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Nanomaterials based on Pd nanoparticles supported on Vulcan carbon (XC-72R) were prepared by the organometallic approach in one-pot and mild conditions (3 bar hydrogen and room temperature) using Pd(dba)2 (bis (dibenzylideneacetone) palladium (0)) as metal source and hexadecylamine (HDA) as stabilizer. High-resolution transmission electron microscopy (HR-TEM) evidenced the presence of well-dispersed Pd nanoparticles of ca. 4.5 nm mean size onto the carbon support (Pd/HDA/C). Scanning and transmission electron microscopy with electron energy loss spectroscopy (STEM-EELS) allowed to determine the chemical composition of the nanomaterials. When the Pd/HDA/C nanomaterial was submitted to heating treatment (ht) at 400 °C under air (referred as Pd/HDA/C@air-ht), X-ray photoelectron spectroscopy (XPS) and HR-TEM/STEM-EELS analyses suggested the presence of interactions between PdO and Pd(0) as a result of the formation of Pd@PdO core–shell nanoparticles. The highest oxidation current magnitude during methanol oxidation reaction is ascribed to the heat-treated material, linked with a better electron and mass transfer processes at the electrode interface. This can be attributed to electronic interactions at the core–shell formed, which might promote different redox processes at the electrode interface during CH3OH deprotonation in the alkaline electrolyte. [ABSTRACT FROM AUTHOR]

The synthesis of Rh nanoparticles has been performed through an organometallic approach starting from the tris(allyl) rhodium complex, Rh(η3-C3H5)3, as precursor and using an alcohol as both a solvent and a stabilizer, under mild reaction conditions (room temperature; 3 bar H2). The influence of the alcohol used, among methanol, propanol or heptanol, on the morphological and structural characteristics as well as on the magnetic and electrocatalytic properties of the obtained Rh nanoparticles has been investigated. Assemblies of Rh nanoparticles of various sizes have been observed depending on the alkyl chain length of the alcohol used. A noticeable effect of the nanostructured character of these Rh nanoparticles is the appearance of a ferromagnetic ordering at room temperature due to a modified electronic structure. Magnetic moments per atom were determined as follows: 0.099, 0.073 and 0.036 µB for methanol, heptanol and propanol, respectively. The electrochemical evaluation of these Rh nanoparticles on the oxygen reduction reaction (ORR) showed that the electroactivity depends on the chain length of the alcohol; thus, Rh-heptanol system displayed the highest electroactivity for ORR. [ABSTRACT FROM AUTHOR]

The reactivity of ruthenium nanoparticles stabilized by 4-(3-phenylpropyl)pyridine in hydrogen transfer and hydrogenation processes was monitored by NMR spectroscopy. Unsaturated substrates such as styrene, 4-vinylpyridine and 4-phenyl-but-3-en-2-one were used as model molecules to investigate the surface properties of nanoparticles by a combination of NMR studies. Interestingly, the hydrides present at the metallic surface after nanoparticles synthesis are selectively transferred to vinylic groups without reducing the aromatic rings, under dihydrogen-free atmosphere. DOSY and NOE NMR experiments permitted to propose a way of interaction of the organic compounds at the metallic surface. In particular, the coordination of the substrate could be evidenced for 4-vinylpyridine and 4-ethylpyridine but not for styrene derivatives. Graphical Abstract: Curved double arrows represent magnetization exchanges. Straight arrows represent adsorption/desorption phenomena. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]