Preparation Of Ce O₂-based Composites And Their Catalytic Applications

CeO₂ is one of the important rare earth materials with abundant reserves and is widely used in heterogeneous catalytic reactions such as three-way catalysis and selective oxidation.In practical applications,pure Ce O₂ catalytic performance is often difficult to meet the actual needs,so modification of Ce O₂ is one of the important means to improve its catalytic activity.?1?Influence of CeO₂ morphologies:Five different morphologies of Ce O₂ were synthesized,including nanoparticles?NP?,nanorods?NR?,nanocubes?NC?,octahedron?NO?,and large flakes?NF?and their respective catalytic activities were tested by three different methods.The order of catalytic activity of Ce O₂ with different morphology at low temperature was NF>NP>NR>NC?NO.Ce O₂ samples with different morphologies have different active crystal planes,different numbers of oxygen vacancies on the surface,and different Ce³⁺content,which lead to their different catalytic activities.XRD,IR,nitrogen adsorption,TEM and XPS were used to characterize the synthesized Ce O₂ with five different morphologies,and a reasonable explanation was proposed to explain their activity differences.NP and NF surfaces had higher Ce³⁺%?23%and 31.7%,respectively?,which was conducive to the improvement of catalytic performance.The ratio of OH*/CO₃^2-on NP and NF surfaces was only 1.9%and 4.7%,while the ratio of OH*/CO₃^2-on other samples was 10.5%-16.6%.This may block some Ce³⁺on the surface,resulting in poor catalytic performance of NR,NC and NO.?2?CeO₂@BiOI composites and their application for Cr???degradation:Ce O₂ and Bi OI were combined to prepare Ce O₂@Bi OI composites,and their catalytic performance was examined by photocatalytic degradation of Cr???.The effects of the composite ratio of Ce O₂ and Bi OI on the properties of the composite were first investigated.The results showed that the Ce O₂@Bi OI composite had the best catalytic performance when Ce O₂:Bi OI=1:2?molar ratio?.Based on this,the effects of different Ce O₂ morphologies on the catalytic performance of Ce O₂@Bi OI were explored.The catalytic performance of Ce O₂@Bi OI composites prepared from nanoparticle Ce O₂-NP and Bi OI was the best.Finally,the effects of different Bi OI morphologies on the catalytic performance of Ce O₂@Bi OI composites were explored.The results showed that the Ce O₂@Bi OI composite formed from the sheet-shaped Bi OI and nanoparticle Ce O₂-NP at a molar ratio of 2:1 had the best removal effect for Cr???.?3?CeO₂/MoS₂ composites and their application in imine catalytic synthesis:Ce O₂?NP?was loaded on the surface of Mo S₂ by a simple precipitation method to prepare Ce O₂/Mo S₂composite material,and further used for the catalytic synthesis of imine.First,the effect of Ce O₂ loading ratio on the performance of Ce O₂/Mo S₂ composites were explored.When the molar ratio of Ce O₂ to Mo S₂ was 2:1,Ce O₂/Mo S₂ exhibited a better catalytic activity in imine synthesis.Further research showed that the morphology of Mo S₂ in Ce O₂/Mo S₂ can influence their catalytic performance for imine synthesis.Besides,the morphology of Mo S₂can also affect the composites'catalytic performance.Mo S₂-Flake had a larger specific surface area than the other two morphologies?Mo S₂-spherical and Mo S₂-plate?.In addition,Mo S₂-Flake had a uniform size and good dispersibility,which was more conducive to the loading of nanocrystalline Ce O₂.The binding between Mo S₂-Flake and Ce O₂ was stronger compared to other samples,so the conversion between Ce³⁺and Ce⁴⁺was faster,which resulted in more O*being produced,and it was beneficial for the synthesis of imine.