Manipulated Preparation And Characterization Of Titanium Dioxide Based Photocatalytic Materials

The continuous growth of human population and advanced industrialization comes up with negative effects on the environment. Numerous research efforts have been devoted on developing ways of cleaning up the environment. Photocatalytic effect of TiO₂ semiconductor was discovered in 1970s and found it as a promising solution towards environmental pollution. Since that time, the technologies of photocatalysis are continuously developing. Titanium dioxide is a promising photocatalyst for energy and environmental demands due to its inspiring physical and chemical characteristics. In spite of that, quantum efficiency of TiO₂ is tremendously hindered by efficient electron-hole recombination and limited visible light absorption due to its larger band gap of 3.2 eV. Therefore, there is a crucial aim to improve TiO₂ photocatalysis performance under UV as well as visible light irradiation through designing an appropriate model system.The main focus of this work is to manipulate titanium dioxide based materials so as to make it useful at industrial level for the environment protection. This work also investigates visible light active photocatalysts including nanocomposites and metal plasmonic catalyst. These modified designs were helpful to retard the recombination of photoinduced charge carriers, promote surface assimilation of organic pollutant and consequently increase the photocatalytic activity of the heterostruture photocatalyst. The detailed descriptions about the prepared heterostructure are listed below.In the first approach, a model consisting in the form of one dimensional TiO₂ nanofibers ?TNFs? with different anatase/rutile phase ratios were fabricated using electrospinning technique followed by the annealing at different temperatures. The effect of annealing temperatures on their morphology, structural and optical properties and photocatalytic activity was investigated. The photocatalytic performance of TNFs was evaluated by degradation of methyl orange ?MO? in aqueous solution under the irradiation of simulated solar light. Annealing temperature significantly influenced photocatalytic degradation of MO due to the incorporation of rutile phase which suppresses recombination of photoactivated electron and hole pairs. Turnover frequency ?TOF? of MO degradation was introduced to describe the intrinsic activity of TNFs. TNFs acquired best anatase/rutile phase ratio ?A/R=83/17? when annealed at 650?, resulting in highest TOF value 2394 h-1, two times higher as compared to P25 with similar anatase/rutile phase ratio ?A/R=85/15?. Appropriate crystalline structure could be the reason for good photocatalytic activity as well as intrinsic activity of TNFs.Multi-walled carbon nanotubes-titanium dioxide ?MWCNTs-TiO₂? nanocomposites were synthesized via microwave-assisted synthesis and conventional hydrothermal method, comprising of well-crystallized anatase TiO₂ nanoparticles with different MWCNTs contents. TiO₂ nanoparticles synthesized by the rapid thermal decomposition of tetra-butyl titanium ?Ti?OC₄H₉?₄? in the presence of acid treated MWCNTs, were attached on the surface of MWCNTs by means of chemical bonds under microwave irradiation. The addition of MWCNTs did not influence the structure of anatase TiO₂. The photocatalytic performance evaluation of composite materials was conducted under UV and visible light using methyl orange ?MO? as a typical pollutant. The enhancement in photocatalytic efficiency of nanocomposites was clearly observed by the presence of MWCNTs, which could contribute to improve the adsorption of MO dye, extend the light absorption range and also obstruct the photogenerated electron-hole pair's recombination.A novel ternary Ag/AgCl/TiO₂?B? nanosheets photocatalyst is rationally designed to obtain good visible light spectrum response and high charge separation efficiency simultaneously for TiO₂-based photocataylsts. TiO₂?B? nanosheet is adopted to accelerate the charge separation, while the Ag/AgCl plasmonic photocatalyst could enhance the light absorption via the surface plasmon resonance. The Ag/AgCI/TiO₂?B? nanosheets photocatalyst was prepared by a two-step route, including a controllable heterogeneous precipitation process to obtain AgCl nanocubes anchoring to TiO₂?B? nanosheets, and an in-situ photoreduction to generate Ag nanoparticies on the exterior of AgCl nanocubes. Furthermore, the size of AgCl nanocubes ranging from 50 nm to 300 nm can be tuned by slowing down the rapid growth between the silver and chloride ions via controlling the addition of Cl-source. As-prepared Ag/AgCl/TiO₂?B? nanosheets photocatalyst exhibits superior visible-light photocatalytic activity for the deterioration of methyl orange ?MO?. Its high photocatalytic performance is attributed to the synergistic effects from Ag/AgCl and TiO₂?B? nanosheets.