Characterization Studies of Copper Supported on a Variety of Carbonaceous Substrates

Abstract

ABSTRACTCopper catalysts supported on different allotropie forms of carbon, such as activated carbon, graphite, pitch-based carbon fibers and diamond have been prepared and characterized using TPR, XRD, TPO, TEM and CAEM techniques. Preparation procedures were established for each support system and were dependent upon the oxidation characteristics of the particular carbonaceous solid. The ease of the reduction of copper oxide to metallic copper was found to be dependent upon the nature of the carbonaceous supports as well as the possible interactions between these two components. It was postulated that the epitaxial relationship that might exist between metallic copper and the diamond would make it easy for copper oxide to be reduced to its metallic state on this support. Attack of the graphite surface occurs in the presence of copper species in hydrogen at low temperatures. This behavior is rationalized according to the notion that dissociation of molecular hydrogen takes place on Cu2O and the active atomic species “spill-over” onto the graphite and undergo reaction with the π-electrons of the basal plane resulting in the creation of pits in the surface. In-situ electron diffraction highlighted the changes in the chemical state of copper species. Cu2O was found to be stabilized at certain stages of the reaction possibly due to its interaction with the carbonaceous supports. It is suggested that this type of copper species might exhibit some unique catalytic behavioral patterns.