Preparation Of Ag/SiO₂ Catalysts In Microemulsion And Its Activity In Hydrogen Peroxide Decomposition

The preparation of highly active catalysts for the decomposition of hydrogenperoxide is of significance for aerospace. Nano Ag/SiO2 supported catalysts weresuccessfully prepared with microemulsion method in this paper. TEM, XRD andUV-Vis spectra were examined to get insight into the depositing process, and thecatalytic activities for the decomposition of hydrogen peroxide were evaluatedwith an exhaust equipment. The main results could be summarized as follows:Making use of the commercial colloidal silica for the first time, whichpossesses huge specific surface area, and can easily absorb silver nanoparticles toform supported Ag/SiO2 catalysts, a novel deposition method was development inmicroemulsion. This method had the merits of readily operate and depositcompletely. The dosage of organic solvent is small, and silver nanoparticles arelocated on the surface of the support and not easy to be embedded in. The averagesize of the silver nanoparticles is 10 nm with a narrow size distribution. UV-Visspectra results showed that an interaction between silver particle and colloidalsilica is formed, which is assumed to facilitate the adhesion and dispersion ofsilver nanoparticles on silica surfaces. Unique particle size and shape controlfunction of microemulsion has been testified by changing the constitutes ofmicroemulsion and preparing conditions such as reaction time, dropping rate ofdestabilization agent and temperature of the microemulsion in some extent.Unexpectedly, chain-like silver nanoparticles were obtained. Ag/SiO₂ catalysts prepared with the above colloidal deposition methodexhibit an extremely high catalytic activities for the decomposition of hydrogenperoxide, and the rate constant values are two or three magnitudes of that obtainedby traditional impregnation method. This improvement could be ascribed to thedecrease of silver particle size and its highly dispersion on silica surface. Thecomposition of microemulsion along with the sorts of reduction and some otherpreparing conditions are tested to affect the catalytic activities of hydrogenperoxide decomposition heavily, which is closely correlated with the surfaceproperties of catalyst. The gives further evidence that preparing conditions has thefunction of control the silver particle size and its morphology.