Nanomaterial characterization and synthesis for solar energy utilization and hydrogen fuel generation

摘要

Semiconducting metal oxide nanowires represent a class of novel materials that are of superior properties to naoparticles currently used in dye sensitized solar cell and polymer hybrid solar cells. The quasi one-dimensional nanostructure and surface states of nanowires improve carrier mobility and charge transfer through interface interactions of theses nanocomposite materials. Raman spectroscopy, especially resonant Raman spectroscopy, is used to correlate nanomaterial synthesis condition to the structural, optical and electric transport properties that are important to photocatalysis, exciton transport and recombination and hydrogen storage mechanism. For example, highly orientated ZnO nanowires studied with Raman and photoluminescence spectroscopy demonstrated the high efficiency of the phonon and electron coupling. These results are compared with that of other ZnO forms such as thin film, polycrystalline powder and solid. The Raman bandwidths and shifts of nanowires revealed the phonon confinement in the quasi one-dimensional nanostructures, which is further demonstrated with In2O3 nanowires at 5, 10, 20, 30 nm in diameters. Room temperature photoluminescence results also show band gap shifts with nanowire dimensions. Nanowire sizes, defects and strains, controlled by synthesis conditions, have shown to determine band structure and optical phonon properties. We also discuss characterization and synthesis of carbon nanotube based composite materials including polymer electropolymerization and infiltration. Combining significantly enhanced mechanical compressive strength and excellent electric conductivity, these composite materials offer potentials to fuel cell anode materials as multifunctional hydrogen storage media.