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, Pt(3)Ti, has been synthesized in the form of nanoparticles (NPs) dispersed on silica (SiO(2)) supports. The organometallic Pt and Ti precursors, Pt(1,5-cyclooctadiene)Cl(2) and TiCl(4)(tetrahydrofuran)(2), were mixed with SiO(2) and reduced by sodium naphthalide in tetrahydrofuran. Stoichiometric Pt(3)Ti NPs with an average particle size of 2.5 nm were formed on SiO(2) (particle size: 20-200 nm) with an atomically disordered FCC-type structure (Fm3m; a = 0.39 nm). A high dispersivity of Pt(3)Ti NPs was achieved by adding excessive amounts of SiO(2) relative to the Pt precursor. A 50-fold excess of SiO(2) resulted in finely dispersed, SiO(2)-supported Pt(3)Ti NPs that contained 0.5 wt % Pt. The SiO(2)-supported Pt(3)Ti NPs showed a lower onset temperature of catalysis by 75 degrees C toward the oxidation reaction of CO than did SiO(2)-supported pure Pt NPs with the same particle size and Pt fraction, 0.5 wt %. The SiO(2)-supported Pt(3)Ti NPs also showed higher CO conversion than SiO(2)-supported pure Pt NPs even containing a 2-fold higher weight fraction of Pt. The SiO(2)-supported Pt(3)Ti NPs retained their stoichiometric composition after catalytic oxidation of CO at elevated temperatures, 325 degrees C. Pt(3)Ti 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.

Enhanced Activity for Oxygen Reduction Reactions by Carbon-supported High-index-facet Pt-Ti Nanoparticles

“…The precursor for Ti, Ti(tetrahydrofuran) 2 Cl 4 , was synthesized from TiCl 4 and distilled THF according to literature procedures. [9][10][11] Precursor solutions were prepared by dissolving 0.04 mmol (14.89 mg) of Pt(1,5-cyclooctadiene)Cl 2 , 0.16 mmol of Ti(tetrahydrofuran) 2 Cl 4 (53.42 mg) and 250 mg of CB (Vulcan XC-72R (E-TEK)) in 20 mL of distilled THF under a dry Ar atmosphere. The precursor solutions were then transferred into a syringe.…”

“…The products were air-stable, black powders. [9][10][11] The Pt-Ti NPs/ CB were annealed in vacuum at different temperatures for 1 hour. Pt NPs/CB was also prepared by a wet-chemical approach using lithium triethylborohydride as a reducing agent.…”

Ordered intermetallic Pt–Cu nanoparticles for the catalytic CO oxidation reaction

“…It has been proved that the intermetallic phase of Pt-Ti has approximately 20% less adsorption energy than that of pure Pt due to the changes in the electronic structure of Pt. [23][24][25] In addition, the component metals of the intermetallic phase, however, in some cases, provide adsorption sites for O 2 , whereas Pt provides adsorption sites for CO (dual site mechanism) in the intermetallic alloys. 26,27 Intermetallic alloys possess both unique surface structures and bulk properties compared to that of usual alloys or component metals that are used extensively for superconductivity, hydrogen storage, and shape-memory related applications.…”

Carbon-Supported Ordered Pt-Ti Alloy Nanoparticles as Durable Oxygen Reduction Reaction Electrocatalyst for Polymer Electrolyte Membrane Fuel Cells

“…As the intermetallic ordered structure of Pt alloy nanoparticles has been reported to enhance their durability, mainly because of diminished transition metal dissolution [6][7][8][9][10][11], ordered Pt-Ti alloy nanoparticles have been expected to show higher durability than disordered Pt-Ti alloy nanoparticles. A few groups have reported that carbon-supported ordered Pt-Ti alloy nanoparticles could be prepared via wet chemical approaches, unlike Pt alloys with Y, Sc, or Zr [12,13]. Ti 3+ can be reduced by strong reducing agents such as sodium naphthalenide [14] and potassium triethylborohydride [15].…”