Synthesis, Characterization, And Photocatalytic Properties Of TiO₂ Semiconductor Based Nanocomposites

In recent years, Energy shortages and environmental pollution have attracted more and more attention, and photocatalytic technology provides a new way to decompose pollutants and generate clean energy by using solar energy. As a common semiconductor photocatalyst, TiO2 has been widely applied in water splitting, degradation of pollutants, sterilization and so on. However, the inherent shortcomings of TiO2 limit its further practical applications, such as narrow light response range, low quantum efficiency, poor recycling activity. In this paper, we focus on preparation of TiO2 based nanocomposites by varying the morphology of the nanostructures and aggregates to better understand the relationship between structure and properties of the TiO2 photocatalysts after surface modification. The main contents are as follows:Firstly, TiO2 hollow spheres with different morphologies are fabricated by using different templates. Glucose derived carbon spheres, resorcinol/formaldehyde resin microspheres(RF), and hollow resorcinol/formaldehyde resin microspheres are prepared, and then used as templates to prepare TiO2 hollow spheres. TiO2 hollow nanospheres with ultra-thin shell, TiO2-C hollow nanospheres and TiO2-C hollow nanospheres with bowl-shape are synthesized respectively by impregnating the above templates with TiF4 solution followed by calcination. The Photocatalytic hydrogen production experiments are carried out to evaluate the activity of these hollow structured photocatalysts. The results show that TiO2-C bowl-shaped hollow nanospheres exhibit higher photocatalytic activity with a hydrogen production rate is about 8mmol h-1g-1.Secondly, TiO2–carbon hybrid nanomaterials with enhanced stable photocatalytic hydrogen production activity are synthesized. Carbon hybridized TiO2 nanosheets(TiO2 NS-C) and carbon hybrized TiO2 nanoparticles(Ti O2 NP-C) are fabricated through heating oleylamine wrapped ultrathin TiO2 nanosheets under argon and air atmosphere, respectively. NOBF4 coated TiO2 nanosheets and TiO2 nanoparticles are also fabricated for comparison. Photocatalytic results show that the activity of these hybrid nanomaterials can be improved and stabilized in comparison to Ti O2 nanomaterials without carbon hybridization no matter what shape(ultrathin nanosheets or nanoparticles) TiO2 presents in the composites.Thirdly, Ni-Fe-layered double hydroxide(Ni Fe-LDH) is used to modify Ti O2 nanobelts and photocatalytic degradation of methylene blue is conducted in the presence of Ti O2/Ni Fe-LDH photocatalysts. P25 powders are used as a precursor to prepare Ti O2 nanobelts with mixed phase of Anatase and Ti O2(B) mixed phase, which are further modified by Ni Fe-LDH to get Ti O2/Ni Fe-LDH nanocomposites with different Ni Fe-LDH loading. Photocatalytic degradation of methylene blue demonstrate that Ni Fe-LDH loading lower the photocatalytic activity of Ti O2 nanobelts under UV light and improve their activity slightly under visible light.