Investigation into the Catalytic Activity of Porous Platinum Nanostructures

Abstract

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 pseudofirst-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 PtNN- and PtNB-catalyzed reduction of p-nitrophenol to p-aminophenol by sodium borohydride, the pseudofirst-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 and 110 m(2)/g, respectively. These nanostructures exhibit significantly higher catalytic activity, consistent with the 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 (t0) observed in the reaction. A possible role of structural modifications of PtNBs catalyzed the reaction leading to change in the accessible surface area of PtNBs is being explored to explain the nonlinear behavior in the kinetic curve. The activation energy of the PtNN- and PtNB-catalyzed reduction of p-nitrophenol are 26 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.

Mesoporous Colloidal Superparticles of Platinum‐Group Nanocrystals with Surfactant‐Free Surfaces and Enhanced Heterogeneous Catalysis

“…For example, the assembly of chemically synthesized nanoparticles into network architectures has been proven to exhibit enhanced catalytic activity in comparison with the original mono dispersed Pt nanoparticles. [ 37,38 ] Despite of this enhancement, there is still a room to further improve the catalytic performance if the capping species can be removed from the Pt nanostructures. Although conventional thermal annealing can burn away the capping species from the assembled porous architectures, it can sinter the Pt nanoparticles and greatly decrease the porosity in the architectures.…”

Pt-content-controlled synthesis of Pd nanohollows/Pt nanorods core/shell composites with enhanced electrocatalytic activities for the methanol oxidation reaction

“…It is easy to understand that hollow or porous Pd/Pt nanostructures are favorable to improve Pt utilization efficiency and enhance their catalytic activity due to their high surface-to-volume and surface permeability [25,26]. For example, Xia's group has demonstrated that the PdePt nanocages exhibit stronger catalytic activity and selectivity for the preferential oxidation of CO in excess hydrogen than Pd nanocubes and commercial Pt/C because of its alloy composition and hollow structure [27].…”

Synthesis of spherical copper-platinum nanoparticles by sonoelectrochemistry followed by conversion reaction

“…However, as conversion is made under stirring, O 2 dissolution inside solution appears gradually and leads to a weak oxidation of Cu according Eq. (7). This phenomenon explains why the platinum atomic percentage value is slightly superior to the maximal one.…”

“…(3)) becomes negligeable but oxygen continues to react with accessible copper according to Eq. (7). It results in a break on the curve.…”

“…This interest for nanoparticles can be explained by their various fields of application. Among them, medicine (cancer therapy [1,2], IRM contrasting agent [3] or drug delivering [4]), sensors [5], energy storage [6] and catalysis [7,8] can be cited. Nanoparticles are characterized by a high surfaceto-volume ratio.…”