Pt3Ti Nanoparticles: Fine Dispersion on SiO2Supports, Enhanced Catalytic CO Oxidation, and Chemical Stability at Elevated Temperatures

Abstract

A platinum-based intermetallic phase with an early d-metal, Pt₃Ti, has been synthesized in the form of nanoparticles (NPs) dispersed on silica (SiO₂) supports. The organometallic Pt and Ti precursors, Pt(1,5-cyclooctadiene)Cl₂ and TiCl₄(tetrahydrofuran)₂, were mixed with SiO₂ and reduced by sodium naphthalide in tetrahydrofuran. Stoichiometric Pt₃Ti NPs with an average particle size of 2.5 nm were formed on SiO₂ (particle size: 20−200 nm) with an atomically disordered FCC-type structure (Fm3̅m; a = 0.39 nm). A high dispersivity of Pt₃Ti NPs was achieved by adding excessive amounts of SiO₂ relative to the Pt precursor. A 50-fold excess of SiO₂ resulted in finely dispersed, SiO₂-supported Pt₃Ti NPs that contained 0.5 wt % Pt. The SiO₂-supported Pt₃Ti NPs showed a lower onset temperature of catalysis by 75 °C toward the oxidation reaction of CO than did SiO₂-supported pure Pt NPs with the same particle size and Pt fraction, 0.5 wt %. The SiO₂-supported Pt₃Ti NPs also showed higher CO conversion than SiO₂-supported pure Pt NPs even containing a 2-fold higher weight fraction of Pt. The SiO₂-supported Pt₃Ti NPs retained their stoichiometric composition after catalytic oxidation of CO at elevated temperatures, 325 °C. Pt₃Ti NPs show promise as a catalytic center of purification catalysts for automobile exhaust due to their high catalytic activity toward CO oxidation with a low content of precious metals.