| In recent years, with the rapid development of global economy and the excessive consumption of the fossil fuels, human beings are suffering from a severe energy crisis brought on by overexploitation, and the consumption of the fossil fuels also brought serious environmental pollution problems. Thus, environment pollution and energy crisis are considerably serious problems which need to be solved by human beings. Especially, based on the research results of photocatalytic field in1972, Fujishima and Honda in Tokyo University reported that the cell which is composed of TiO2semiconductor electrode and metal electrode can be used to split water into H2and O2under UV light irradiation. From then, semiconductor photocatalytic technology has been considered to be a kind of effective strategy to solve global environment problem and energy crisis. Semiconductor photocatalytic technology can exploit the solar energy to product hydrogen and decompose organic pollution, which has important implications for global new energy development and environment management.Currently, a wide range of broad band-gap semiconductor materials which generally possess d0electronic structure have been developed as photocatalysts, and the materials have poor utilization rate for solar energy due to the local property of d electrons. We choose Zn2SnO4as based mateial to study in the paper, which is attributed to its d0electronic structure. However, most of these materials due to its wide-band-gap are restricted in the practical application. The semiconductors only absorb UV light which occupies a fraction of the solar spectrum to limit its activity in visible light. Therefore, it is necessary to adopt an effective way to extend the light responsive range to achieve the visible light activity of the semiconductors. In this thesis, our work mainly focus on the construction of heterojunction between Zn2SnO4and BiOI and the surface coating of Zn2SnO4to expand the light absorption range, and achieve the photocatalytic activities of samples under visible light irradiation. The main research contents are listed as follow:Starting from chapter2, we successfully prepared the p-BiOI/n-Zn2SnO4photocatalysis by building the heterojunction method, and the heterojunctions possess excellent photocatalytic activities under the visible light irradiation. Firstly, BiOI/Zn2SnO4p-n heterojunction photocatalysts were prepared by anchoring n-type Zn2SnO4nanoparticles on p-type BiOI plates. The as-prepared catalysts exhibited excellent photocatalytic activities for the decomposition of methyl orange (MO) under visible light irradiation. The enhanced photocatalytic performance of BiOI/Zn2SnO4was not only attributed to the matched band potentials but also the interconnected heterojunction of BiOI and Zn2SnO4nanoparticles. Under visible light irradiation, the electrons in the conduction band of p-type BiOI would be excited into the conduction band due to the matched band potentials between Zn2SnO4and BiOI. Moreover, the internal electric field can accelerate the electron transfer and inhibit the recombination of photogenerated electron-hole pairs.In Chapter3, we mainly introduce that highly effective Zn2SnO4composite photocatalysis were sucessfully synthesized by a facile two-step hydrothermal method. Firstly, we choose the green glucose and as-prepared Zn2SnO4sample as the precursors to produce the Zn2SnO4composite photocatalysis. The photocatalytic activties of composites were evaluated by Rhodamine B degradation under visible light irradiation (λ≥420nm). The photocatalytic results showed that the pure Zn2SnO4exhibits a weak degradation efficiency, while Zn2SnO4composites have excellent the photodegradation efficiencies of Rhodamine B. The enhanced photocatalytic performance of the composites was mainly attributed to the existence of carbon on the surface of Zn2SnO4. The presence of carbon can not only enhance the visible-light absorption capacity but also inhibit the recombination ability of the photogenerated charge carriers of the composites. In addition, we produced two type Zn2SnO4semiconductors the by adding different zinc sources in the hydrothermal process. Compared to an ideal inverse spinel structure, the band edge of one of the samples has an markedly redshift due to the cation redistribution, which is contributed to the diversity of the cation distribution of Zn2SnO4. The work illuminates that the carbon coating method can enhance the photocatalytic activity of Zn2SnO4semiconductor.In chapter4, we summarize the conclusions and innovative points of this dissertation, and preview the further studies. |
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