Surface Of Platinum Nanoparticles Research Articles

A voltammetric method of measuring the specific surface area and amount of platinum in microsamples of electrode material and membrane-electrode assembly of hydrogen fuel cells

A method based on cyclic voltammetry is proposed for determining platinum content, measuring the specific area of the active surface of platinum nanoparticles, and studying the dynamics of these values in a small amount (micrograms) of sample material.

Probing the surface of platinum nanoparticles with13CO by solid-state NMR and IR spectroscopies

The synthesis and full characterization of platinum nanoparticles (Pt NPs) prepared by decomposition of the Pt(dba)2 complex in the presence of CO and H2 and stabilized either sterically by a polymer, polyvinylpyrrolidone or chemically by a ligand, diphenylphosphinobutane, are reported. In these studies, (13)CO was used as a probe molecule to investigate the surface of the particles, using IR and solid-state NMR spectroscopies with magic angle spinning (MAS-NMR). Three nanosystems with different sizes are described: Pt/PVP/(13)CO (monomodal: 1.2 nm), Pt/dppb/(13)CO (bimodal: 1.2 nm and 2.0 nm) and Pt/dppb/H2 (monomodal: 2.0 nm) NPs. Spectroscopic data suggest a modification of the electronic state of the nanoparticles between 1.2 nm and 2.0 nm which can be related to the presence of Knight shift.

An easy one-step photocatalytic synthesis of 1-aryl-2-alkylbenzimidazoles by platinum loaded TiO2 nanoparticles under UV and solar light

One-pot synthesis of disubstituted benzimidazoles from N-substituted 2-nitroanilines or 1,2-diamines with 3–12nm-sized platinum particles loaded on the TiO2 using solar and UV-A light is described. 1-Aryl-2-alkylbenzimidazoles from 2-nitrodiphenylamines are formed by combined redox photocatalytic reaction, condensation and catalytic dehydrogenation on Pt-TiO2. In case of diamines, this reaction is proceeded by Pt-TiO2 assisted photocatalytic oxidation of an alcohol and a catalytic dehydrogenation of the intermediate on the surface of platinum nanoparticles. In both cases product formation was achieved by tandem photocatalytic and catalytic reactions on Pt-TiO2.

Preparation of PtcoreAgshell nanoparticles: Catalytic reduction of Ag+ ions by hydrogen

It is shown that the saturation of an aqueous solution containing silver ions with hydrogen in the presence of 9.5-nm platinum nanoparticles leads to the reduction of silver and the formation of PtcoreAgshell bimetal nanoparticles. An increase in the concentration of silver ions gives rise to a number of elementary silver layers that cover the platinum core. It is established that the concentration of silver ions does not substantially affect the rate of the formation of a silver shell on the surface of platinum nanoparticles.

One‐Pot Synthesis of Benzimidazoles by Simultaneous Photocatalytic and Catalytic Reactions on Pt@TiO2 Nanoparticles

Dual platinum action: A one-pot catalytic synthesis of benzimidazoles from the photoirradiation of an alcohol solution containing an ortho-arylenediamine and Pt@TiO2 nanoparticles is described. This reaction proceeded by the platinum-assisted photocatalytic oxidation of an alcohol and a catalytic dehydrogenation of the intermediates on the surface of platinum nanoparticles.

In Situ and Real-Time Monitoring of Oxide Growth in a Few Monolayers at Surfaces of Platinum Nanoparticles in Aqueous Media

The electrochemical oxidation behaviors of the surfaces of platinum nanoparticles, one of the key phenomena in fuel cell developments, were investigated in situ and in real time, via time-resolved hard X-ray diffraction and energy dispersive X-ray absorption spectroscopy. Combining two complementary structural analyses, dynamical and inhomogenous structural changes occurring at the surfaces of nanoparticles were monitored on an atomic level with a time resolution of less than 1 s. After oxidation at 1.4 V vs RHE (reversible hydrogen electrode) in a 0.5 M H(2)SO(4) solution, longer Pt-O bonds (2.2-2.3 A that can be assigned to OHH and/or OH species) were first formed on the surface through the partial oxidation of water molecules. Next, these species turned to shorter Pt-O bonds (2.0 A, adsorbed atomic oxygen), and atomic oxygen was incorporated into the inner part of the nanoparticles, forming an initial monolayer oxide that had alpha-PtO(2)-like local structures with expanded Pt-Pt bonds (3.1 A). Finally, quasi-three-dimensional oxides with longer Pt-(O)-Pt bonds (3.5 A, precursor for beta-PtO(2)) grew on the surface, at almost 100 s after oxidation. Despite the very complex oxidation mechanism on the atomic level, XANES analysis indicated that the charge transfer from platinum to the adsorbed oxygen species was almost constant and rather small, that is, about 0.5 electrons per oxygen, up to two monolayers of oxygen. This means that ionic polarization hardly develops at this stage of the surface platinum's "oxide" growth.

Nanocomposite Langmuir–Blodgett films based on crown derivatized platinum nanoparticles: Synthesis, characterization, and electrical properties

This paper deals with the crown derivatization of 4-mercaptoaniline functionalized platinum formation and the use of the resulting nanoparticles to build up controlled Langmuir and Langmuir–Blodgett films. It is shown that the high density of amine functions at the surface of platinum nanoparticles functionalized by 4-mercaptoaniline offers the possibility of over grafting with various molecules giving rise to different rate of crown derivatization ranging from 19% to 45%. The derivatizations process of the organic coating has been characterized by infrared spectroscopy and thermo gravimetric analysis. The elaboration of Langmuir and Langmuir–Blodgett films containing different ratio of derivatized nanoparticles and fatty acid is reported and the thin films are characterized using X-ray photoelectron spectroscopy and small-angle X-ray scattering. A marked structural anisotropy due to the deposition process is revealed, that corresponds in some cases to a well-defined layered organisation. Modifications in electrical conductivity induced by crown derivatization are reported. These crown derivatized particles are currently studied towards the oxygen reduction reaction.

Microwave-Assisted Synthesis of Platinum Nanoparticles

The rapid synthesis of platinum nanoparticles using ethylene glycol and microwave dielectric heating is reported here. The Pt nanoparticles after synthesis were transferred to a toluene solution of dodecanethiol (DDT) to form DDT-encapsulated Pt nanoparticles. The TEM examinations showed nearly spherical platinum nanoparticles. The particles were in the size range of 2~8 nm and exhibited narrow size distribution. They were stable in the toluene solution for at least 10 months. Larger particles were formed with longer microwave heating time, higher metal precursor salt concentrations, and lower pH values. XPS measurements revealed >80% of Pt was in the zero valent state and the S 2p signal showed strong adsorption of sulfur species on the surface of platinum nanoparticles. FTIR spectroscopy also confirmed the interactions of thiol groups and the platinum surface.

Phase transfer of platinum nanoparticles from aqueous to organic solutions using fatty amine molecules

In this report we demonstrate a simple process based on amine chemistry for the phase transfer of platinum nanoparticles from an aqueous to an organic solution. The phase transfer was accomplished by vigorous shaking of a biphasic mixture of platinum nanoparticles synthesised in an aqueous medium and octadecylamine (ODA) in hexane. During shaking of the biphasic mixture, the aqueous platinum nanoparticles complex via either coordination bond formation or weak covalent interaction with the ODA molecules present in the organic phase. This process renders the nanoparticles sufficiently hydrophobic and dispersible in the organic phase. The ODA-stabilised platinum nanoparticles could be separated out from hexane in the form of a powder that is readily redispersible in weakly polar and non-polar organic solvents. The ODA-capped platinum nanoparticles show high catalytic activity in hydrogenation reactions and this is demonstrated in the efficient conversion of styrene to ethyl benzene. The nature of binding of the ODA molecules to the platinum nanoparticles surface was characterised by thermogravimetry, transmission electron microscopy (TEM), X-ray photoemission spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR)

Steps, ledges and kinks on the surfaces of platinum nanoparticles of different shapes

Platinum nanoparticles with a high percentage of cubic-, tetrahedral- and octahedral-like shapes, respectively, have been synthesized by a shape-controlling technique that we developed recently [Ahmadi et al., Science 272 (June 1996) 1924]. High resolution transmission electron microscopy (HRTEM) is used here to directly image the atomic scale structures of the surfaces of these particles with different shapes. The truncated shapes of these particles are mainly defined by the {100}, {111}, and {110} facets, on which numerous atom-high surface steps, ledges and kinds have been observed. This atomic-scale fine structure of the surfaces of these particles is expected to play a critical role in their catalytic activity and selectivity.