Investigation On The Doping, Composite Modification And Photocatalytic Performance Of ZnO Nanomaterials

With the rapid development of industry,science and technology,various energy shortages and pollution problems are coming one after another.With the exhaustion of energy,air,soil and water pollution are becoming more and more serious and attracting more and more attention.The semiconductor photocatalysis technology can skillfully link the rational use of renewable resources-solar energy and environmental pollution control,using solar energy to irradiate semiconductor catalysts to achieve the purpose of degrading pollutants.ZnO has the characteristics of stable chemical properties and is not easily decomposed by heat,and it is widely studied because of its low price,non-toxicity and no introduction of secondary pollution.However,the photocatalytic efficiency of pure ZnO is not satisfactory,mainly due to its low quantum efficiency and large photogenerated electron-hole recombination rate;and the wide band gap so that it can only absorb the ultraviolet spectrum.In this paper,we intend to dope rare-earth elements into ZnO,and explore the effects of Gd and Ce doping and concentration on the structure,morphology,energy gap,photo-induced carrier recombination and photodegradation activity of ZnO.Further improve photocatalytic activity and broaden light absorption to a wider range.The effects of rare earth doping and composite graphene on the crystal structure,morphology,energy gap,photo-induced carrier recombination and photodegradation activity of ZnO were studied by XRD,SEM,TEM,UV-Vis,PL,Raman and other test methods And analyze its catalytic mechanism,the specific research content is as follows:In order to broaden the spectral absorption range and photodegradation activity of pure ZnO,Gd and Ce were selected as doping elements,and Gd-ZnO and Ce-ZnO photocatalysts were prepared by solvothermal method.Experiments confirmed that the doping of Gd and Ce ions will not affect the phase of ZnO itself,only a slight shift in the peak position of the diffraction peak.Among them,the doping of rare earth Gd ions changes the morphology of ZnO from rod to small sphere;and the doping of rare earth Ce ions slightly inhibits the growth of ZnO,making the rod shorter.Ultraviolet absorption spectrum shows that the light absorption capacity of doped Gd and Ce ZnO is obviously improved,and the light absorption range is expanded from ultraviolet to visible light.Rare earth ions have a unique 4f electron configuration,which can be used as a trap to capture photogenerated electrons,reduce photo-induced carrier recombination,and thus significantly enhance photodegradation activity.The results show that the doping of Gd and Ce has a significant effect on improving the photodegradation performance of ZnO,and the photodegradation activity is the best when the doping amount is 3% mol and 2% mol,respectively.The photocatalytic degradation rate of 3% mol Gd-ZnO reached 70.9%,and the photocatalytic degradation rate of 2% mol Ce-ZnO was 58.3%.In order to further enhance the photocatalytic activity of ZnO and increase its light absorption range,Ce-ZnO/RGO photocatalyst was obtained by compounding graphene on the basis of rare earth doped ZnO.The results show that Ce doping and composite graphene do not affect the phase structure of ZnO,and the diffraction peak is slightly shifted to a small angle.Raman spectroscopy and infrared spectroscopy showed that graphene oxide was successfully reduced during the growth of ZnO.The ultraviolet absorption spectrum shows that the Ce-ZnO/RGO catalyst material has significantly enhanced light absorption in the visible range.PL spectrum proves that doping Ce and composite graphene significantly reduces the recombination rate of photogenerated carriers.Rhodamine B degradation experiments show that Ce-ZnO/RGO has excellent photodegradation activity,and the degradation rate is as high as 98.6%.Analysis of the special configuration of rare earth Ce ions can be used as a trap to capture photogenerated carriers.Graphene’s excellent electron transport capability accelerates the transport and transfer of photogenerated carriers.The combination of both significantly enhances the photocatalytic activity of ZnO.