Search

Surface engineering is known as an effective strategy to enhance the catalytic properties of Pt-based nanomaterials. Herein, we report on surface engineering Ni-Pt nanoalloys with a facile method by varying the Ni doping concentration and oleylamine/oleicacid surfactant-mix. The alloy-composition, exposed facet condition, and surface lattice strain are, thereby manipulated to optimize the catalytic efficiency of such nanoalloys for methanol oxidation reaction (MOR). Exemplary nanoalloys including Ni0.69Pt0.31 truncated octahedrons, Ni0.45Pt0.55 nanomultipods and Ni0.20Pt0.80 nanoflowers are thoroughly characterized, with a commercial Pt/C catalyst as a common benchmark. Their variations in MOR catalytic efficiency are significant: 2.2 A/mgPt for Ni0.20Pt0.80 nanoflowers, 1.2 A/mgPt for Ni0.45Pt0.55 nanomultipods, 0.7 A/mgPt for Ni0.69Pt0.31 truncated octahedrons, and 0.6 A/mgPt for the commercial Pt/C catalysts. Assisted by density functional theory calculations, we correlate these observed catalysis-variations particularly to the intriguing presence of surface interplanar-strains, such as {111} facets with an interplanar-tensile-strain of 2.6% and {200} facets with an interplanar-tensile-strain of 3.5%, on the Ni0.20Pt0.80 nanoflowers. [ABSTRACT FROM AUTHOR]

A simple yet general one-step solvothermal method is applied to synthesize sub-7 nm monodispersed single-crystal NiPt nanoparticles (NPs) with the morphology of truncated octahedrons in the alloying state of disordered atomic arrangements. The effective magnetic moments of these NPs exhibit an anomalous temperature dependency, increasing from approximately 0.9 μ/atom at 15 K to 1.9 μ/atom at 300 K. This is an increase by a factor of more than three compared with bulk Ni. On the basis of experiments involving X-ray absorption near-edge spectroscopy of the L3 edge for Pt and density functional theory calculations, the observed novel magnetism enhancement and its anomalous temperature dependence are attributed to the electron transfer arising from the thermal-activation effects. [ABSTRACT FROM AUTHOR]

We present a facile and controllable method for the large-scale fabrication of highly-ordered octahedral FeO colloidal 'single crystals' without the assistance of a substrate. Oleic acid is used to reduce the solubility of the nano-building blocks in colloidal solution and to induce a 'crystallization' process. Our colloidal crystals are of multimicron size and show typical crystallographic characteristics. They have a very robust structure and can serve as a novel ordered magnetic mesoporous material with a relatively narrow pore size distribution. The sample possesses an extremely high Verwey transition temperature ( T) of 100 K and a high saturation magnetization ( M) of 86 emu/g at 5 K based on its good crystallinity, as well as the interparticle dipolar interaction behavior arising from its unique structure. Electrochemical measurements have demonstrated the excellent capacity of the mesoporous colloidal crystals when used in lithium-ion batteries. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Polycrystalline magnetite hollow spheres with diameter of about 200 nm and shell thickness of 30-60 nm were prepared via a facile solution route. For the reaction, ethylene glycol (EG) served as the reducing agent and soldium acetate played the role of precipitator. In addition, polyvinylpyrrolidone (PVP) served as a surface stabilizer. The morphologies and structures were characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The intermediate products at different stages were also studied to shed light on the evolution of phase formation. It revealed that the hollow structure formed via self-assembly of nanocrystallites (about 15 nm) using sodium acetate as mild precipitator. Evidences further pointed out that the Ostwald ripening process well explained the growth mechanism of the hollow structure. Magnetization measurements showed that the coercivity of magnetite hollow spheres at low temperature is about 200 Oe and the saturation magnetization is about 83 emu g, roughly 85% that of the bulk phase, close to the value of its solid counterpart. In addition, a freezing transition was observed at 25 K. [ABSTRACT FROM AUTHOR]

Demonstrates that high pressure chemical vapor deposition (HPCVD) is an effective and efficient approach to the synthesis of thick magnesium boride films over the stainless substrate. X-ray diffraction pattern of magnesium boride film grown on the stainless steel substrate; Deposition rate of the film; Tenacity and the bonding strength of the film to the substrate.