Controlled Synthesis Of Cu-Ni Bimetallic Nanocrystals And Their Catalytic Properties

Controlled synthesis of bimetallic nanomaterials which could be applied in many fields,such as heterogeneous catalysis,semiconductor industry and cryogenic fuel cell technology has become an important topic.Compared with single metal catalysts,bimetallic catalysts allow scientists to have more opportunities to change catalytic performance through modulating the electron transfer between different metals,local synergistic environments,lattice strain,and surface elemental distribution.In this paper,Cu-Ni bimetallic nanocrystals with different morphologies were prepared with a solvothermal method.The effect of coating agents,reaction time and temperature was discussed and the formation mechanism of nanocrystals was investigated.In addition,the nanocrystals with different morphologies were prepared as catalysts,and the catalytic activity was investigated by o-xylene catalytic oxidation experiments.For preparation of Cu-Ni bimetallic nanocrystals,aniline in benzyl alcohol solution was used as reducing agent,and then the Cu-Ni hexagonal nanoplates and nanowires with well-defined and uniform shape were controllably synthesized by altering the concentration of PVP.During this process,it was found that the final nanoparticles were inclined to be the hexagonal nanoplates at a relatively low concentration(0.2 mM)of PVP of the reaction.When the concentration of PVP was increased to 0.4 mM,the well-dispersed Cu-Ni nanowires dominated.Temperature was also plays an important role in influencing the growth of nanocrystals.It seems that temperature lower than 170 ? is nor in favor of nanoparticles growth,and the temperature higher than 220 ?would resulted in the ill-defined aggregates formation due to the rapidly raised nucleation rates and growth rates of nanoparticles.Cu-Ni bimetallic catalysts were prepared by different methods and applied in the catalytic oxidation experiment.The effect of different carriers,active phases and other factors was also investigated.Compared with the traditional incipient-wetness impregnation method,both Cu-Ni nanoplates and nanowires show better catalytic activities.Especially,the Cu-Ni nanowires supported mesoporous ZSM-5 zeolite(MZSM-5)catalyst with 11 wt%metal loading exhibited the most excellent catalytic performance.By comparing the values of T90(Temperature at which 90%conversion is attained),it can be found that the temperature of the nanowire catalyst is about 40? lower than that of the catalyst prepared by in-situ method,70 ? lower than that of the catalyst prepared incipient-wetness impregnation method.The main reason is that the catalyst could form a durian-like surface structure during the ultrasonic process,which leads to the better catalytic activity than other catalysts.