| TiO2and ZnO are the most commonly used photocatalysts. However, it is a pity that both of them can only be activated by ultraviolet light or near-ultraviolet light because of their broad band gap (3.0-3.2eV), hence only less than5%solar energy can be utilized. Therefore, finding a kind of photocatalysts which can make full use of solar energy and have high photocatalytic activity have been the main research direction. The majority of irradiation (about43%) of sunlight lies in the visible range, and only photocatalysts with corresponding band gap can make full use of the solar energy. Cuprous oxide (Cu2O) has a direct band gap of about2.17eV, can be inspired by the400-800nm visible-light and product electron hole pair under the irradiation of sunlight,which makes it a promising material for solar energy conversion and visible photocatalytic degradation of pollutants. The single phase photocatalysts exhibit very low quantum efficiency because of the easy recombination between photo-electrons and holes, the development and utilization of Cu2O is greatly limited. In order to improve the photocatalytic ability of Cu2O, Cu/Cu2O NCs and different morphology of Cu2O nanocrystals were synthesized. This thesis consists of three following aspects:1. we synthesized Cu/Cu2O NCs by the simple one-pot solution-phase solvent route. In the experiment, we employed Cu(NO3)2·3H2O as the raw material, PVP as the protective agent and EG as the solvent and reducing agent. The phase compositions and morphology of Cu/Cu2O NCs are controlled by adjusting the reaction time. The photocatalytic mechanism of Cu/Cu2O NCs are also investigated. It can be concluded that the content of Cu in the final samples could be tuned by controlling the reaction time at180℃. Otherwise the content of Cu in the Cu/Cu2O NCs plays an important role on the photo-catalytic activity. At the first20min of irradiation, the photodegradation efficiency of MO solution in the presence of Cu/Cu2O NCs with low content of Cu (S2-S4:2.1-9.2%) reach up to99.78%,99.77%,98.39%, respectively. Compared with S2-S4, under the same conditions, the maximum degradation efficiency of MO with pure Cu2O (S1),Cu/Cu2O NCs with a high Cu content (S5, S6:68%and96%) are only45.88%,73.03%and51.22%, respectively, even though after visible light irradiation for50min, only the degradation efficiency of85.30%,94.67%and69.33%. Besides, the photostability of Cu/Cu2O NCs was studied by recycles.2. we synthesized Cu2O nanocrystals by the simple one-pot solution-phase solvent route. In the experiment, we employed Cu(NO3)2·3H2O as the raw material, PVP as the protective agent and surfactant, EG as the solvent and reducing agent. The morphology of Cu2O nanocrystals was influenced by the PEG concentrations and EG concentrations. The photocatalytic mechanism of Cu2O nanocrystals were also investigated. When the EG concentrations was the same, PVP kinetically controlled the growth rates of different crystalline faces of Cu2O by interacting with these faces through adsorption and desorption. when the radio of PVP/Cu(NO3)2·3H2O was0.022, it can be clearly seen that the surface of the spheres is covered with Cu2O crystal thorn. As the molar radio of PVP/Cu(NO3)2·3H2O increases from0.022to0.067, the surface of the spheres is covered with Cu2O crystal corner. Increasing the radio of PVP/Cu(NO3)2·3H2O from0.067to0.111, the surface of the spheres is made from an assembly of smaller spherical particles. When the composition of EG increases from50ml to90ml (S3), and other experimental conditions are kept the same, the morphology of the surface of the spheres change from Cu2O crystal thorn into spherical particles. When the reaction time increases from20min to30min (S3), and other experimental conditions are kept the same, the morphology of the obtained samples change from "open mouth" or broken hemispheres into perfect spheres without broken. At the first10min of irradiation, the photodegradation efficiency of MO solution in the presence of Cu2O NCs (S1-S5) reach up to97.69%,10.36%,42.44%,89.93%and99.67%respectively, the surface of the spheres covered with Cu2O crystal thorn show the optimal photocatalytic activity.3. we synthesized Cu2O nanocrystals by the simple one-pot solution-phase solvent route. In the experiment, we employed Cu(NO3)2·3H2O as the raw material, EG as the solvent and reducing agent. The morphology of Cu2O nanocrystals are controlled by adding PVP、 hydrazine hydrate or glucose. The photocatalytic mechanism of Cu2O nanocrystals are also investigated. At the first10min of irradiation, the photodegradation efficiency of MO solution in the presence of Cu2O NCs (S1-S3) reach up to97.50%,61.61%and98.76%respectively.Due to the high temperature adverse to mass production, herein, we put forward a convenient solution-phase method for the synthesis of Cu2O truncated octahedral and octahedral crystals. The Cu2O crystals were selectively synthesized without surfactant and organic solvent at room temperature, with Cu(NO3)2·3H2O and NaOH as starting reactants, and hydrazine hydrate or glucose as the reducer.At the30min of irradiation, the photodegradation efficiency of MO solution in the presence of Cu2O NCs (S4, S5)are22.36%and11.30%.The Cu/Cu2O CNs and different morphology of Cu2O nanocrystals are synthesized by the simple one-pot route.This method, simple and effective, may be helpful for the study on controlled synthesis of other materials. The high photocatalytic activity of Cu/Cu2O CNs and different morphology of Cu2O nanocrystals suggests they are promising materials for processing of waste water. |
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