Formación de óxidos metálicos semiconductores en carbón activadoCaracterización y aplicaciones

Resum

From a commercial activated carbon (AC; Merck®, 1.5 mm) and six metal oxide precursors (Al3+, Fe3+, Zn2+, SnCl2, TiO2 and WO4 2-), three series of hybrid materials have been prepared by wet impregnation at 80 ºC and oven-drying at 120 ºC (S1) and subsequent calcination at 200 and 850 ºC (S1 and S2). The resulting samples have been characterized in terms of their thermal behaviour, composition, microstructure, texture, morphology, surface chemistry and electrical properties by means of a variety of techniques. In addition, their behaviour as adsorbents for phosphate and nitrate ions in aqueous solution and as electrode materials in supercapacitors has also been investigated. Obtained results reveal the presence in AC of reducing and basic structures, such as pyrone and chromene, which are oxidized to phenolic and carboxylic acid groups. The thermal treatment of S1 causes the release of H2O, CO2 and CO due to dehydration, deshydroxilation and descarboxilation processes and to the carbothermal reduction of the metal oxides. With the temperature rise in the preparation of S1 and S2, chemical changes are more relevant for S3. Moreover, metal hydroxides are converted into oxides, crystallinity improves, particle size distribution broadens and average particle size increases. Textural changes are more significant for S1 and S2, affecting the three porosity regions. Electrical conductivity is essentially determined by the supported phases and its value is the result of a complex interplay between several factors. The behaviour of the prepared samples as adsorbents and as electrode materials is promising.