Synthesis And Catalytic Properties Of Ceria And Its Noble Metal Loaded Catalysts

Rare earth micro/nanostructured catalytic materials show many special properties which are different from other materials owing to their unique quantum size effect and macroscopic quantum tunneling effect.Rare earth oxides,precious metals and their composite materials are widely used as the catalyst in fuel cells,oxygen sensors,three-way catalyst,advanced structural ceramics,petrochemical and other fields.In this paper,CeO₂ and its supported noble metal catalysts were studied,multi-shelled CeO₂,multi-shelled Au/CeO₂ and AuPd/CeO₂ catalysts and CeO₂ nano particles have been successfully synthesized by employing solvothermal and microwave-assisted heating method.The as-prepared products were characterized by different measurement technologies.The formation mechanism and properties of the products were briefly discussed and summarized.It may provide method and experiment instruction for the synthesis of other coordination polymers and rare earth oxide.The main content of this thesis is as following:?1?Multi-shelled ceria hollow spheres with tunable shell number,thickness and their superior catalytic activity.Herein,solvothermal and simple template-free approach is adopted to fabricate multi-shelled Ce O₂ hollow nanospheres with porous shells,other multi-shelled structure of rare earth oxides were also prepared by similar procedure.The approach involves a mixed-solvothermal synthesis of the Ce-based coordination polymer nanospheres?Ce-CPs?and followed by a simple calcination treatment in air,nitrogen and argon.Through the control of the synthesis conditions,it was found that the multi-shelled ceria hollow spheres with tunable shell number,thickness can be synthesized by calcination in air atmosphere The multi-shelled Ce O₂ hollow nanospheres present excellent photocatalytic degradation of Rh B.More importantly,the as-synthesized multi-shelled Ce O₂ hollow nanospheres with porous shells and a high surface area may endue them with wide range of important potential applications in adsorption of pollutants in wastewater and gas sensing.?2?CeO₂ loaded with Au and AuPd: fabrication and their catalytic performanceBased on the above synthesis of CeO₂ with multi-shelled structure,the supported catalyst Au/CeO₂ and AuPd/CeO₂ were prepared by aqueous solution impregnation method and use the multi-shelled CeO₂ as carriers,The catalytic properties of multi-shelled CeO₂ and commercial Ce O₂ were compared.The results show that the catalytic activity of Au/Ce O₂ and Au Pd/Ce O₂ are better than multi-shelled CeO₂,and they are superior to the commercial Ce O₂,the former three catalysts were sorted Au Pd/Ce O₂>Au/Ce O₂> Ce O₂,according to the catalytic effect.?3?Fast microwave synthesis of multi-shelled CeO₂ nanospheresBased on the successful solvothermal synthesis CeO₂ with multi-shelled structure,the method of synthesizing multi-shelled CeO₂ by simple and rapid microwave-assisted method was studied.Ce-based coordination polymer nanospheres have been successfully synthesized employing pyridine-2,5-dicarboxylate acid?2,5-H₂PDC?as ligand by a microwave route and followed by a simple calcination treatment in air.During the reaction,the morphologies of products were varied by controlling the reaction parameters?reaction time,solvent composition?.Furthermore,the properties of the products prepared by microwave method and mixed solvent thermal method were compared.The results show that the microwave assisted preparation of CeO₂ with multi-shelled structure can improve the UV absorption performance.?4?Microwave assisted synthesis of ceria nanoparticlesCeria nanoparticles were successfully prepared employing an modified home microwave oven?power continuously adjustable?with water as solvent and organic amine as the base source?triethylenetetramine,tetraethylenepentamine,diethanolamine and triethanolamine?,without the using of any surfactant.The ceria nanoparticles are with diameters of 3-5 nm and BET surface of 189.00 m²g^-1.Furthermore,it is homogenous and well dispersed.The organic amine as the alkali source can not only play the role of alkali,but also play the role of surfactant,reduce the particle size of CeO₂,and the product is not easy to reunite.