Studies On The Synthesis And Size Control Of Ruthenium And Cobalt Nanoparticles

The particle size of nano-materials ranges from 1 to 100 nm, which is in the boundary zone of atomic cluster and bulk substances with properties quite different from both the bulk material and individual atom or molecule. Nano-particles exhibit various specialities due to their small size including quantum size effect, surface effect, macroscopic quantum tunneling effect and dielectric confinement effect, which make nano-materials have many specific functions, and so they are applied in nano-mechanics, nano-electrics, magnetics, calorifics, nano-scale optics and catalysis. Their specific chemical and catalytic properties are different from those of the bulk materials. Thus, in recent years nano-materials and nano-technologies have been attached much importance in the scientific research and exploits, and have been regarded as the most prosperous technology field in the 21st century.Ruthenium and cobalt catalysts have been found to be the excellent catalysts for Fischer-Tropsch synthesis. The nano-technologies have been used to prepare catalysts of high efficiency and product selectivity. For Fischer-Tropsch synthesis catalysts, although active metal components in conventional catalysts are nanoparticles, the distribution of the particle size is wider. So it is not exact to investigate effect of the particle size and shape of nanoparticles on catalytic performance.In this work, the preparation methods were explored in controlling the particle size of ruthenium and cobalt nanoclusters and then the effect of preparation conditions on the particle size was investigated. The nanoparticles were characterized by means of TEM, XPS and FT-TR. The results are as follows:(1) Ru nanoparticles with narrow size distributions have been synthesized by chemical reduction of ruthenium nitrosyl nitrate in ethylene glycol using Poly (N-vinyl-2-pyrrolidone) as the stabilizer. In the one-step reaction, the average diameter of Ru nanoparticles was controlled in the range of 1.2-6.5 nm by changing the synthesis procedure and reaction conditions. In the seeding growth reaction, the Ru nanoparticle size was also successfully controlled, and ruthenium particles with different sizes (3.8-7.3 nm) were synthesized.(2) Co particles with different mean particle sizes in the range 3.2-171.4nm were synthesized by reduction of cobalt salt with sodium borohydride as the reducing reagent, using the organic solvent-stabilized method and / or in the presence of a triblock copolymer P123 (EO₂₀PO₇₀EO₂₀) as the surfactant. The particle size and its distribution were controlled by varying the synthesis parameters such as the viscosity of the medium, the amount of alcohols or P123 in the reaction system. FT-IR and XPS measurements confirmed the interaction between O atoms of P123 and Co²⁺ or Co⁰. Detailed surface analyses by XPS and HRTEM revealed that the synthesized particles consisted of Co⁰ metal surrounded by amorphous CoO, Co2B and chemisorbed P123.