| ZnO nanomaterial has a broad application prospect and unique advantage in the useof many fields especially in the field of photo-degradation of organic pollutant due to itsspecial band structure and good chemical stability. However, the wide band gap and thequick recombination of electron-hole pairs seriously hindered its applications in the fieldof photocatalysis. Recent years, much effort had been made to facilitate ZnO to utilizevisible light and increase the electron-hole pair separation efficiency, such as depositingnoble metals on ZnO surface, doping with metallic or non-metallic element into ZnO.Based on this, we synthesized Ag deposited ZnO nanocatalysts with two differentmethods, and then, N doped ZnO/Ag nanacatalysts were successfully synthesized withNH3as the nitrogen source. The synthesis processes of ZnO/Ag, N-doped ZnO/Ag wereoptimized respectively. The photocatalytic activity and the impact of Ag content ofZnO/Ag and N-doped ZnO/Ag nanocatalysts under simulated sunlight were studied anddiscussed. The main research contents were as follows:(1) ZnO/Ag nanocatalysts were successfully synthesized by complex precipitationmethod, in which Zn(NO3)2·6H2O、AgNO3as raw material, NaOH as the precipitatingagent，C6H12O6as the reductant agent. The synthesis processes were optimized with thephotodegradation rate of methyl orange (MO) as indicator. The microstructures,morphologies, Ag content and absorption spectroscopy of products were characterized byX-ray diffraction (XRD), Field emission scanning electron microscopy (SEM),transmission electron microscopy (TEM), inductively coupled plasma optical emissionspectrometry (ICP-OES) and ultraviolet-visible spectrophotometer (UV-vis). Resultsindicated that when the reaction conditions were that the mixture of Zn(NO3)2and AgNO3was dropped into the mixture of NaOH and C6H12O6at60℃, the molar ratio of Zn2+andOH-was1:8, the products had best photocatalytic activities. And under the irradiation of800w Xe lamp for120min, the photo degradation rate of MO was91%. The ZnOnanorods had a Wurtzite structure, their average rod diameter was about80nm while thelength of them was about500nm. The Ag nanoparticles had a face centered cubic structure, and the average diameter was about20nm.(2) ZnO/Ag nanocatalysts were successfully synthesized by sol-gel method, in whichZn(NO3)2·6H2O、AgNO3as the raw material, citric acid as the reductant agent, glycol asthe coupling agent. The synthesis processes were optimized with the photodegradationrate of methyl orange (MO) as the indicator. The microstructures, morphologies, Agcontent and absorption spectroscopy of products were characterized by X-ray diffraction(XRD), Transmission electron microscopy (TEM), Inductively coupled plasma opticalemission spectrometry (ICP-OES) and Ultraviolet-visible spectrophotometer (UV-vis).Results indicated that when the calcination temperature of Precursor was500℃, thecalcination time was120min, the products had the best photocatalytic activities. Andunder the irradiation of800w Xe-lamp for120min, the photo degradation rate of MOwas100%. The ZnO and Ag were all in the shape of particles.(3) N-doped ZnO/Ag nanocatalysts were synthesized by atmosphere nitridingmethod with NH3as the nitrogen source. The synthesis processes were optimized with thephotodegradation rate of methyl orange (MO) as the indicator, and the optimizedcondition was that the nitriding temperature was600℃, the nitriding time was120min.N-doping did not change the crystal structure and morphology of ZnO/Ag nanocatalysts,but their simulated sunlight photocatalytic activities were significantly improved.(4) Different Ag contents of ZnO/Ag nanocatalysts and N-doped ZnO/Agnanocatalysts were synthesized by complex precipitation method and atmospherenitriding method under the optimized condition above, and the impact of Ag content tothe photocatalytic activities were studied with the photodegradation rate of MO as theindicator. The N-doping content was also analysed by Elemental Analyzer. Resultsshowed that the ZnO/Ag nanocatalysts with5%Ag content exhibit best photocatalyticactivities, the N-doped ZnO/Ag with3%Ag content had a maximum N content of3.7wt%, and the N-doped ZnO/Ag with the Ag content of8%, N content of2.1wt%, hadthe best photocatalytic activities. |
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