Abstract (EN):
Activated carbons have a disordered graphitic structure, which has been described as compared to to wrinkled paper sheets. The presence of heteroatoms (such as O, N, H, S, etc) bound to the edges of the graphene layers originates a variety of surface functional groups. Oxygenated functionalities have been most extensively studied, since they are formed spontaneously by exposure of the carbon material to the atmosphere; however, nitrogen, sulfur and phosphorous groups can also be found. The nature and concentration of surface functional groups may be modified by suitable thermal or chemical treatments. Treatments in the gas or liquid phase can be used to increase the concentration of surface groups, while heating under inert atmosphere may be used to selectively remove some of those functionalities. A variety of experimental techniques has been used to characterise functional groups, such as chemical titration methods, temperature-programmed desorption, X-ray photoelectron spectroscopy and infra-red spectroscopy methods. The results obtained by temperature-programmed desorption agree quantitatively with the elemental and proximate analyses of the oxidized materials, and qualitatively with the observations by infra-red spectroscopy. Some applications of functionalised activated carbons in adsorption and catalysis for several reactions are mentioned.
Language:
English
Type (Professor's evaluation):
Scientific