Synthesis and Characterization of Three-Dimensionally Ordered Macroporous Carbon/Titania Nanoparticle Composites

Three-dimensionally ordered macroporous (3DOM) carbon/titania nanoparticle composites were prepared in a program aimed at developing methods for assembling integrated multifunctional porous materials. The host material, 3DOM carbon, was synthesized by colloidal crystal templating with poly(methyl methacrylate) spheres, using a resorcinol−formaldehyde sol as a carbon source. This 3DOM support was pretreated with nitric acid to enhance the surface charge, and surface functional groups were characterized by Fourier transform infrared spectroscopy and acid−base titration. The modified support was then precoated with multiple layers of polyelectrolytes and finally coated with TiO2 nanoparticles using the hydrothermal reaction of an aqueous solution of titanium(IV) bis(ammonium lactato) dihydroxide (TAL) at varying concentrations, temperatures, and reaction times. Higher hydrothermal reaction temperatures favored the formation of larger TiO2 crystallites. The coating thickness increased at higher titanium precursor concentrations. Powder X-ray diffraction patterns indicated that the phase composition of the TiO2 layer varied with different synthesis conditions. Scanning electron microscopy images revealed that the most uniform coating of TiO2 was obtained at a reaction temperature of 200 °C with a TAL concentration of 0.2 M. This sample was characterized in more detail, using transmission electron microscopy, thermogravimetric analysis, differential scanning calorimetry, and nitrogen-sorption techniques.