Preparation of Pt Nanoparticles Dispersed in Mesoporous Silica
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1217-Y08-24
Preparation of Pt nanoparticles dispersed in mesoporous silica Yukitoshi Chiba1, Hirobumi Shibata1, Daichi Nagata1, Takahiro Gunji2, Ryuji Tamura1, Tohru Kineri3 and Keishi Nishio1 1
Department of Materials Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda-shi, Chiba 278-8510, Japan 2 Department of Pure and Applied Chemistry, Tokyo University of Science, 2641 Yamazaki, Noda-shi, Chiba 278-8510, Japan 3 Department of Applied Chemistry, Tokyo University of Science, Yamaguchi, 1-1-1 DaigakuDori, Sanyoonoda-shi, Yamaguchi 756-0884, Japan ABSTRACT Platinum nanoparticles were dispersed in mesopores of mesoporous silica using a sol-gel process with a composite template consisting of an amphiphilic triblock copolymer (Pluronic P123 or F127) and a Pt-organic complex, which was prepared with K2Pt(II)Cl4 as a Pt source and 1,10-phenanthroline as a chelating agent. The obtained Pt-1,10-phenanthroline complex did not dissolve in any of several solvents, e.g., hexane, benzene, toluene, THF, H2O, CH3OH, and C2H5OH. However, when the Pt-1,10-phenanthroline complex was reacted with ethylenediamine it dissolved in many solvents. Platinum nanoparticles dispersed in mesoporous silica were obtained using a sol-gel process with a complex template consisting of Pt-1,10-phenanthrolineethylenediamine, and an amphiphilic triblock copolymer (Pluronic P123 or F127). A sample dried at 353 K was bright yellow. When it was subsequently heat-treated at 823 K, it turned light gray. This change indicates that Pt nanoparticles can be obtained by heat-treatment at high temperature, because, to generate Pt nanoparticles, the organics chelated to Pt ions must be removed. Measurements from small-angle x-ray scattering show that mesoporous silica obtained using a complex template has a much more highly ordered pore structure than that obtained using only an amphiphilic triblock copolymer. It has both large pores (above 8 nm) and a large surface area (about 290 m2/g). Furthermore, results of a TEM investigation showed that Pt nanoparticles were generated only in mesopores of mesoporous silica. INTRODUCTION Pt is used as a catalyst for fuel cell electrodes and exhaust gas [1]. Pt is a heterogeneous catalyst, and catalyst activity increases with surface area. However, microparticulation, in which fine particles easily agglutinate and fly apart, is a problem. One solution is supporting catalyst particles in chemical and thermal stable inorganic solid materials with large specific surface area and appropriate pore size for the catalyst nanoparticle. We focused on mesoporous silica, one such material. Mesoporous silica has a highly ordered pore structure (about 2-20 nm) and high specific surface area. Mesoporous silica is being widely studied due to its potential applications in catalysts, medical devices, absorbents, and separating materials [2–7]. Dispersing and supporting the catalytic particles in mesopores of mesoporous silica prevents them from aggregating and increases the amount of gaseous surface adsorption. Therefo
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