The Effect of Surface Functional Groups on the Dispersion, Chemical Properties, and Catalytic Behavior of Carbon- Supported Pd and Pt-Sn Catalysts Prepared from Metal Cluster

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This is a study of the effects of different oxygen-containing functional groups on the dispersion, sinter resistance, and catalytic behavior of palladium on carbon and of platinum-tin on carbon. The strategy is to alter, in a controlled way, the concentrations of carboxyl, lactone, carbonyl, hydroxyl, and phenolic groups on a high-purity carbon. Historically, attempts to do this have been frustrated by the difficulty of characterizing carbon surfaces. In this study, carbon surfaces are characterized by reflection infrared spectroscopy, thermal gravimetric analysis /mass spectrometry, and differential microcalorimetry after treatment at 1000> to remove all surface groups and after treatments in air, nitric acid, and hydrogen peroxide to selectively restore certain groups. Novel approaches to the preparation of metal/carbon catalysts involve the synthesis and impregnation of palladium and platinum-tin organometallic complexes that can be easily reduced at low temperatures. The influence of palladium crystallite size on magnetic and chemical properties is determined by magnetic susceptibility measurements, heats of adsorption for oxygen, carbon monoxide, and hydrogen on the metal, infrared spectra of chemisorbed carbon monoxide, and solid-state magic-angle-spinning nuclear magnetic resonance of chemisorbed hydrogen as well as palladium-105. The work addresses directly the performance of carbon- supported noble-metal catalysts, but the results are also relevant to production and use of carbon electrodes, coal gasification, and petroleum reforming. Carbon-supported noble-metal catalysts are widely used in the specialty chemicals and petrochemicals industries.