Stability of Porous Platinum Nanoparticles: Combined In Situ TEM and Theoretical Study (original) (raw)
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Investigation into the Catalytic Activity of Porous Platinum Nanostructures
Langmuir, 2013
The catalytic activity of porous platinum nanostructures, viz platinum nanonets (PtNNs) and platinum nanoballs (PtNBs), synthesized by radiolysis were studied using two model reactions i) electron transfer reaction between hexacyanoferrate (III) and sodium thiosulfate and ii) the reduction of p-nitrophenol by sodium borohydride to p-aminophenol. The kinetic investigations were carried out for the platinum nanostructure catalyzed reactions at different temperatures. The pseudo-first order rate constant for the electron transfer reaction between hexacyanoferrate (III) and sodium thiosulfate catalyzed by PtNNs and PtNBs at 293 K are (9.1 ± 0.7) × 10 -3 min -1 and (16.9 ±0.6) × 10 -3 min -1 respectively. For the PtNNs and PtNBs catalyzed reduction of p-nitrophenol to p-aminophenol by sodium borohydride, the pseudo-first order rate constant was (8.4 ± 0.3) × 10 -2 min -1 and (12.6 ± 2.5) × 10 -2 min -1 respectively. The accessible surface area of the PtNNs and PtNBs determined before the reaction are 99 m 2 /g and 110 m 2 /g respectively. These nanostructures exhibit significantly higher catalytic activity, consistent with largest accessible surface area reported so far for the solid platinum nanoparticles. The equilibrium of the reactants on the surface of the platinum nanostructures played an important role in the induction time (t 0 ) observed in the reaction. A possible role of structural modifications of PtNBs catalyzed reaction leading to change in the accessible surface area of PtNBs is being explored to explain the non-linear behavior in the kinetic curve. The activation energy of the PtNNs and PtNBs catalyzed reduction of PNP are 26 kJ/mol and 6.4 kJ/mol respectively These observations open up new challenges in the field of material science to design and synthesize platinum nanostructures which could withstand such reaction conditions.
Surface properties of platinum catalysts based on various nanoporous matrices
Microporous and Mesoporous Materials, 2007
Platinum species was located via incipient wetness impregnation with chloroplatinic acid in the mesoporous silicate and niobiosilicate of MCM-41 type, microporous DHY zeolite containing $20% of mesopores, and in Y zeolite mixed with the mesoporous NbMCM-41 material. A choice of the supports was determined by their various chemical composition and structure/texture parameters leading to the different metal-support interactions and various location of platinum. N 2 adsorption/desorption measurements, XRD, 27 Al MAS NMR, and TOF-SIMS techniques were applied for the characterisation of the prepared materials. A special focus was on the latter method, which allows a complex characterisation of metal surroundings (oxygen, chloride ions) and its dispersion, as well as the components of the support. The most important finding from this work is the migration of oxygen located in Nb surrounding toward platinum species, which causes the higher content of Pt-oxygen species in NbMCM-41 than in SiMCM-41 matrix, migration of oxygen from Pt to Al species in Pt/DHY, and migration of Pt from Pt/Y to NbMCM-41. The other important conclusions are the presence of Pt-Cl species strongly held especially in the systems containing niobium and the protection against Pt agglomeration by the incorporation of Nb element into the catalytic systems. All these features influence the catalytic activity of Pt-containing materials.
Inorganica Chimica Acta, 2006
Well-defined Pt monodispersed nanoparticles within the catalytically relevant 1-10 nm size regime were synthesized in solution phase by several synthetic methods which differed in the choice of reducing agent, surface stabilizer, reaction temperature and solvent. Threedimensional model catalysts were fabricated by incorporating the metal nanoparticles into ordered channels of high surface area mesoporous oxides such as SiO 2 , Al 2 O 3 and Ta 2 O 5 through either sonication or direct synthesis of the oxide support around the particles. Deposition of the same nanocrystals onto silica supports by means of the Langmuir-Schaeffer technique produced two-dimensional model catalysts.
Applied Catalysis B: Environmental, 2019
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