Synthesis And Catalytic Activity Of Au And Au-Pd Doublemetal Nanoparticles

In 1980s Haruta found that 2-5 nm Au particles supported on basic metal oxides were highly active in CO oxidation at low temperature.Since then,Au catalysts gained much attentions and widely used to catalyze a variety of reactions such as selective oxidation,selective hydrogenation,water-gas shift reaction and coupling reaction.This dissertation focuses on the controllable synthesis of Au and Au-Pd nanoparticles and their catalytic applications,and includes the following three parts:Gold colloids with a mean diameter of 1.9 nm were synthesized with PVA as the protecting reagent,and then deposited on MgO,?-Al2o3,TiO2,Fe2O3,Co3O4,ZnO and In2O3.After calcinations at 300 ? in air to remove PVA,Au NPs with the comparable mean diameter in the narrow range of 2.5-3.1 nm were obtained.These Au/oxides catalysts were further used to catalyze selective hydrogenation of cinnamaldehyde(CAL)to cinnamyl alcohol(COL).It was found that the selectivity of COL was tightly related to the acidity/basicity of the Au/oxides catalysts.Based on NH3-TPD and CO2-TPD measurements,the synergistic cooperation of acidic sites and basic sites on the Au/In2O3 and Au/ZnO catalyts should be responsible for the preferential adsorption and activation of the C=O group than C=C group.Au-Pd doublemetal nanoparticles with a mean diameter of 1.8 nm were first prepared and then deposited on CeO2.The resulting Au-Pd/CeO2 catalysts were well-characterized by FT-IR,TEM and XPS and then used to catalyze the selective hydrogenation of unsaturated aldehydes and ketones.It was found that Au-Pd/CeO2 could efficiently catalyze the preferential hydrogenation of C=C gourps compared with C=O groups,and the selectivity to saturated aldehydes was very high,even higher than 99%.The activity was strongly dependent on the electronic and steric features of the substrates caused by the substitution of functional groups.2-(diphenylphosphino)pyride protected Au nanoclusters were used as the precursors for etching by 2-naphthalenethiol(2-Nap)at different temperatures.At the etching temperature of 80?,atomically precise Au25(2-Nap)18 nanoclusters were prepared.If the etching temperature was lowered to 50 ?,atomically precise Au36(2-Nap)24 nanoclusters were obtained.In addition,the extension of reaction time was beneficial to the synthesis of both Au25(2-Nap)18 and Au36(2-Nap)24.