Hirokazu Kobayashi

We have investigated the hydrogen absorption/desorption hysteresis by means of in situ powder X-ray diffraction (XRD) and solid-state 2H NMR to clarify the location of hydrogen, surface or body, and its chemical form, molecular, atomic, or as hydride. The present results point out that strongly trapped hydrogen atoms exist inside the Pd nanoparticles due to a strong Pd−H bond formation and are stabilized in the lattice of Pd nanoparticles, compared to bulk Pd.

We have achieved the creation of a solid-solution alloy where Pd and Pt are homogeneously mixed at the atomic level, by a process of hydrogen absorption/desorption as a trigger for core (Pd)/shell (Pt) nanoparticles. The structural change from core/shell to solid solution has been confirmed by in situ powder X-ray diffraction, energy dispersive spectra, solid-state (2)H NMR measurement, and hydrogen pressure-composition isotherms. The successfully obtained Pd-Pt solid-solution nanoparticles with

We report novel PtW solid-solution nanoparticles (NPs) produced through electrochemical cleaning of core/shell PtW@WO₃ NPs. The resulting PtW NPs achieved a record hydrogen evolution reaction (HER) performance as a class of Pt-based solid-solution alloys. A current density of 10 mA cm^-2 was reached with an overpotential of 19.4 mV, which is significantly lower than that of a commercial Pt catalyst (26.3 mV). The PtW NPs also exhibited long-term stability. Theoretical calcul

We have investigated the hydrogen absorption behavior of Pd/Pt nanoparticles with a core/shell-type structure. From the results of the hydrogen pressure−composition (PC) isotherm and solid-state 2H NMR measurements, it was revealed that the Pd/Pt nanoparticles can absorb hydrogen, and most of the absorbed hydrogen atoms are situated around the interfacial region between the Pd core and the Pt shell of the Pd/Pt nanoparticles, indicating that the core/shell boundary plays an important role in the

Currently 118 known elements are represented in the periodic table. Of these 118 elements, only about 80 elements are stable, nonradioactive, and widely available for our society. From the viewpoint of the "elements strategy", we need to make full use of the 80 elements to bring out their latent ability and create innovative materials. Furthermore, there is a strong demand that the use of rare or toxic elements be reduced or replaced while their important properties are retained. Advanced scienc

We report the synthesis and characterization of highly active Cu nanoparticles covered with zirconium/hafnium-based metal-organic frameworks for CO₂ hydrogenation to methanol. Compared to <b>Cu/γ-Al₂O₃</b> , <b>Cu/ZIF-8</b>, <b>Cu/MIL-100</b> and <b>Cu/UiO-66</b> composites, UiO-66 acts as the most active support, with <b>Cu/Zr-UiO-66</b> producing methanol at a rate 70 times higher than that of <b>Cu/γ-Al₂O₃</b> . In addition, the replaceme

We propose and demonstrate a novel 1.3 μm InGaAsP/InGaAsP multiple-quantum-well (MQW) BH Fabry-Perot laser diode monolithically integrated with a MQW tapered thickness waveguide. A selective area growth (SAG) technique is used to fabricate the tapered thickness waveguide with low absorption loss and to integrate it with the MQW gain region with a high coupling efficiency. We achieve very narrow vertical and lateral far-field FWHM of 11.8/spl deg/ and 8.0/spl deg/, with low threshold current of 1

Hybrid materials composed of metal nanoparticles and metal-organic frameworks (MOFs) have attracted much attention in many applications, such as enhanced gas storage and catalytic, magnetic, and optical properties, because of the synergetic effects between the metal nanoparticles and MOFs. In this Forum Article, we describe our recent progress on novel synthetic methods to produce metal nanoparticles covered with a MOF (metal@MOF). We first present Pd@copper(II) 1,3,5-benzenetricarboxylate (HKUS

We demonstrate a novel, simple synthetic method for metal (Ni) NPs in a MOF using the partial thermal decomposition of nickel(II) 2,5-dihydroxyterephthalate (Ni-MOF-74). The Ni NPs inside the Ni-MOF-74 are several nanometers in size, and the size can be precisely controlled by the heating conditions.

Ru is an important catalyst in many types of reactions. Specifically, Ru is well known as the best monometallic catalyst for oxidation of carbon monoxide (CO) and has been practically used in residential fuel cell systems. However, Ru is a minor metal, and the supply risk often causes violent fluctuations in the price of Ru. Performance-improved and cost-reduced solid-solution alloy nanoparticles of the Cu-Ru system for CO oxidation are now presented. Over the whole composition range, all of the

Size-controlled atomic-level Pd-Au alloy nanoparticles have been synthesized with a wide range of atomic ratios by a facile method using H2 gas, and their controllable hydrogen-absorption properties have been studied from hydrogen pressure-composition isotherms and solid-state 2H NMR spectra.

We report the first example of nanosize-induced hydrogen storage in a metal that does not absorb hydrogen in its bulk form. Rhodium particles with diameters of <10 nm were found to exhibit hydrogen-storage capability, while bulk Rh does not absorb hydrogen. Hydrogen storage was confirmed by in situ powder X-ray diffraction, solid-state (2)H NMR, and hydrogen pressure-composition isotherm measurements. The hydrogen absorption capacity could be tuned by controlling the particle size.

We report on Cu/amUiO-66, a composite made of Cu nanoparticles (NPs) and amorphous [Zr₆ O₄ (OH)₄ (BDC)₆ ] (amUiO-66, BDC=1,4-benzenedicarboxylate), and Cu-ZnO/amUiO-66 made of Cu-ZnO nanocomposites and amUiO-66. Both structures were obtained via a spray-drying method and characterized using high-resolution transmission electron microscopy, energy dispersive spectra, powder X-ray diffraction and extended X-ray absorption fine structure. The catalytic ac

We have synthesized and characterized homogeneous solid-solution alloy nanoparticles of Pd and Rh, which are immiscible with each other in the equilibrium bulk state at around room temperature. The Pd-Rh alloy nanoparticles can absorb hydrogen at ambient pressure and the hydrogen pressure of Pd-Rh alloys for hydrogen storage is dramatically decreased by more than 4 orders of magnitude from the corresponding pressure in the metastable bulk state. The solid-solution state is still maintained in th

We report nanosize-induced hydrogen storage in Ir, which does not absorb hydrogen in its bulk form. The mean diameter of the obtained Ir nanoparticles was estimated as 1.5 ± 0.5 nm by transmission electron microscopy. Hydrogen storage was confirmed by solid-state (2)H NMR and hydrogen pressure-composition isotherm measurements.