Controllable Preparation Of Ceria-based Nanocomposite Particles And Their Properities

The development of CeO₂ particles with nanoscale have attracted great deals of attention from many researchers in automotive exhaust gas treatment,low temperature water-gas conversion reactions,and fuel cells because of their specific catalytic properties.However,due to the high surface energy of CeO₂ nanoparticles,the irreversible aggregation between the particles is very likely to occur during practical use,thus resulting in a significant decrease of its catalytic performance.Besides,the occurrence of aggregation also affect the repeated use of CeO₂ nanoparticles.In order to overcome the above shortcomings,the preparation of CeO₂-based nanocomposite particles has become a research hotspot.The existence of the carriers can not only effectively improve the catalytic stability of CeO₂ nanoparticles,but also improve the catalytic activity of CeO₂ nanoparticles under certain conditions.Based on this,this paper mainly focused on the simply preparation of CeO₂-based nanocomposite particles and the improvement of catalytic performance.The specific content includes the following three aspects:?1?Facile fabrication of raspberry-like polystyrene/ceria nanocomposite particles and their catalytic applicationHerein we present a facile approach to the attachment of ceria nanoparticles?CeO₂ NPs?onto polystyrene?PS?microspheres by a one-step process using the thermodynamic effects of the colloidal system.Specifically,in order to reduce the Gibbs free energy of the entire colloidal system,the hydrophilic ceria nanoparticles act as stabilizers and spontaneously deposit on the surface of the hydrophobic PS microspheres to obtain the PS/CeO₂ composite particles.Compared with the traditional method of preparing nano-cerium dioxide loaded on polymer microspheres,the preparation method proposed in this chapter has a prominent advantage,namely,avoiding complex surface functionalization or modification of the polymer microsphere carrier,which are usually indispensable in methods that have been reported.In addition,the results show that the size and number of CeO₂ nanoparticles deposited on the surface of PS microspheres can be regulated simply by changing the Ce?NO₃?₃·6H₂O concentration and the reaction temperature.Finally,using the obtained PS/CeO₂ nanocomposite as a catalyst,its catalytic effect on the degradation of methyl orange?MO?by hydrogen peroxide was investigated.It is noteworthy that these nanocomposite particles can catalyze the oxidative degradation of MO by hydrogen peroxide,and showed good stability during repeated use.?2?Preparation,characterization and catalytic properties of polystyrene/reduced graphene oxide@ceria?PS/RGO@CeO₂?nanocomposite particlesHerein we report a facile and straightforward two-step synthetic strategy to the fabrication of three-component polystyrene/reduced graphene oxide/ceria nanoparticles?PS/RGO@CeO₂?nanocomposite particles for the first time.As a functional material,when cooperate with CeO₂ nanoparticles the reduced graphene oxide?RGO?will increase the electronic conductivity and thus improve the catalytic activity of CeO₂.And a suitable support to form a ternary composite catalyst can also solve the problem of stacking of graphene during the use.Therefor,the PS/RGO@CeO₂ nanocomposite particles were prepared successfully by a simple method on the basis of PS/CeO₂.First,PS microspheres were prepared,and the GO can deposited on the surface of PS based on the hydrophobic interation and?electron interactions between PS microspheres and GO.After the addition of hydrated hydrazine,the PS/RGO composite particles were obtained.The PS/RGO@CeO₂nanocomposite particles were obtained by heating the PS/RGO dispersion with the Ce?NO₃?₃as precursor and HMT as mineralizer for a certain time.In the above preparation process,the CeO₂ particles stabilized by HMT can deposited on PS/RGO by electrostatic interaction.And the size and amount of the CeO₂ nanoparticles in the composite particles can be easily controlled by changing the amount of Ce?NO₃?₃ and the temperature of the reaction system.According to this principle,when AHA was used instead of HMT,the composite particles can also be successfully prepared.According to this principle,when HMT was replaced by AHA,composite particles can still be successfully prepared.When used for the catalysis of methylene blue?MB?dyes,the PS/RGO@CeO₂ nanocomposite particles showed enhanced photocatalytic activity compared with the PS/CeO₂ particles with similar CeO₂ particle size,and exhibited higher reused stability.?3?Fabrication of Pd@Ceria?Pd@CeO₂?hollow composite microspheres and their catalytic applicationIn this chapter,Pd nanoparticles were encapsulated in the CeO₂ hollow microspheres by a template sacrificial method.Pd@CeO₂ hollow composite microspheres were prepared as follows:First,PVP-stabilized PS microspheres were synthesized by the same method mentioned above.An appropriate amount of PS microsphere dispersion and palladium chloride were mixed and and heated for a certain period,with PVP as the reducing agent and stabilizer then the PS/Pd composite particles were fabricated,without adding additional reducing agent.Secondly,the PS/Pd@CeO₂ composite particles were obtained by mixed the pretreated PS/Pd composite particles with Ce?NO₃?₃ and HMT through heating treatment.Finally,PS microspheres were etched off with toluene to obtain Pd@CeO₂ hollow composite microspheres.In addition,PS/Pd composite particles with different particle sizes and loadings can be easily obtained by simply changing the amount of PS.Finally,by simply controlling the amount of Ce?NO₃?₃,the shell of CeO₂ with different thickness can be obtained,so the whole process is simple and controllable.The catalytic activity and stability of the obtained catalyst were studied by the photodegradattion of MB.The experiment results show that Pd can effectively improves the catalytic activity of CeO₂,while the structure of the internal encapsulation type is the another reason why the catalyst has good cycling stability.