Design Synthesis Of Nanostructured Hybrids Of Titanium Dioxide And Titanate

Nanostructured titanium dioxide and titanate are functional inorganic materials, which have important applications in electrochemicalcatalysis, photocatalysis, and ion exchanging. At present, one of the goals in this field is to combine titanium dioxide or titanate with metals, semiconductors and magnets to form heterogeneous nanostructures, which can improve their properties. In this thesis, we demonstrate the synthesis of titanate/Au and titanate/Pd nanotube bundles, Ag/TiO2 nanoribbons and Fe3O4/Na2Ti3O7 nanosheets, and investigate their electrocatalytical activity, photocatalytic activity, and ion exchanging performance.(1) Preparation of titanate/Au and titanate/Pd nanotube bundles and their catalytical activity towards the electrochemical oxidation of methanol: Through the reaction between TiO2 crystallites and highly concentrated NaOH in the presence of Au or Pd sols, titanate/Au and titanate/Pd nanotube bundles were synthesized. Due to the unique scrolling growth mechanism of titanate nanotubes (TNTs), Au or Pd clusters were encapsulated in situ by TNTs. In comparison with carbon nanotubes (CNTs) or active carbon that were widely used as carriers to support metal clusters, TNTs bundles can immobilize the metal cluster tightly and overcome the shortcoming of exfoliation of metal clusters from the carriers. The as-prepared titanate/metal hybrids possess mesoporosity and high surface area. The electrochemical oxidation of methanol demonstrates that titanate/Pd hybrids exhibit high electrocatalytic activity and excellent stability, and hence they should be ideal catalyst candidates in direct methanol fuel cells (DMFCs).(2) Preparation of Ag/TiO2 nanoribbons and photocatalytic activity: Through the one-pot hydrothermal reaction of Ag and TiO2 with NaOH and the post treatment of acid washing and calcination, uniform Ag@TiO2 nanoribbons were synthesized on a large scale. The morphology of Ag@TiO2 was interesting: the interior of the nanoribbon has rich pores and Ag clusters were distributed homogeneously on the surface of the nanoribbons. The average width of Ag@TiO2 nanoribbons was 50 nm and their lengths can reach several tens of micrometers. The combination of Ag clusters with TiO2 nanoribbons not only increases the optical absorption efficiency of TiO2, but also facilitates the separation of the photo-generated charges. Consequently, Ag@TiO2 nanoribbons can induce the complete photo-degradation of methylene blue in a shorter time than isolated TiO2 nanoribbons.(3) Preparation of Fe3O4/Na2Ti3O7 nanosheets and ion exchanging performance: Through a co-reaction of Fe and TiO2 with concentrated NaOH, free-standing Na2Ti3O7 nanosheets grown epitaxially by Fe3O4 crystallites were successfully synthesized in an extremely high yield ( 95% efficiency). Fluorescein and its derivatives utilized as probes to study the ion exchange property of Fe3O4@Na2Ti3O7 nanosheets, which could provide visual observations of the degree of ion exchange. The results indicate that the as-prepared Fe3O4@Na2Ti3O7 nanosheets possess much more sensitive Na+ exchange performance than isolated Na2Ti3O7 nanostructures.