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排序方式: 共有285条查询结果,搜索用时 15 毫秒
41.
42.
Bo Huang Hirokazu Kobayashi Tomokazu Yamamoto Takaaki Toriyama Syo Matsumura Yoshihide Nishida Katsutoshi Sato Katsutoshi Nagaoka Masaaki Haneda Wei Xie Yusuke Nanba Michihisa Koyama Fenglong Wang Shogo Kawaguchi Yoshiki Kubota Hiroshi Kitagawa 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(8):2252-2257
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 CuxRu1?x nanoparticles exhibit significantly enhanced CO oxidation activities, even at 70 at % of inexpensive Cu, compared to Ru nanoparticles. Only 5 at % replacement of Ru with Cu provided much better CO oxidation activity, and the maximum activity was achieved by 20 at % replacement of Ru by Cu. The origin of the high catalytic performance was found as CO site change by Cu substitution, which was investigated using in situ Fourier transform infrared spectra and theoretical calculations. 相似文献
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44.
Dongshuang Wu Kohei Kusada Tomokazu Yamamoto Takaaki Toriyama Syo Matsumura Ibrahima Gueye Okkyun Seo Jaemyung Kim Satoshi Hiroi Osami Sakata Shogo Kawaguchi Yoshiki Kubota Hiroshi Kitagawa 《Chemical science》2020,11(47):12731
We report the synthesis of high-entropy-alloy (HEA) nanoparticles (NPs) consisting of five platinum group metals (Ru, Rh, Pd, Ir and Pt) through a facile one-pot polyol process. We investigated the electronic structure of HEA NPs using hard X-ray photoelectron spectroscopy, which is the first direct observation of the electronic structure of HEA NPs. Significantly, the HEA NPs possessed a broad valence band spectrum without any obvious peaks. This implies that the HEA NPs have random atomic configurations leading to a variety of local electronic structures. We examined the hydrogen evolution reaction (HER) and observed a remarkably high HER activity on HEA NPs. At an overpotential of 25 mV, the turnover frequencies of HEA NPs were 9.5 and 7.8 times higher than those of a commercial Pt catalyst in 0.05 M H2SO4 and 1.0 M KOH electrolytes, respectively. Moreover, the HEA NPs showed almost no loss during a cycling test and were much more stable than the commercial Pt catalyst. Our findings on HEA NPs may provide a new paradigm for the design of catalysts.RuRhPdIrPt high-entropy-alloy nanoparticles with a broad and featureless valence band spectrum show high hydrogen evolution reaction activity. 相似文献
45.
46.
The Electronic State of Hydrogen in the α Phase of the Hydrogen‐Storage Material PdH(D)x: Does a Chemical Bond Between Palladium and Hydrogen Exist? 下载免费PDF全文
Shun Dekura Prof. Hirokazu Kobayashi Prof. Ryuichi Ikeda Prof. Mitsuhiko Maesato Haruka Yoshino Prof. Masaaki Ohba Prof. Takayoshi Ishimoto Dr. Shogo Kawaguchi Prof. Yoshiki Kubota Dr. Satoru Yoshioka Prof. Syo Matsumura Prof. Takeharu Sugiyama Prof. Hiroshi Kitagawa 《Angewandte Chemie (International ed. in English)》2018,57(31):9823-9827
The palladium–hydrogen system is one of the most famous hydrogen‐storage systems. Although there has been much research on β‐phase PdH(D)x, we comprehensively investigated the nature of the interaction between Pd and H(D) in α‐phase PdH(D)x (x<0.03 at 303 K), and revealed the existence of Pd?H(D) chemical bond for the first time, by various in situ experimental techniques and first‐principles theoretical calculations. The lattice expansion, magnetic susceptibility, and electrical resistivity all provide evidence. In situ solid‐state 1H and 2H NMR spectroscopy and first‐principles theoretical calculations revealed that a Pd?H(D) chemical bond exists in the α phase, but the bonding character of the Pd?H(D) bond in the α phase is quite different from that in the β phase; the nature of the Pd?H(D) bond in the α phase is a localized covalent bond whereas that in the β phase is a metallic bond. 相似文献
47.
Mozer AJ Wagner P Officer DL Wallace GG Campbell WM Miyashita M Sunahara K Mori S 《Chemical communications (Cambridge, England)》2008,(39):4741-4743
Electron lifetime and diffusion coefficient measurements in highly efficient porphyrin-sensitised TiO(2) solar cells showed reduced electron lifetime, and consequently, lower photo-induced electron density under illumination compared to commonly used ruthenium dye (N719)-sensitised solar cells, which is proposed to be the origin of the generally lower open circuit voltage. 相似文献
48.
Toshiaki Yoshioka Tomohito Kameda Shogo Imai Akitsugu Okuwaki 《Polymer Degradation and Stability》2008,93(6):1138-1141
A solution of NaOH dissolved in ethylene glycol (EG) was effective in the dechlorination of poly(vinyl chloride) (PVC) at atmospheric pressure. The degree of dechlorination increased with increasing temperature, reaching a maximum of 97.8% at 190 °C. The dechlorination proceeded under chemical control and exhibited first-order kinetics with an apparent activation energy of 170 kJ mol−1. The apparent rate constant for dechlorination in 1.0 M NaOH/EG was approximately 150 times greater than that in 1.0 M NaOH/H2O. In addition, dechlorination was faster at atmospheric pressure in NaOH/EG than under high pressure in NaOH/H2O. The dechlorination reaction occurs via a combination of E2 and SN2 mechanisms. 相似文献
49.
Fukushima T Arai K Tomiya M Mitsuhashi S Sasaki T Santa T Imai K Toyo'oka T 《Biomedical chromatography : BMC》2008,22(1):100-105
N-acetyl-L-aspartic acid (NAA) is an endogenous compound, and its brain concentration is suggested to be altered in neurological disorders. In the present study, a fluorescence determination method for NAA was developed by employing reversed-phase high-performance liquid chromatography (HPLC) with pre-column fluorescence derivatization using 4-N,N-dimethylaminosulfonyl-7-N-(2-aminoethyl)amino-2,1,3-benzoxadiazole (DBD-ED). Using methylsuccinic acid as the internal standard, a linear calibration curve for NAA was constructed in the range 125-1000 microM (n=3). The detection limit on the column was approximately 5.0 fmol (signal-to-noise ratio 3). The proposed HPLC method was applied to determine NAA in the rat cerebrum homogenate. Cerebrum NAA was successfully determined using 10 microL of the homogenate, and the validation data for the proposed HPLC method demonstrated satisfactory results. Intra- and inter-day precision and accuracy were within 1.1-7.0 and -8.1-6.3%, respectively. The concentration of NAA in the male rat cerebrum (13 weeks old) was 84+/-4.6 micromol/mg protein (n=3). 相似文献
50.
Taichi Mitsumoto Dr. Yuya Ashida Dr. Kazuya Arashiba Dr. Shogo Kuriyama Akihito Egi Prof. Dr. Hiromasa Tanaka Prof. Dr. Kazunari Yoshizawa Prof. Dr. Yoshiaki Nishibayashi 《Angewandte Chemie (International ed. in English)》2023,62(43):e202306631
We newly designed and prepared a novel molybdenum complex bearing a 4-[3,5-bis(trifluoromethyl)phenyl]pyridine-based PNP-type pincer ligand, based on the bond dissociation free energies (BDFEs) of the N−H bonds in molybdenum-imide complexes bearing various substituted pyridine-based PNP-type pincer ligands. The complex worked as an excellent catalyst toward ammonia formation from the reaction of an atmospheric pressure of dinitrogen with samarium diiodide as a reductant and water as a proton source under ambient reaction conditions, where up to 3580 equivalents of ammonia were formed based on the molybdenum atom of the catalyst. The catalytic activity was significantly improved by one order of magnitude larger than that observed when using the complex before modification. 相似文献