Reducing the thermal deformation of InSb crystal by using double-bounce HHRMs in the TPS tender X-ray absorption spectroscopy beamline.

The Taiwan Photon Source (TPS) with high brightness and energy tunability is suitable for applications in spectroscopy. The tender X-ray absorption beamline will be optimized for X-ray absorption spectroscopy measurements using a bending-magnet source in a unique photon energy range (1.7-10 keV) and two crystal pairs [InSb(111) and Si(111)] separated using back-to-back double-crystal monochromators (DCMs).

Kinetically controlled autocatalytic chemical process for bulk production of bimetallic core-shell structured nanoparticles.

Although bimetallic core@shell structured nanoparticles (NPs) are achieving prominence due to their multifunctionalities and exceptional catalytic, magnetic, thermal, and optical properties, the rationale underlying their design remains unclear. Here we report a kinetically controlled autocatalytic chemical process, adaptable for use as a general protocol for the fabrication of bimetallic core@shell structured NPs, in which a sacrificial Cu ultrathin layer is autocatalytically deposited on a dimensionally stable noble-metal core under kinetically controlled conditions, which is then displaced to form an active ultrathin metal-layered shell by redox-transmetalation. Unlike thermodynamically controlled under-potential deposition processes, this general strategy allows for the scaling-up of production of high-quality core-shell structured NPs, without the need for any additional reducing agents and/or electrochemical treatments, some examples being Pd@Pt, Pt@Pd, Ir@Pt, and Ir@Pd.

Relating structural aspects of bimetallic Pt(3)Cr(1)/C nanoparticles to their electrocatalytic activity, stability, and selectivity in the oxygen reduction reaction.

Two methods were used to prepare bimetallic Pt(3)Cr(1)/C nanocatalysts with similar composition but different alloying extent (structure). We investigated how these differences in alloying extent affect the catalytic activity, stability and selectivity in the oxygen reduction reaction (ORR). One method, based on slow thermal decomposition of the Cr precursor at a rate that matches that of chemical reduction of the Pt precursor, allows fine control of the composition of the Pt(3)Cr(1)/C alloy, whereas the second approach, using the ethylene glycol method, results in considerable deviation (>25 %) from the projected composition.

CO-assisted synthesis of finely size-controlled platinum nanoparticles.

We present a surfactant-free approach for synthesizing size-dependent carbon supported Pt nanoparticles with mean sizes ranging from 4.8 to 1.7 nm by increasing ratios of CO/Ar.

Structural and electronic effects of carbon-supported Pt(x)Pd(1-x) nanoparticles on the electrocatalytic activity of the oxygen-reduction reaction and on methanol tolerance.

We report a systematic investigation on the structural and electronic effects of carbon-supported Pt(x)Pd(1-x) bimetallic nanoparticles on the oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) in acid electrolyte. Pt(x)Pd(1-x)/C nanocatalysts with various Pt/Pd atomic ratios (x=0.25, 0.

Chemical dealloying mechanism of bimetallic Pt-Co nanoparticles and enhancement of catalytic activity toward oxygen reduction.

The chemical dealloying mechanism of bimetallic Pt-Co nanoparticles (NPs) and enhancement of their electrocatalytic activity towards the oxygen reduction reaction (ORR) have been investigated on a fundamental level by the combination of X-ray absorption spectroscopy (XAS) and aberration-corrected scanning transmission electron microscopy (STEM). Structural parameters, such as coordination numbers, alloy extent, and the unfilled d states of Pt atoms, are derived from the XAS spectra, together with the compositional variation analyzed by line-scanning energy-dispersive X-ray spectroscopy (EDX) on an atomic scale, to gain new insights into the dealloying process of bimetallic Pt-Co NPs. The XAS results on acid-treated Pt-Co/C NPs reveal that the Co-Co bonding in the bimetallic NPs dissolves first and the remaining morphology gradually transforms to a Pt-skin structure.

A dedicated small-angle X-ray scattering beamline with a superconducting wiggler source at the NSRRC.

At the National Synchrotron Radiation Research Center (NSRRC), which operates a 1.5 GeV storage ring, a dedicated small-angle X-ray scattering (SAXS) beamline has been installed with an in-achromat superconducting wiggler insertion device of peak magnetic field 3.1 T.

Architecture of Pd-Au bimetallic nanoparticles in sodium bis(2-ethylhexyl)sulfosuccinate reverse micelles as investigated by X-ray absorption spectroscopy.

In this study, we demonstrate the unique application of X-ray absorption spectroscopy (XAS) as a fundamental characterization tool to help in designing and controlling the architecture of Pd-Au bimetallic nanoparticles within a water-in-oil microemulsion system of water/sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/n-heptane. Structural insights obtained from the in situ XAS measurements recorded at each step during the formation process revealed that Pd-Au bimetallic clusters with various Pd-Au atomic stackings are formed by properly performing hydrazine reduction and redox transmetalation reactions sequentially within water-in-oil microemulsions. A structural model is provided to explain reasonably each reaction step and to give detailed insight into the nucleation and growth mechanism of Pd-Au bimetallic clusters.

X-ray beamlines for structural studies at the NSRRC superconducting wavelength shifter.

Using a superconducting-wavelength-shifter X-ray source with a photon flux density of 10(11)-10(13) photons s(-1) mrad(-1) (0.1% bandwidth)(-1) (200 mA)(-1) in the energy range 5-35 keV, three hard X-ray beamlines, BL01A, BL01B and BL01C, have been designed and constructed at the 1.5 GeV storage ring of the National Synchrotron Radiation Research Center (NSRRC).

Heat-induced alterations in the surface population of metal sites in bimetallic nanoparticles.

The ability to alter the surface population of metal sites in bimetallic nanoparticles (NPs) is of great interest in the context of heterogeneous catalysis. Here, we report findings of surface alterations of Pt and Ru metallic sites in bimetallic carbon-supported (PtRu/C) NPs that were induced by employing a controlled thermal-treatment strategy. The thermal-treatment procedure was designed in such a way that the particle size of the initial NPs was not altered and only the surface population of Pt and Ru was changed, thus allowing us to deduce structural information independent of particle-size effects.

Formation of Pt-Ru nanoparticles in ethylene glycol solution: an in situ X-ray absorption spectroscopy study.

The chemical state and formation mechanism of Pt-Ru nanoparticles (NPs) synthesized by using ethylene glycol (EG) as a reducing agent and their stability have been examined by in situ X-ray absorption spectroscopy (XAS) at the Pt LIII and Ru K edges. It appears that the reduction of Pt(IV) and Ru(III) precursor salts by EG is not a straightforward reaction but involves different intermediate steps. The pH control of the reaction mixture containing Pt(IV) and Ru(III) precursor salts in EG to 11 led to the reduction of Pt(IV) to Pt(II) corresponding to [PtCl4](2-) whereas Ru(III)Cl3 is changed to the [Ru(OH)6](3-) species.

Nucleation and growth mechanism of Pd/Pt bimetallic clusters in sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles as studied by in situ X-ray absorption spectroscopy.

We report in situ X-ray absorption spectroscopy (XAS) investigations on the formation of palladium-platinum (Pd/Pt) bimetallic clusters at the early stage within the water-in-oil microemulsion system of water/AOT/n-heptane. The reduction of palladium and platinum ions and the formation of corresponding clusters are monitored as a function of dosage of reducing agent, hydrazine (N(2)H(5)OH). Upon successive addition of the reducing agent, hydrazine (N(2)H(5)OH), five distinguishable steps are observed in the formation process of Pd/Pt clusters at the early stage.

Probing the formation mechanism and chemical states of carbon-supported Pt-Ru nanoparticles by in situ X-ray absorption spectroscopy.

The understanding of the formation mechanism of nanoparticles is essential for the successful particle design and scaling-up process. This paper reports findings of an X-ray absorption spectroscopy (XAS) investigation, comprised of X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) regions, to understand the mechanism of the carbon-supported Pt-Ru nanoparticles (NPs) formation process. We have utilized Watanabe's colloidal reduction method to synthesize Pt-Ru/C NPs.

Structural models and atomic distribution of bimetallic nanoparticles as investigated by X-ray absorption spectroscopy.

In this report, we describe a general methodology to determine the extent of alloying or atomic distribution quantitatively in bimetallic nanoparticles (NPs) by X-ray absorption spectroscopy (XAS). The structural parameters determined in these studies serve as a quantitative index and provide a general route to determine the structural aspects of the bimetallic NPs. We have derived various types of possible structural models based on the extent of alloying and coordination number parameters of bimetallic NPs.