Studies of the factors effecting the preparation of heterogeneous platinum-based catalyst on silica supports

Pt nanoparticles with an average size of ∼3 nm were successfully immobilized on the surface of SiO2 functionalized with -NH2 and -SH groups through chemical reduction process using polyvinylpyrrolidone as a stabilizer and different reducing agents. The effects of molecular weight of polyvinylpyrrolidone, molar ratio of reducing agent to Pt salt, type of reducing agent on the size and degree of agglomeration of Pt nanoparticles on the SiO2 surface were investigated. The X-ray diffraction and transmission electron micrograph analyses were performed to identify the product phase, size and morphology of immobilized Pt onto SiO2. UV-vis analysis was also conducted to identify the degree of reduction of Pt ions. The Pt-SiO2 nanocomposite prepared from both NH2- and SH-functionalized SiO2 exhibited similar behavior. The number of immobilized Pt nanoparticles and their average size was increased with polyvinylpyrrolidone concentration while the number of immobilized Pt was decreased with its molecular weight.