Synthesis of Nearly Uniform Pt Clusters in Aqueous Solutions and on a G-Al2O3 Surface

Conventional techniques widely used for the preparation of supported metal catalysts usually offer limited control over the size of the metal particles. Alternative synthetic routes based on the deposition of metal colloids have been suggested for better control of metal particles size. However, the use of metal colloids typically requires the chemical reduction of transition metal salts in aqueous media in the presence of templating agents and surfactants in order to stabilize the metal nanoparticles formed. A novel approach to the synthesis of stable Pt clusters in aqueous solutions, which is based on the chemical reduction of H₂PtCl₆ with NaBH₄ without the use of any surfactants or templating agents, was suggested in this work. This technique leads to the formation of nearly uniform Pt clusters that remain intact upon deposition onto a g-Al2O3 support. UV-Vis spectroscopy, Extended X-ray Adsorption Fine Structure spectroscopy (EXAFS), and FT-IR spectroscopy were used to characterize the morphology of the Pt clusters in the solution, on the g-Al₂O₃ surface, and during the catalytic conversion of isopropyl alcohol to acetone. In addition, the activity of the Pt/g-Al₂O₃ catalyst was evaluated in the gas phase CO oxidation.