| Summary: |
Carbon nanofibers are cylindric nanostructures containing graphene layers arranged as stacked cones, cups or plates. Carbon nanotubes are a particular type of carbon nanofibers where graphene layers are wrapped longitudinally into perfect cylinders, either single (single-wall) or concentric (multi-wall). Low-cost carbon nanofibers with diameters in the 100-200nm range can be produced from the catalytic decomposition of hydrocarbon gases or carbon monoxide over selected metal particles that include iron, cobalt nickel, and some of their alloys at temperatures over the range 400-1000°C; this process is termed catalytic chemical vapour deposition.
Thanks to their textural characteristics, mechanical resistance and chemical inertia, carbon nanofibers are a priori good candidates for environmental control processes, where they can act as supports for nanometer-sized catalyst particles. However, chemical inertia, which is a positive attribute of a catalyst support as undesired side-reactions are avoided, can be detrimental to the anchoring of metal catalyst precursors. Therefore, controlled functionalization of the nanofibers must be carried out prior lo attachment (by covalent bonding or van der Waals forces) of different types of compounds containing the catalytically active component. This makes it necessary to develop and use methods to characterize on a very local scale the effects of surface modification treatments on carbon nanofiber supports and to identify the compounds formed when catalyst precursors are bound to the functionalized nanocarbons.
Investigation of the metal compound/modified carbon support interaction is aimed at optimizing the characteristics of surface sites and their chemical homogeneity. This more fundamental part of the project is absolutely necessary in order lo establish the most probable mechanism of the catalytic reactions taking place at the surface of carbon nanofiber-based catalysts. Therefore, in this phase of the project,  |
Summary
Carbon nanofibers are cylindric nanostructures containing graphene layers arranged as stacked cones, cups or plates. Carbon nanotubes are a particular type of carbon nanofibers where graphene layers are wrapped longitudinally into perfect cylinders, either single (single-wall) or concentric (multi-wall). Low-cost carbon nanofibers with diameters in the 100-200nm range can be produced from the catalytic decomposition of hydrocarbon gases or carbon monoxide over selected metal particles that include iron, cobalt nickel, and some of their alloys at temperatures over the range 400-1000°C; this process is termed catalytic chemical vapour deposition.
Thanks to their textural characteristics, mechanical resistance and chemical inertia, carbon nanofibers are a priori good candidates for environmental control processes, where they can act as supports for nanometer-sized catalyst particles. However, chemical inertia, which is a positive attribute of a catalyst support as undesired side-reactions are avoided, can be detrimental to the anchoring of metal catalyst precursors. Therefore, controlled functionalization of the nanofibers must be carried out prior lo attachment (by covalent bonding or van der Waals forces) of different types of compounds containing the catalytically active component. This makes it necessary to develop and use methods to characterize on a very local scale the effects of surface modification treatments on carbon nanofiber supports and to identify the compounds formed when catalyst precursors are bound to the functionalized nanocarbons.
Investigation of the metal compound/modified carbon support interaction is aimed at optimizing the characteristics of surface sites and their chemical homogeneity. This more fundamental part of the project is absolutely necessary in order lo establish the most probable mechanism of the catalytic reactions taking place at the surface of carbon nanofiber-based catalysts. Therefore, in this phase of the project, the nanomaterials will be conveniently characterized, both at the structural and molecular levels, using a number of surface chemical techniques available at the participating laboratories in Portugal and Spain.
The project will have other more applied objectives connected with the use of the synthesized nanocatalysts in several reactions of environmental interest, such as the catalytic oxidation of organic compounds present in polluted waters by catalytic wet air oxidation, catalytic ozonation, and electro-oxidation, selective reduction of aromatic groups of the organic pollutants aiming for their transformation into biodegradable compounds and nitrate removal in water by catalytic reduction with hydrogen. The final objective of these kinetic/catalytic studies is to obtain nanocatalysts with higher acclivity and selectivity for the studied processes, in comparison with commercially available catalysts, which are generic and have nol been designed for a specific reaction or process. |