate the chemistry of th e material after each processing step. Results indicate Pt-O bonding and re duced Pt disbursed in the aerogel. In addition, Si 2p, Ti 2p, and O 1s bind ing energies indicate an oxo-bridged network structure. (C) 2001 American V acuum Society.