Colloidal techniques were used to synthesize monodisperse Pt nanoparticles of four distinct sizes between 2 and 7 nm before immobilization onto silica. Ethylene hydrogenation demonstrated structure-insensitive behavior with TOFs of ∼12 s–1 before poisoning. With thiophene being a strong binding adsorbate, TOFs decreased by orders of magnitude, and the poisoning-induced antipathetic structure sensitivity because thiophene adsorbed more strongly to the coordinatively unsaturated, as compared with coordinatively saturated, surfaces, and the degree of saturation increased with decreasing Pt size. This effort is part of a broader study in which structure sensitivity is analyzed for adsorbates in complex reaction networks.

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The stability of precious metals under acidic conditions is a potential challenge for several applications, including proton exchange membrane fuel cells (PEMFCs). Strategies addressing this problem have been tested, including the addition of organic stabilizing agents such as polypyrrole. Organic stabilizing agents also have been used to synthesize precious metal nanoparticles by assisting in the regulation of the nucleation and growth rates. In this study, the stability of 3 nm Pt nanoparticles, synthesized using polyvinylpyrrolidone (PVP) as a capping agent, under acidic conditions was assessed. Well-defined 3 nm Pt nanoparticles were synthesized using a combination of metal precursor, Hexachloroplatinic acid (H2PtCl6), surfactant (PVP), alcohol (methanol), and water. The metal ion reduction rate was controlled by choosing an appropriate alcohol concentration and surfactant amount. Electrocatalytic properties of the nanoparticles were investigated using cyclic voltammetry electrochemistry experiments, to determine the corresponding electrochemical stability. Batches of washed (in cycles of hexane and ethanol) and unwashed nanoparticles were cycled between the hydrogen and oxygen reduction potentials. Results from the electrochemistry experiment were further correlated with temperature-programmed oxidation experiments after supporting the nanoparticles on silica. Detailed results of this work are presented in this paper, and potential implications for the oxygen reduction reaction and PEMFCs are discussed.