| Nano-particles rare earth metal oxides have important technical significance in various chemical and material science fields of catalysis,energy storage,electron and other.As is known to us all,cerium is an important rare earth element with important physical and chemical properties.CeO2 has a relatively small band gap(3.19 eV),which has considerable light on the degradation of dye catalysis.CeO2 has the advantages of photocatalysis with high efficiency,low cost,high stability,and the environmental friendly.In recent years,CeO2 nanoparticles have been widely concernedin polishing material,catalyst and oxygen sensors and irradiation,and other fields.The main results in this paper are as follows.1.The precursor CeOHCO3 was synthesized by the hydrothermal method,using cerium nitrate(Ce(NO3)3·6H2O)as the source of cerium,urea(CO(NH2)2)as precipitating agentand second hydration trisodium citrate(Na3C6H5O7·2H2O)as surfactant,changing the reaction time.Cauliflower-like CeO2was successfully obtained by thermal decomposition the precursor CeOHCO3.The influence ofthe reaction time to the morphology,crystal structure and magnetic properties has been studied.The test results of X-ray photoelectron spectroscopy(XPS)show that the Ce4+and Ce3+ ions coexist in the surface of the particles.Through the analysis,we think that the ferromagnetic at room temperaturerelated to the existence of Ce3+ on the surface.2.CeOHCO3 precursors were successfully synthesized by a one-step hydrothermal method,using cerium nitrate(Ce(NO3)3·6H2O)as the source of cerium,polyvinylpyrrolidone and nitric acid and urea(CO(NH2)2)as the surfactant and precipitant.Loose cerium oxide empty core ball was obtained by thermal decomposition of CeOHCO3 precursors.X-ray diffraction(XRD)shows that with the extension of the reaction time,the sample gradually into CeO2.When the reaction time is 60 h,only CeO2 were detected,with a cubic fluorite structure.The photocatalytic performance of the ceria was investigated by the photodegradation of methyl orange under Uv-vis irradiation at room temperature.It has been proved that Ce3+ ions,oxygen vacancies and high specific surface area can makeloosen CeO2 hollow core balls have the good ferromagnetismand excellent photocatalytic performance.3.Spindle-like ceria particles were synthesized by hydrothermal method,using nitrate cerium(Ce(NO3)3·6H2O)as the source of cerium,urea(CO(NH2)2)as the precipitant.Spindle-like ceriahave been characterized by the X-ray diffraction(XRD),thermogravimetric(TG),scanning electron microscope(SEM),photoluminescence(PL),uv-vis spectra and Raman spectra.XRD confirmed the cubic fluorite structure and calculated the grain size of ceria.The reaction process and chemical mechanism was analyzed by thermogravimetric analysis and differential thermal analysis,The results show that cerium oxide powder synthesized at 600 ? had a higher crystallization.The reaction time and concentration have been systematically studied.The results showed that the reaction time,reaction concentration werethe key parameter to control the final morphology.Hybrid oxidation state of samples(Ce4+,Ce3+)and the concentration calculation were tested and calculated using X-ray photoelectron spectroscopy(XPS)and Raman spectroscopy(Raman).The oxygen vacancy and Ce3+ ions were proved to exist in the grain surface and grain boundary.The presence of emission peak and visible photoluminescence peakcan be attributed to the oxygen vacancy.the existence ofCe3+ ionsand oxygen vacancy will lead to the formation of some local band gap state,which may be the cause of the band gap redshift in spindle CeO2 samples.4.CeOHCO3 precursorswere synthesized by a no template step hydrothermal method,using cerium nitrate(Ce(NO3)3·6H2O)as the source of cerium,polyethylene glycol(PEG)as the surfactant,urea(CO(NH2)2)as the precipitant,controlling the temperature,concentration and the time.CeO2 nanoparticles with core-shell structure were successfully obtained by through thermal decomposition.The structure,morphology and optical propertiesof cerium oxide nanospheres were characterized using X-ray diffraction(XRD),thermogravimetric(tg),Fourier transform infrared spectroscopy,X-ray diffraction(XRD)and energy spectrum,SAED,scanning electron microscope(SEM)and transmission electron microscope(TEM),BET and uv-vis diffuse reflection spectroscopy,Raman spectroscopy analysis.The concentration of Ce4+,Ce3+ and oxygen vacancies was calculated by XPS.The degradation of methyl orange rate are 93.49%,95.67%and 93.49%respectively within 160 min and the photodegradation rate of methyl orange were 0.01693 min-1,0.01782 min-1,and 0.02375 min-1 under ultraviolet radiation.The process of photocatalytic oxidation degradationmainlygave the credit to a large number of active substances,such as h+?surface ultra oxygen anion·O2-and ·OH radicals.The analysis result was that the core-shell structure,grain size,the transformation of Ce4+ and the Ce3+,and high surface area were of great significanceon its catalytic activity. |
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