No abstract

No abstract

No abstract

No abstract

A series of carbon xerogels doped with different percentages of TiO2 has been studied as a tentative means of preparing electrodes for supercapacitors.

N-doped carbon xerogels were obtained from organic xerogels prepared using different N-containing organic compounds, including 3-hydroxy aniline, melamine, and 3-hydroxy pyridine. Carbonization was carried out between 500 and 900 degreeC. The surface chemistry of samples was determined by elemental analysis and X-ray photoelectron spectroscopy, their porous texture was determined by N2 and CO2 adsorption at (-)196 and 0degreeC, respectively, and their morphology was determined by scanning electron microscopy. N-doped carbon xerogels with a wide variety of N contents and functionalities were obtained according to the ingredients and carbonization temperature used. Carbon xerogels contained, in different proportions, three/four N functionalities: pyridinic, pyrrolic and/or pyridonic, and quaternary N functionalities. They were microporous carbons with narrow micropores that had constrictions at their entrances, producing higher CO2(-) than N2-determined micropore surface areas. Morphology studies showed samples to be constituted by isolated microspheres or microsphere clusters. Microsphere diameters depended on the recipe and carbonization temperature used.

Fe, Co, Ni, and Cu-doped monolithic organic aerogels were prepared by the sol−gel method through the polymerization of a resorcinol formaldehyde mixture containing the metal acetates as polymerization catalysts. The aerogels were supercritically dried with carbon dioxide, and their surface morphology and pore texture were characterized by means of scanning electron microscopy, N2 adsorption at −196 °C, and mercury porosimetry. The dispersion, distribution, and chemical nature of the metal-containing phase were analyzed by X-ray diffraction, backscattering electron imaging, energy-dispersive X-ray, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. According to these analyses, the surface morphology and pore texture were influenced by the metal acetate present because of its different catalytic activity and pH of the initial mixtures. The metal-containing phase was very highly dispersed in Co and Ni-doped monolithic organic aerogels, and it was homogeneously distributed in Fe and Cu-doped monolithic organic aerogels although not so highly dispersed. XPS studies provided experimental evidence of the chelation of iron and cobalt ions by the phenolic groups of the polymeric matrix but no clear evidence of the chelation of nickel and copper ions.

No abstract