| Nowadays, with the rapid development of industrialization and urbanization, the environmental pollution is becoming more and more serious. In order to realize the sustainable development, it is urgent to prevent and cure the pollution of water and air. T1O2 is a promising catalysts material, which has some advantages such as low cost, no pollution and good chemical stability. And graphene as a new carbon material, has excellent performance in the electrical, optical and so on. Modifying TiO2 the with graphene can effectively inhibit the recombination of photoinduced electron and hole, reinforced photocatalytic properties and gas sensing properties, as well as increase the adsorption properties of composites. In addition, there will be more reactive sites by doping nitrogen into composites, which can further improve the performance of the composite. Therefore, in this thesis, nitrogen doped graphene and TiO2 composites were synthesized and investigated. The main results are as follows:(1) Graphene oxide was synthesized via modified Hummers method. Then, using GO and p-phenylenediamine, the amino graphene was prepared via chemical bath deposition. The amino graphene was characterized by series of analysis, paving the way for the subsequent study of the N-RGO/TiO2 composites. The results showed that graphene oxide has been reduced to graphene after water bath, and there are a large number of amino groups exist in amino graphene surface. The amino groups can control the TiO2 particle size of composites, and also can be the nitrogen source for N doping.(2) Using titanium sulfate and amino graphene as precursors, hydrofluoric acid as the morphology control agent, the N-RGO/TiO2 composite have been synthesized via hydrothermal method. By analyzed the morphology of different composites, the influences of HF and amino graphene was discussed. The prepared composites were characterized by XRD, XPS, SEM and so on. The results indicated that the N elements were doped into composites, and RGO and TiO2 were connected by chemical bond. The structure of TiO2 was truncated octahedron bipyramid with two {001} and eight{101} facets, and a surface heterojunction between two facets. With the increase of amino graphene content, the particle size of TiO2 become smaller and scattered more uniform.(3) The N-RGO/TiO2 composites were used for photocatalytic experiments, and the photodegradation of methylene blue and fulvic acids was studied under simulated solar light. The results showed that the obtained N-RGO/TiO2 composites exhibited a much higher photocatalytic activity and stability compared with pure TiO2 and commercial P25. For the third photocatalysis degradation cycle, the N-RGO/TiO2 catalysts maintain 87% degradation of methylene blue within 1 hour. The RGO can improve the adsorption properties and photogenerated electrons transfer of composites, and N doped into composites can provides more active sites, and TiO2 with exposed facets can improve the quantum efficiency. Therefore, the photocatalytic performance of N-RGO/TiO2 composites has greatly improved.(4) The N-RGO/TiO2 composites also used for the adsorption of As(â…¢) and As(V). The results showed that the adsorption capacity of N-RGO/TiO2 composites for As(V) is higher than As(â…¢). Under the irradiation of ultraviolet light, the As(â…¢) could be quickly photo-oxidized to As(â…¤), and the As was adsorbed by N-RGO/TiO2 composites at the same time. In addition, the saturation adsorption capacity of N-RGO/TiO2 composites for As(â…¢) has improved under UV illumination.(5) Gas sensors were prepared by N-RGO/TiO2 composites, and the response of N-RGO/TiO2-based sensor were tested by different gases such as isopropanol, ethanol, acetone and so on. The results suggest that the sensor based on N-RGO/TiO2 exhibits better gas sensing properties than C-RGO/TiO2 composites, including response, response and recovery time, stability, selectivity and so on. Besides, the exposed facets of TiO2 can improve the gas detection limit, and make the conposites have response for isopropanol gas. |
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