Preparation Of TiO₂ Based Photocatalysts And Their Applications In Fuel Cell And Photodegradation

Fossil energy depletion and environmental pollution have brought serious damage to the human health and social development. In recent years, great research efforts have been devoted to the development and utilization of clean and renewable energy and the restoration of environment. As renewable energy resource, solar energy shows promising prospects in many applications. TiO₂ shows unique advantages of abundant, non-toxic, high stability, high reactivity, which is considered as one of the most ideal and efficient photocatalyst. In this thesis, we have prepared TiO₂ composite materials with excellent performance by controlling the morphology, combing with graphene or coating polyaniline. The catalytic properties of these newly developed TiO₂ based photocatalysts were also examined. Moreover, we have proposed a conceptual photoelectrohemical methanol fuel cell based on TiO₂ composite materials, which realizing the synergetic conversion of solar energy and chemical energy into electricity. And, the newly prepared photocatalyst was used to degrade organic matter in water under the assist of sunlight, which realizing the application of TiO₂ based photocatalysts in new energy utilization and environmental restoration.（1） By hydrothermal method and high temperature reduction treatment, we have prepared 3D nanostructured aligned TiO₂ nanorods decorated graphene composites（G-TNRs）. Compared with pure TiO₂ nanorods（TNRs）, photocatalytic performance of G-TNRs was improved nearly 7 times. Under 360 nm UV irradiation, in 0.5 M Na2SO4 with 1.0 M methanol, the photocurrent can reach to 2 μA?cm-2. Moreover, a fuel cell was constructed with G-TNRs as the anode, methanol as fuel, oxygen reduction catalyst as cathode. It can realize the transformation of chemical energy into electrical energy with the assistance of solar. Under illumination of 60 mW natural light, the open circuit voltage and power density of PEC methanol fuel cell can reach 0.615 V and 1.1 μW?cm-2, respectively. This work not only offered insights into the design of functional nanomaterials with controllable properties and morphology, but also provided new energy technology, photoelectrochemical fuel cells.（2） We have prepared mesoporous TiO₂ nanofibers using the electrostatic spinning technique, and then coated polyaniline on mesoporous TiO₂ nanofibers by the method of chemical oxidative polymerization. In the process of electrostatic spinning, we introduced the pore-forming agent and produced the TiO₂ nanofibers with mesoporous structure. Then, we have investigated the effect of coating quantity on the photocatalytic activity of the PANI-TiO₂ composite. It was found that a moderate coating amount of polyaniline can improve the performance of photocatalyst by 3 times. Under illumination of 50 mW natural light, in 0.5 M H2SO4 with 0.3 M formic acid, the photocurrent can reach to 5 μA?cm-2. Furthermore, this study also explored the PANI-TiO₂ composite photocatalytic degradation of formic acid. The photocurrent increased from 2.5 μA?cm-2 to 5 μA?cm-2 with the concentration of formic acid increased from 0.2 M to 0.3 M.Overall, the performance of TiO₂-based photocatalysts was improved significantly by reasonable structure tuning and morphology modification. Also, we have substantially expanded the reasonable applications of TiO₂-based photocatalysts.