| The industrial revolution had provided enormous material wealth to people. At the same time, high-speed development of modern industry induces exploitation and utilization of fuel energy in very large scale, which results in severe consequence that source of energy such as coal, oil and nature gas are almost dried up; Greenhouse effect is much more apparent and the environment pollution is startling. These environment and energy problems have seriously threatened people’s existence and development on the earth. Therefore, some steps are having been taken to cope with energy and environment risks positively. The government department of different countries, the scientific community and enterprises are making their efforts to seek for new energy which can substitute for fossil fuel energy and have safe and pollution-free, clean, economic and sustainable advantages in order to fundamentally solve the energy and environment problems. Serving as the most abundant energy in nature, solar energy is the most ideal substitute energy source at present since the outstanding character of no pollution and reproducibility. Compared with coal, oil and nuclear energy, solar energy has distinctive advantages:firstly, it couldn’t pollute environment; secondly, no restriction in region and resource, as well as safe and convenient; at last thermonuclear reaction of the sun can sustain6×1010years according to the its mass loss rate, therefore, solar energy is inexhaustible and reproducible clean energy to human beings. Among numerous new technologies to exploit solar energy, photocatalytic technology based on semiconductor is the most potential and environment friendly technology since its own unparalleled advantages compared with other technologies, such as low exploitation cost, less energy consumption and no secondary pollution.Two kinds of NaNbO3samples were prepared, which have different morphology by altering the content of NaCO3in reactants using topochemical microcrystal conversion method. The flocculent NaNbO3is successfully prepared firstly. Meanwhile, two kinds of platelike NaNbO3were also prepared by using one-step and two-step molten salt methods, moreover they were sensitized with carbon nitrogen compounds which have strong redox ability, As a result, the catalytic performance of platelike NaNbO3catalysts is effectively improved. At last, We also do systematically research using simple thermal decomposition method for more insight about the Ag content (Ag wt%>3%) influence on the structure and catalytic character of g-C3N4.The main works are as follows:Firstly, the influence of preparation temperature and soaking time on the phase structure and surface morphology of Bi2.5Na3.5Nb5O18were studied; next, platelike and flocculent NaNbO3were successfully prepared by changing the content of Na2CO3in reactants. The flocculent NaNbO3is reported firstly by this article according to literatures we have known. The photocatalytic performance of samples was evaluated through degradation of MO. The flocculent NaNbO3has stronger catalytic ability compared with platelike NaNbO3, and the phenomenon that two kinds of NaNbO3samples show different photocatalytic activities has been discussed.Secondly, two kinds of platelike NaNbO3were prepared by using one-step and two-step molten salt methods. The phase, structure, surface morphologies and optical absorption properties of samples systematically were charactered through XRD, FT-IR, SEM, Uv-Vis spectroscopy, respectively. Moreover, comparative research about their diffferent catalytic performances were performed. Two challenging obstacles for the application of pure phase NaNbO3in the field of photocatalysis are low oxidize ability and high photo-generated carriers recombination. Luckly, g-C3N4is a new kind of efficient photocatalyst springing up in recent years which has stronger oxidation and reduction ability. The new kind of photocatalyst has better performance in degradation of organics and water splitting, also. So a little g-C3N4was used to sensitize two kinds of platelike NaNbO3. And the mechanism for the difference of catalytic performance resulted from two kinds of composite catalysts were also discussed.At last, g-C3N4photocatalyst was prepared by heating urea at600℃for half an hour. When the mass ratio of AgNO3and g-C3N4was separately0,0.05,0.1,0.2,0.3, Ag/g-C3N4composite photocatalysts were successfully prepared by heating the mixture of AgNO3and g-C3N4reactants. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) were used to analyze the phase and structure of the pyrolysis products. The light absorption range and fluorescence properties of the samples can be tested through UV-Vis spectroscopy and Photoluminescence analysis (PL). The photocatalytic activities of the samples under visible light irradiation (λ≥420nm) were evaluated by monitoring oxidation of RhB evolution. The results showed that high silver deposit quantity could impact the structure of carbon nitrogen compounds, while the optimal content of metal Ag was determined to be3%. According to analysis, the enhanced photocatalytic performance could be mainly attributed to the synergic effect between Ag and g-C3N4, which inhibited photo-generated carriers recombination. |
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