Silica Coated Co,Ni,Cu,Pt Based Multi-metallic Nanoparticles (or Clusters) Synthesized From Reverse Microemulsion And Their Properties

Multimetallic nanoparticles or clusters,consisting of two or more distinct elements and limited number of atoms,have received considerable interest due to their unique optical,electronic and magnetic properties.Meanwhile,reverse microemusion has been proved to be an efficient method for the preparation of composite nanomaterials.However,the synthesis of multimetallic nanoparticles or clusters from reverse microemusion with controllable structures,sizes and compositions still remain challenges.In this thesis,a new method based on reverse microemusion was proposed for the preparation of multimetallic nanoparticles or clusters.Firstly,silica coated copper oxide clusters with controllable sizes were synthesized(CuO@SiO2).The reversible thermochromism property of CuO@SiO2 based on the enhanced thermosensitive band gap of CuO clusters was obseverd and studied.The colour of CuO@SiO2 can change from light blue at 20 ? to green at 500 ?.Due to the confinement of CuO clusters by the microporous silica,CuO@SiO2 maintained the original structure and porperties after 10 times of thermochromism cycling.Silica coated zinc oxide clusters(ZnO@SiO2)and mixed metal oxide clusters were prepared by the same method.Silica coated CuNi bimetallic nanoparticles(CuNi@SiO2)were prepared by co-reduction of silica coated CuO/NiO clusters under H2 at high temperature.CuNi bimetallic nanoparticles with the average sizes of 2.7 ± 0.5 nm,4.6 ± 0.4 nm,5.7 ± 0.4 nm and 7.8 ± 0.5 nm,also composition of Cu86Ni14,CU54Ni46 and Cu29Ni71 were prepared by simply varying the volume and concentration of precursor solutions.The reduction of p-nitrophenol by NaBH4 was chosen as model reaction to evaluate the catalytic activity of CuNi@SiO2.The as-prepared CuNi@SiO2 displayed higher activity and lower activation energy compared with Cu@SiO2 and Ni@SiO2.Silica coated CoCu bimetallic nanoparticles(CoCu@SiO2)were prepared by the same method.Platinum decorated CoCu bimetallic nanoparticles coated by silica(Pt-CoCu@SiO2)were synthesized by a facile spontaneous displacement reaction by using CoCu@SiO2 and H2PtCl6 as the starting materials.Pt-COCu@SiO2 with 0.43 wt%,0.75 wt%and 1.38 wt%loading amount of Pt were prepared with different concentration of H2PtCl6 aqueous solution.The catalytic activity of Pt-CoCu@SiO2 for hydrogen production from hydrolysis of ammonia-borane(NH3·BH3;AB)was tested.An impressive turnover frequency(TOF)value of 272.8 molH2 · molpt-1·min-1 was achieved at the hydrolysis temperature of 30 ?.In addition,Pt-CoCu@SiO2 showed high stability for the hydrogen production from AB in six runs.Further,silica coated nickel/nickel oxide clusters(Ni/NiO@SiO2)were synthesized from reverse microemusion.PtNi/NiO@SiO2 were prepared by the same spontaneous displacement reaction,by converting the extra Pt4+ to Pt0 under H2,R-PtNi/NiO@SiO2 were generated.R-PtNi/NiO@SiO2 with 0.095 wt%,0.18 wt%,0.34 wt%,0.48 wt%and 0.71 wt%loading amount of Pt were synthesized by only changing the concentration of H2PtCl6.The TOF value for catalytic hydrogen production from hydrolysis of AB reached 1240.3 molH2 · molPt-1 · min-1,which is one of the most active Pt based catalysts ever reported for this reaction.