Ag nanoparitcles were prepared via Ultrasound-assisted Membrane Reaction(UAMR)method.The key issue of the method is to control precisely the injection speed of the reactants by pulseless pump to make the nanoparticles...Ag nanoparitcles were prepared via Ultrasound-assisted Membrane Reaction(UAMR)method.The key issue of the method is to control precisely the injection speed of the reactants by pulseless pump to make the nanoparticles of Ag with small size and narrow size distribution.The size and morphology of silver nanoparticles were characterized with Transmission Electron Microscope(TEM)and UV-Vis spectrum.The experiment results show that the size of Ag nanoparticles prepared via UAMR method was smaller than that via Ultrasound-assisted Dropping Reaction(UADR)method.The size of 80% Ag nanoparticles prepared via UAMR was ranged from 3 nm to 5 nm with the mean particle size 4.7 nm and considerable narrow size distribution.The Ag hydrosol fabricated via UAMR method was very stable at room temperature,even within three months.展开更多
Pd/CeO2 catalysts with flower-like morphology were fabricated via an ultrasonic-assisted membrane reduction （UAMR） and hydrothermal methods. The catalysts were physically characterized and evaluated for three-way ca...Pd/CeO2 catalysts with flower-like morphology were fabricated via an ultrasonic-assisted membrane reduction （UAMR） and hydrothermal methods. The catalysts were physically characterized and evaluated for three-way catalytic activities versus tradi- tional Pd/CeO2 catalysts. Flower-like Pd/CeO2 catalysts exhibited a higher catalytic performance and better thermal stability than the Pd/CeO2 prepared by conventional impregnation. The flower-like Pd/CeO2 catalysts were constructed from 20-50 nm thick nanosheet petals. These petals were in turn constructed from 10 nm CeO2 nanoparticles that self-assembled into the flower-like morphology re- sulting in abundant pores in all directions. The Pd nanoparticles were anchored and dispersed on both the interior and surface of the pores and had minimal sintering. When these catalysts were aged, the structure and morphology of the catalysts remained unchanged with important industrial implications for this new type of material including improved catalytic performance and high thermal stabil- ity. Regardless of the Pd loading, both the fresh and aged Pd/CeO2 catalysts prepared by the UAMR-hydrothermal method exhibited better performance than the corresponding samples prepared by conventional impregnation means.展开更多
A novel Ultrasonic Assisted Membrane Reduction （UAMR）-hydrothermal method was used to prepare flower-like Pt/CeO2 catalysts. The texture, physical/chemical properties, and reducibility of the flower-like Pt/CeO2 cat...A novel Ultrasonic Assisted Membrane Reduction （UAMR）-hydrothermal method was used to prepare flower-like Pt/CeO2 catalysts. The texture, physical/chemical properties, and reducibility of the flower-like Pt/CeO2 catalysts were characterized by X-Ray Diffraction （XRD）, Scanning Electron Microscope （SEM）, Transmission Electron Microscope （TEM）, N2 adsorption, and hydrogen temperature programmed reduction （HE-TPR） techniques. The catalytic performance of the catalysts for treating automobile emission was studied relative to samples prepared by the conventional wetness impregnation method. The Pt/CeO2 catalysts fabricated by this novel method showed high specific surface area and metal dispersion, excellent three-way catalytic activity, and good thermal stability. The strong interaction between the Pt nanoparticles and CeO2 improved the thermal stability. The Ce4＋ ions were incorporated into the surfactant chains and the Pt nanoparticles were stabilized through an exchange reaction of the surface hydroxyl groups. The SEM results demonstrated that the Pt/CeO2 catalysts had a typical three-dimensional （3D） hierarchical porous struc- ture, which was favorable for surface reaction and enhanced the exposure degree of the Pt nanoparticles. In brief, the flower-like Pt/CeO2 catalysts prepared by UAMR-hydrothermal method exhibited a higher Pt metal dispersion, smaller particle size, better three-way catalytic activity, and improved thermal stability versus conven- tional materials.展开更多
文摘Ag nanoparitcles were prepared via Ultrasound-assisted Membrane Reaction(UAMR)method.The key issue of the method is to control precisely the injection speed of the reactants by pulseless pump to make the nanoparticles of Ag with small size and narrow size distribution.The size and morphology of silver nanoparticles were characterized with Transmission Electron Microscope(TEM)and UV-Vis spectrum.The experiment results show that the size of Ag nanoparticles prepared via UAMR method was smaller than that via Ultrasound-assisted Dropping Reaction(UADR)method.The size of 80% Ag nanoparticles prepared via UAMR was ranged from 3 nm to 5 nm with the mean particle size 4.7 nm and considerable narrow size distribution.The Ag hydrosol fabricated via UAMR method was very stable at room temperature,even within three months.
基金Project supported by National Natural Science Foundation of China (20877006, 20833011)Beijing Municipal Natural Science Foundation (2101002)+2 种基金the Funding Project for Academic Human Resources Development in Institutions of Higher Learning under the Jurisdiction of Beijing Municipality (PHR201107104, PHR200907105)National High Technology Research and Development Program (2011AA03A406)National Industrial Project of New Rare Earth Materials
文摘Pd/CeO2 catalysts with flower-like morphology were fabricated via an ultrasonic-assisted membrane reduction （UAMR） and hydrothermal methods. The catalysts were physically characterized and evaluated for three-way catalytic activities versus tradi- tional Pd/CeO2 catalysts. Flower-like Pd/CeO2 catalysts exhibited a higher catalytic performance and better thermal stability than the Pd/CeO2 prepared by conventional impregnation. The flower-like Pd/CeO2 catalysts were constructed from 20-50 nm thick nanosheet petals. These petals were in turn constructed from 10 nm CeO2 nanoparticles that self-assembled into the flower-like morphology re- sulting in abundant pores in all directions. The Pd nanoparticles were anchored and dispersed on both the interior and surface of the pores and had minimal sintering. When these catalysts were aged, the structure and morphology of the catalysts remained unchanged with important industrial implications for this new type of material including improved catalytic performance and high thermal stabil- ity. Regardless of the Pd loading, both the fresh and aged Pd/CeO2 catalysts prepared by the UAMR-hydrothermal method exhibited better performance than the corresponding samples prepared by conventional impregnation means.
基金The authors are grateful for the National Natural Science Foundation of China （Grant Nos. 20877006 and 20833011）, National Industrial Project of Rare Earth and Rare Metal New Materials and the Project funding for Academic Human Resources Development in Institutions of Higher Learning under the Jurisdiction of Beijing Municipality （Nos. PHR201107104 and PHR200907105）. We also thank Mining and Metallurgy Research Institute of Beijing for the TEM access.
文摘A novel Ultrasonic Assisted Membrane Reduction （UAMR）-hydrothermal method was used to prepare flower-like Pt/CeO2 catalysts. The texture, physical/chemical properties, and reducibility of the flower-like Pt/CeO2 catalysts were characterized by X-Ray Diffraction （XRD）, Scanning Electron Microscope （SEM）, Transmission Electron Microscope （TEM）, N2 adsorption, and hydrogen temperature programmed reduction （HE-TPR） techniques. The catalytic performance of the catalysts for treating automobile emission was studied relative to samples prepared by the conventional wetness impregnation method. The Pt/CeO2 catalysts fabricated by this novel method showed high specific surface area and metal dispersion, excellent three-way catalytic activity, and good thermal stability. The strong interaction between the Pt nanoparticles and CeO2 improved the thermal stability. The Ce4＋ ions were incorporated into the surfactant chains and the Pt nanoparticles were stabilized through an exchange reaction of the surface hydroxyl groups. The SEM results demonstrated that the Pt/CeO2 catalysts had a typical three-dimensional （3D） hierarchical porous struc- ture, which was favorable for surface reaction and enhanced the exposure degree of the Pt nanoparticles. In brief, the flower-like Pt/CeO2 catalysts prepared by UAMR-hydrothermal method exhibited a higher Pt metal dispersion, smaller particle size, better three-way catalytic activity, and improved thermal stability versus conven- tional materials.
