The effect of graphitic platelet orientation on the properties of carbon nanofiber supported Pd catalysts prepared by ion exchange

Carbon nanofibers with different nanostructures are prepared by catalytic CVD at 873 K using different catalysts and carbon-containing gases. As-grown carbon nanofibers are treated in concentrated nitric acid to introduce oxygen-containing groups, and therefore, to anchor palladium. The TPD-MS method is used to determine the number of acidic oxygen-containing groups and the results show that the number of oxygen-containing groups was strongly dependent on the graphitic platelet orientation. TEM, CO pulse chemisorption, and ICP-AES are used to characterize carbon nanofiber supported palladium catalysts. The results show that palladium particle sizes and palladium loading are dependent on the amounts of oxygen-containing groups on carbon nanofibers. TPR results show that the interaction between the palladium and the oxidized carbon nanofibers can be tailored by the variation of graphitic platelet orientation. A linear correlation between the amount of acidic groups and the palladium loading are observed.