Electrochemical Behavior and Shape Evolution of Structured Pd Nanoparticles in Alkaline Media─Influence of Electrochemically Absorbed Hydrogen.

We report on the electrochemical behavior and shape evolution of Pd nanocubes (Pd NCs) and Pd nanooctahedrons (Pd NOs) with an average size of 9.8 and 6.9 nm, respectively, in aqueous alkaline medium in the potential range of the underpotential deposition of H (UPD H) and H absorption.

Characterization of platinum nanoparticles for fuel cell applications by single particle inductively coupled plasma mass spectrometry.

The most effective utilization of platinum (Pt) in fuel cells is achieved through the use of nanoparticles (NPs) that offer a large electrochemically active surface area. Because the stability of NPs decreases as they become smaller, their size and size distribution must be known in order to optimize the catalysts' durability, while offering high catalytic activity. Single particle inductively coupled plasma mass spectrometry (spICPMS) can quantify the mass of metallic NPs suspended in aqueous medium, which can then be converted into a size if the NPs' shape, density and composition are known.

Pd-Shaped Nanoparticles Modified by Gold ad-Atoms: Effects on Surface Structure and Activity Toward Glucose Electrooxidation.

Palladium nanoparticles (Pd-NPs) with controlled distributions of sizes and shapes (nanospheres-Pd-NS-, nanocubes -Pd-NC-, and nanooctahedrons -Pd-NO-) are synthesized by wet chemistry methods and characterized by TEM/HRTEM. The surfaces of Pd-NPs are modified by spontaneous adsorption of gold and characterized by cyclic voltammetry in acidic medium. It is shown that the modification of Pd-NPs by dipping in HAuCl solutions of different concentrations allows controlling the surface coverage by gold.

Selective Electrooxidation of Glycerol Into Value-Added Chemicals: A Short Overview.

A comprehensive overview of the catalysts developed for the electrooxidation of glycerol with the aim of producing selectively value-added compounds is proposed in the present contribution. By presenting the main results reported in the literature on glycerol electrooxidation in acidic and alkaline media, using different kinds of catalytic materials (monometallic catalysts based on platinum group metals and non-noble metals, multimetallic alloys, or modification of surfaces by adatoms, etc.) and under different experimental conditions, some general trends concerning the effects of catalyst composition and structure, of reaction medium and of the electrode potential to enhance the activity for the glycerol oxidation reaction and of the selectivity toward a unique value-added product will be presented and discussed.

Interfacial structure of atomically flat polycrystalline Pt electrodes and modified Sauerbrey equation.

The electrochemical quartz-crystal nanobalance (EQCN) measures in situ mass changes associated with interfacial electrode processes. Real electrodes are not atomically flat, thus their surface roughness affects the conversion of frequency variations (Δf) to mass changes (Δm) associated with electrochemical processes. Here, we analyze Δm associated with the electrochemical H adsorption/desorption and surface oxide formation/reduction on Pt electrodes of gradually increasing surface roughness using the EQCN and cyclic-voltammetry in an aqueous HSO solution.

Octahedral palladium nanoparticles as excellent hosts for electrochemically adsorbed and absorbed hydrogen.

We report new results for electrochemical H adsorption on and absorption in octahedral palladium nanoparticles (Pd-NPs) with an average tip-to-tip size of 7.8 nm and a narrow size distribution. They reveal a very high H loading of 0.

Electrochemical behavior of unsupported shaped palladium nanoparticles.

The potential range in which hydrogen electro-adsorption, electro-absorption, and evolution reaction occur is examined in an acidic medium using cyclic-voltammetry (CV) and Pd nanoparticles with controlled size and shape distributions. The three processes give rise to unique features in CV profiles and are observed in distinct potential ranges. This behavior is not observed for bulk Pd materials and arises due to the nanoscopic nature of the Pd materials.

Self-supported Pd(x)Bi catalysts for the electrooxidation of glycerol in alkaline media.

Highly active self-supported PdxBi catalysts are synthesized by the sacrificial support method. Self-supported PdxBi catalysts have a porous nanostructured morphology with high surface areas (in the range from 75 to 100 m(2) g(-1)), making PdxBi a state-of-the-art catalyst. Pd4Bi displays the highest activity toward glycerol oxidation.

One-step synthesis and chemical characterization of Pt-C nanowire composites by plasma sputtering.

Plasma increases activity: A one-step synthesis of Pt-C nanowire composites using a plasma co-deposition method is reported. Electrodes with a very low Pt loading can be obtained. Pt particles with sizes ranging from 1 to 2 nm are decorating the columnar carbon nanostructures because of strong interactions.

Pt particles functionalized on the molecular level as new nanocomposite materials for electrocatalysis.

A nanocomposite material consisting of platinum nanoparticles surrounded by an ionic conducting polymer dispersed on carbon Vulcan XC72 was synthesized. The aim of this nanocomposite material is to translate the triple-phase boundary to a molecular level in electrochemical systems involving a polymer electrolyte. The ionic conducting polymer is a poly(styrenesulfonic acid) (PSSA, or PSSNa in its sodium form) synthesized by atom-transfer radical polymerization.

Electrochemical valorisation of glycerol.

The worldwide glycerol stocks are increasing; to make the biodiesel industry sustainable economically, this chemical could be used as a secondary primary raw material. Electric energy or hydrogen and added-value-chemical cogeneration becomes more and more an important research topic for increasing economical and industrial interests towards electrochemical technologies. Studies on glycerol electrooxidation for fuel or electrolysis cell applications are scarce.

Evidence of an Eley-Rideal mechanism in the stripping of a saturation layer of chemisorbed CO on platinum nanoparticles.

The oxidative stripping of a saturation layer of CO(chem) was studied on platinum nanoparticles of high shape selectivity and narrow size distribution. Nanospheres, nanocubes, and nano-octahedrons were synthesized using the water-in-oil microemulsion or polyacrylate methods. The three shapes allowed examination of the CO(chem) stripping in relation to the geometry of the nanoparticles and presence of specific nanoscopic surface domains.

Electro-oxidation of CO(chem) on Pt nanosurfaces: solution of the peak multiplicity puzzle.

An understanding of the oxidation of chemisorbed CO (CO(chem)) on Pt nanoparticle surfaces is of major importance to fuel cell technology. Here, we report on the relation between Pt nanoparticle surface structure and CO(chem) oxidative stripping behavior. Oxidative stripping voltammograms are obtained for CO(chem) preadsorbed on cubic, octahedral, and cuboctahedral Pt nanoparticles that possess preferentially oriented and atomically flat domains.

Insights into the effects of functional groups on carbon nanotubes for the electrooxidation of methanol.

Functionalized carbon nanotubes were used as a support for PtCo nanoparticles. Their performance as electrocatalysts for the electrooxidation of methanol was evaluated by cyclic voltammetry and in situ FTIR reflectance spectroscopy. The onset potentials for both the electrooxidation of methanol and the production of CO(2) shifted to less positive values for catalysts prepared with more oxygen groups on the support.

Modification of carbon substrates by aryl and alkynyl iodonium salt reduction.

Different carbon materials were modified using iodonium ion reduction creating radicals, which after reaction with carbon surfaces formed grafted layers of molecules. Several molecules (4-bromophenyl, 4-fluorophenyl, 6-chlorohexyne, and 4-bromobutyne) were grafted on glassy carbon and Vulcan XC72 carbon substrates. Carbon substrates were shown to be free of halogen atoms; therefore, the quantification of the grafted groups containing halogen atoms was facilitated.

Improvement of the platinum nanoparticles-carbon substrate interaction by insertion of a thiophenol molecular bridge.

The effect of thiophenol layer grafted on carbon for platinum catalyst stabilization was studied. The grafted layer was prepared by reduction of 4-thiophenoldiazonium ions in the presence of Vulcan XC72 substrate. The grafted layer was characterized by elemental analysis, thermogravimetric analysis coupled with mass spectrometry, and X-ray photoelectron spectroscopy.

Electrochemical derivatization of carbon surface by reduction of in situ generated diazonium cations.

The derivatization of a glassy carbon electrode surface was achieved by electrochemical reduction of several in situ generated diazonium cations. The diazonium cations were synthesized in the electrochemical cell by reaction of the corresponding amines with NaNO2 in aqueous HCl. The versatility of the method was demonstrated by using six diazonium cations.