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Modification Of ZnS1-x-0.5yOx(OH)y-ZnO Solid Solution With NiS And Its Photocatalytic Performance For Hydrogen Evolution From Seawater Under Visible Light

Posted on:2014-11-13Degree:MasterType:Thesis
Country:ChinaCandidate:S Y LinFull Text:PDF
GTID:2251330401972268Subject:Inorganic Chemistry
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In this thesis, we modified the basic Zincoxysulfide (ZnS1-x-0.5yOx(OH)y-ZnO) solid solutions by doping Ni2+and loading NiS, and investigated the photocatalytic hydrogen evulution from seawater over the modified ZnS1-x-0.5yOx(OH)y-ZnO using Na2S and Na2SO3as mixed electron donors. The possible mechanisms were discussed. This work mainly includes three parts.In the first part,we studied the effects of Ni2+doping on photocatalytic hydrogen evolution over ZnS1-x-0.5yOx(OH)y-ZnO phtotcatalysts, and contrasted its different photocatalytic performance between in pure water and in seawater.The catalysts were characterized by X-ray diffraction(XRD),specific surface area (BET),transmission electron microscopy(TEM),UV-Vis absorption spectroscope(UV-Vis DRS), X-ray photoelectron spectroscope(XPS).The results showed that doping Ni2+improve the photocatalytic performance of the catalyst. Moreover, when the doping content of Ni2+reached or greater than0.75wt%, activity of the catalyst in seawater system was higher than that in pure water system.Mechanism research shows that since Ni2+doping content is low, the doping ions lies at the suface lattice sites,and Ni2+exitst in the form of Ni(OH)2. However, in the system of Na2S and Na2SO3as mixed electron donors, Ni2+exists in the form of NiS.In the second part, NiS was loaded on ZnS1-x-0.5yOx(OH)y-ZnO photocatalyst by two methods (impregnating the photocatalyst in a NiS sol and depositing NiS on it via a precipitation reaction). The activity of the NiS-modified photocatalyst for hydrogen evolution from pure water and seawater was investigated using mixed electron donors (Na2S-Na2SO3). The activity (in pure water-electron donor solution) is dependant of the modification method and loading content of NiS. When Na2S-Na2SO3was added into seawater, a mixture precipitate (Mg(OH)2and CaSO3) produced. The precipitate is detrimental to the photocatalytic hydrogen evolution over unmodified ZnS1-x-0.5yOx(OH)y-ZnO. However, for the NiS-modified photocatalyst, the detrimental effect decreases notably. Interestingly, the activity of the modified photocatalyst in seawater-electron donor solution (with the precipitate) is higher than that in the pure water-electron-donor solution (without the precipitate). The possible mechanism was discussed.In the third part, three kinds of NiS were prepared by homogeneous precipitation-calcination, hydrothermal and solvothermal method, respectively. The results indicated that their crystalline phases were hexagonal phase, rhombohedral phase and mixed crystallite phase.Through ultrasonic dispersion method mexed the ZnS1-x-0.5yOx(OH)y-ZnO and three kinds of NiS, the activity of the NiS-modified photocatalyst for hydrogen evolution from pure water and seawater was investigated using Na2S-Na2SO3as mixed electron donors.The results show that loading three kinds of NiS can enhanced the photocatalytic performance of ZnS1-x-0.5yOx(OH)y-ZnO,and the activity order is mixed crystallite phase> rhombohedral phase> hexagonal phase. The photocatalytic hydrogen evolution over unmodified ZnS1-x-0.5yOx(OH)y-ZnO is lower than that of from pure water,however, while for the NiS-modified photocatalyst, the activity of the modified photocatalyst in seawater-electron donor solution is higher than that in the pure water-electron-donor solution. The results further confirm our previous conclusion.
Keywords/Search Tags:ZnS1-x-0.5yOx(OH)y-ZnO, Ni2+ doping, NiS loading, seawater, photocatalysis, Hydrogen evolution
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