Oxide Nanomaterials for Energy Applications
PI: Stanislaus Wong
In my group, we have been focused on several key nanosclence issues. We have a strong effort in the chemicai functionalization of carbon nanotubes. In addition, we have a growing program in the synthesis and characterization of nanoscale metal oxide materials, related to energy applications. Examples include the following:
- Three-dimensional, dendritic micron
scale spheres of alkali metai hydrogen titanate 10 nanostructures (i.e,: nanowires and nanotubes) have been generated using a modified hydrothermal technique in the presence of hydrogen peroxide and an alkali metai hydroxide solution. Sea-urchin-like assemblies of these 1D nanostructures have been transformed into their hydrogen titanate analogues (Iepidocrocite HxTi2-x/4j'ix/404 (x-O.?, fi: vacancy)) by neutralization as well as
into their corresponding anatase Ti02 nanostructured counterparts through a moderate high-temperature annealing dehydration process without destroying the 3D hierarchical structural motif. The as-prepared hollow spheres of titanate and titania 1D nanostructures have overall diameters, ranging from 0.8 £gm to 1.2 £gm, while the interior of these aggregates are vacuous with a diameter range of 100 to 200 nm. We have demonstrated that these assemblies are active photocatalysts for the degradation of synthetic Procion Red dye under UV light illumination. - A size and shape-dependent morphologica transformation was demonstrated during the hydrothermal soft chemical transformation, in neutrai solution, of titanate nanostructures into their anatase titania counterparts. Specifically, protonic lepidocrocite hydrogen titanate nanotubes with diameters of ~10 nm were transformed into exceptionally high-purity anatase nanoparticles with an average size of 12 nm. Lepidocroclte hydrogen titanate nanowires with reiatively small diameters (average diameter range of T 200 nm) were converted into singlecrystalline anatase nanowires with
relatively smooth surfaces. Larger diameter (>200 nm) titanate nanowires were transformed into analogous anatase nanowire motifs,
resembling clusters of adjoining anatase nanocrystals with perfectly parallel, oriented fringes, Our results indicate that as-synthesized TiO2
nanostructures possessed higher photocatalytic activity than the commercial titania precursors from whence they were derived.