Synthesis of carbon and silica hollow spheres with mesoporous shells using polyethylene Oxide/Phenol formaldehyde polymer blend

Polyethylene oxide/phenol formaldehyde silica composite hollow spheres were obtained from a fast silicification of a polymer blend, containing polyethylene oxide (PEO) as silica gelator and phenol formaldehyde (PF) polymer as carbon source, in a highly diluted silica solution at pH approximate to 5.0-6.0. The PF-PEO/silica hollow spheres can be feasibly converted to mesoporous silica hollow spheres by hydrothermal treatment and calcination, and to mesoporous carbon hollow spheres after pyrolysis under a nitrogen atmosphere and silica etching. Because the formation of the hollow spheres is kinetically controlled, the diameter of the hollow spheres is dependent on the molecular weight of the PEO polymer, pH value of the silica solution, and the PF content, and the size can be tuned within a range of a few micrometers to tens of nanometers, These mesoporous hollow spheres have high surface areas and large pore sizes and volumes. In practice, the mesoporous carbon hollow spheres with an interconnected mesostructure were used as a solid template to prepare different metal oxide hollow spheres. After impregnation of the proper metal oxide precursors and calcination, the y-A1203, anatase-TiO2, alpha-Fe2O3, ZrO2, MgO, and CeO2 hollow spheres composed of nanoparticles were readily synthesize. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007).