TOF的计算方法_精品文档.pdf

1、 Supporting information for Synthesis of PtPd Bimetal Nanocrystals with Controllable Shape,Composition and Their Tunable Catalytic Properties Xiaoqing Huang,Yujing Li,Yongjia Li,Hailong Zhou,Xiangfeng Duan,and Yu Huang*Department of Materials Science and Engineering,Department of Chemistry and Bioch

2、emistry,and California NanoSystems Institute,Univer-sity of California,Los Angeles,California 90095,United States Email:yhuangseas.ucla.edu Experimental Details Chemicals:Sodium tetrachloropalladate(Na2PdCl4,99.9%),Potassium tetrachloroplatinate(K2PtCl4,99.9%),Sodium chloride(NaCl,ACS reagent,99.5%)

3、,Sodium bromide(NaBr,ACS reagent,99.5%),Sodium iodide(NaI,ACS reagent,99.5%),Poly(vinyl pyrrolidone)(PVP,MW55000)and N,N-dimethylformamide(DMF)were all purchased from Sigma-Aldrich.All the chemicals were used as received without further purification.The water(18 M/cm)used in all experiments was prep

4、ared by passing through an ultra pure purification system(Aqua Solutions).Synthesis of Cubic PtPd Nanocrystals:In a typical synthesis of cubic PtPd nanocrystals,sodium tetrachloropalladate(Na2PdCl4,20 mM,ie.0.67 mL,1.0 mL or 1.33 mL),potassium tetrachloroplatinate(K2PtCl4,20 mM,ie.1.33 mL,1.0 mL or

5、0.67 mL),sodium iodide(NaI,75.0 mg)and poly(vinylpyrrolidone)(PVP,160.0 mg)were mixed together with 10 mL N,N-dimethylformamide in a 22.0-mL vial.After the vial had been capped,the mixture was ultrasonicated for around 2 minutes.The resulting homogeneous mixture was transferred into a conventional o

6、ven and heated at 130 C for 5 hours before it was cooled to room temperature.The resulting colloidal products were collected by centrifugation and washed several times with an ethanol-acetone mixture.Synthesis of Octahedral PtPd Nanocrystals:In a typical synthesis of octahedral PtPd nanocrystals,sod

7、ium tetrachloropalladate(Na2PdCl4,20 mM,ie.0.67 mL,1.0 mL or 1.33 mL),potassium tetrachloroplatinate(K2PtCl4,20 mM,ie.1.33 mL,1.0 mL or 0.67 mL),sodium chloride(NaCl,29.3 mg)and poly(vinylpyrrolidone)(PVP,160.0 mg)were mixed together with 10 mL N,N-dimethylformamide in a 22.0-mL vial.After the vial

8、had been capped,the mixture was ultrasonicated for around 2 minutes.The resulting homogeneous mixture was transferred into a conventional oven and heated at 130 C for 5 hours before it was cooled to room temperature.The resulting colloidal products were collected by centrifugation and washed several

9、 times with an ethanol-acetone mixture.Characterization:TEM images were carried out on a FEI CM120 transmission electron microscope operated at 120 kV.High resolution TEM images and the high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM)-energy-dispersive X-ray spectr

10、oscopy(EDS)was were taken on a FEI TITAN transmission electron microscope operated at 300 kV.The samples were prepared by dropping ethanol dispersion of samples onto carbon-coated copper TEM grids(Ted Pella,Redding,CA)using pipettes and dried under ambient condition.X-ray powder diffraction patterns

11、 were collected on a Panalytical XPert Pro X-ray Powder Diffractometer with Cu-K radiation.The concentration of catalysts was determined by the inductively coupled plasma atomic emission spectroscopy(TJA RADIAL IRIS 1000 ICP-AES).General Procedure for Hydrogenation of Nitrobenzene:In a typical catal

12、ytic reaction,nitrobenzene(2.0 mmol),PtPd catalysts suspension in ethanol(0.1 mM,1.0 mL)and ethanol(9.0 mL)were mixed together and placed into a glass pressure vessel.In order to remove the air from the reaction system,the vessel was purged with H2 before the catalytic reaction.Then,the vessel was p

13、ressurized with 1 bar.During the catalytic experiment,the pressure of H2 was maintained constant.The intermediate catalytic products produced at different reaction time were analyzed by GC-MS.Turn-Over-Frequency(TOF)Calculations(a)General concept 1.TOF of the catalyst=(mole of nitrobenzene conversio

14、n)/(mole of surface atoms of catalyst reaction time)2.Since both Pd and Pt have a face-centered-cubic structure with a similar lattice constant(lattice constant of Pd is 0.389 nm,lattice constant of Pt is 0.392 nm),we collectively used a lattice constant of 0.39 nm in the alloyed PtPd nanocrystals f

15、or the simplicity of calculation.So,the volume of a unit cell in PtPd nanocrystals is(0.39 nm)3=0.059 nm3.Each unit cell contains 4 Pt&Pd atoms.3.An octahedron with an edge length of a has a surface area of 322a and a volume of 323a.An cube with an edge length of b has a surface area of 62band a vol

16、ume of 3b.4.PtPd octahedron is enclosed by 111 facet.Each two-dimensional unit cell on the 111 facets contains 0.5 Pt&Pd atoms.The area of this unit cell is 341268.2=0.031 nm2.PtPd nanocube is enclosed by 100 facet.Each two-dimensional unit cell on the 100 facets contains 2 Pt&Pd atoms.The area of this unit cell is(0.39 nm)2=0.15 nm2.(b)Number of Pt&Pd atoms in each PtPd nanocrystals Number of Pt&Pd atoms in each octahedral PtPd nanocrystals=(volume of each octahedron/volume of each unit cell)at