Study On The Preparation And Catalytic Properties Of The Bimetallic Nano-materials

Nano-materials lie in the region between the macroscopic materials and microscopic atoms or molecules on the scale. Their specific physicochemical properties differ from the macroscopic materials and microscopic atoms/molecules and they are widely applied in the fields of catalysis, environmental science, biological medicine, energy, information technology, military equipment and aerospace, etc.As a branch of nano-materials, metallic nano-materials have been applied in many fields because of their excellent optical, electrical, thermal and magnetic properties. Although the monometallic nano-catalysts show good performance in varied reactions, there are still problems such as limited activity, low selectivity, unsatisfactory poison resistance and poor stability. It is found that introducing another metallic element to form alloy or nano-composite is an effective way to solve the above problems. Regulating the composition and structure of bimetallic catalysts can enhance the catalytic performance significantly. Nowadays, the research on how to prepare the bimetallic nano-material with specific composition and structure and exploring the interaction between the two metals is still not deep enough. Therefore, we aim to intensively study these issues and the main contents are as followed:Ⅰ. The Cu-Ag bimetallic nano-composite:(1) We prepared the Ag nanoparticles, Cu nanoparticles and Cu-Ag bimetallic nano-materials with different compositions by using chemical reduction method and further confirmed that the Cu and Ag existed in the form of phase separation state for the Cu-Ag bimetallic nano-materials by means of various physical and chemical characterizations.(2) The reduction of 4-nitrophenol was used as a probe reaction to explore the interactions between Cu and Ag in the nano-composites. The catalytic activities of the above nano-composites were composition dependent and the Ag75Cu25 nano-composite possessed the best catalytic activity among our synthesized catalysts. By comparing the catalytic properties of mechanical mixed Ag and Cu nanoparticles with that of Ag75Cu25 nano-composite, we further confirmed the electronic regulation and electron transference between Ag and Cu in the Cu-Ag composites and the direction of the electron transference was from Ag to Cu.Ⅱ. The Ag-Pd bimetallic alloy:(1) We prepared the Ag nanoparticles, Pd nanoparticles and Ag-Pd bimetallic alloy with different compositions by using the chemical reduction method and further confirmed the alloy structure.(2) The catalytic activity on the reduction of the 4-nitrophenol was composition dependent and the Ag90Cu10 alloy possessed the best catalytic activity among our synthesized catalysts. Comparing the catalytic properties of mechanical mixed Ag and Pd nanoparticles with the Ag90Cu10 alloy, we confirmed the electronic regulation between Ag and Pd. We further applied the catalysts to the electro-oxidation of methanol, the results showed that the Ag nanoparticles had little catalytic activity on the electro-oxidation of methanol and Ag-Pd alloys with different compositions were superior to Pd nanoparticles in the aspects of activity, stability and toxicity resistance.The above results provided more experimental proofs for understanding the structure of bimetal alloys/nano-composites and the interactions between the components. The results also helped to design other bimetallic catalysts with superior performance.