共查询到20条相似文献,搜索用时 15 毫秒
1.
Dr. Guozhu Chen Dr. Stefano Desinan Prof. Dr. Renzo Rosei Prof. Dr. Federico Rosei Prof. Dr. Dongling Ma 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(25):7925-7930
We report the synthesis and characterization of new NixRu1?x (x=0.56–0.74) alloy nanoparticles (NPs) and their catalytic activity for hydrogen release in the ammonia borane hydrolysis process. The alloy NPs were obtained by wet‐chemistry method using a rapid lithium triethylborohydride reduction of Ni2+ and Ru3+ precursors in oleylamine. The nature of each alloy sample was fully characterized by TEM, XRD, energy dispersive X‐ray spectroscopy (EDX), and X‐ray photoelectron spectroscopy (XPS). We found that the as‐prepared Ni–Ru alloy NPs exhibited exceptional catalytic activity for the ammonia borane hydrolysis reaction for hydrogen release. All Ni–Ru alloy NPs, and in particular the Ni0.74Ru0.26 sample, outperform the activity of similar size monometallic Ni and Ru NPs, and even of Ni@Ru core‐shell NPs. The hydrolysis activation energy for the Ni0.74Ru0.26 alloy catalyst was measured to be approximately 37 kJ mol?1. This value is considerably lower than the values measured for monometallic Ni (≈70 kJ mol?1) and Ru NPs (≈49 kJ mol?1), and for Ni@Ru (≈44 kJ mol?1), and is also lower than the values of most noble‐metal‐containing bimetallic NPs reported in the literature. Thus, a remarkable improvement of catalytic activity of Ru in the dehydrogenation of ammonia borane was obtained by alloying Ru with a Ni, which is a relatively cheap metal. 相似文献
2.
Dr. Gilles Alcaraz Dr. Sylviane Sabo‐Etienne 《Angewandte Chemie (International ed. in English)》2010,49(40):7170-7179
There have been a number of approaches developed for the catalyzed dehydrogenation of amine–boranes as potential dihydrogen sources for hydrogen storage applications in recent years. Key advances in this area have been recently made thanks to catalytic and stoichiometric studies. In this Minireview, the fate of amine–boranes upon coordination to a metal center is discussed with a particular emphasis on B? H activation pathways. We focus on the few cases in which coordination of the resulting dehydrogenated product could be achieved, which includes the coordination of aminoborane, the simplest unit resulting from dihydrogen release of ammonia–borane. 相似文献
3.
A facile impregnation method under mild condition is designed for synthesis of highly dispersed Pt nanoparticles with a narrow size of 4-7 nm on nitrogen-doped carbon nanotubes (CNx). CNx do not need any pre-surface modification due to the inherent chemical activity. The structure and nature of Pt/CNx were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive spectroscopy spectrum. All the experimental results revealed that the large amount of doped nitrogen atoms in CNx was virtually effective for capturing the Pt(IV) ions. The improved surface nitrogen functionalities and hydrophilicity contributed to the good dispersion and immobi- lization of Pt nanoparticles on the CNx surface. The Pt/CNx served as active and reusable catalysts in the hydrogenation of allyl alcohol. This could be attributed to high dispersion of Pt nanoparticles and stronger interaction between Pt and the supports, which prevented the Pt nanoparticles from aggregating into less active Pt black and from leaching as well. 相似文献
4.
Synthesis of Triple‐Layered Ag@Co@Ni Core–Shell Nanoparticles for the Catalytic Dehydrogenation of Ammonia Borane 下载免费PDF全文
Dr. Fangyuan Qiu Dr. Guang Liu Dr. Li Li Dr. Ying Wang Changchang Xu Dr. Cuihua An Chengcheng Chen Dr. Yanan Xu Yanan Huang Prof. Yijing Wang Prof. Lifang Jiao Prof. Huatang Yuan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(2):505-509
Triple‐layered Ag@Co@Ni core–shell nanoparticles (NPs) containing a silver core, a cobalt inner shell, and a nickel outer shell were formed by an in situ chemical reduction method. The thickness of the double shells varied with different cobalt and nickel contents. Ag0.04@Co0.48@Ni0.48 showed the most distinct core–shell structure. Compared with its bimetallic core–shell counterparts, this catalyst showed higher catalytic activity for the hydrolysis of NH3BH3 (AB). The synergetic interaction between Co and Ni in Ag0.04@Co0.48@Ni0.48 NPs may play a critical role in the enhanced catalytic activity. Furthermore, cobalt–nickel double shells surrounding the silver core in the special triple‐layered core–shell structure provided increasing amounts of active sites on the surface to facilitate the catalytic reaction. These promising catalysts may lead to applications for AB in the field of fuel cells. 相似文献
5.
Dr. Holger Helten Alasdair P. M. Robertson Prof. Dr. Anne Staubitz James R. Vance Dr. Mairi F. Haddow Prof. Dr. Ian Manners 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(15):4665-4680
The dehydrocoupling/dehydrogenation behavior of primary arylamine–borane adducts ArNH2 ? BH3 ( 3 a – c ; Ar= a : Ph, b : p‐MeOC6H4, c : p‐CF3C6H4) has been studied in detail both in solution at ambient temperature as well as in the solid state at ambient or elevated temperatures. The presence of a metal catalyst was found to be unnecessary for the release of H2. From reactions of 3 a , b in concentrated solutions in THF at 22 °C over 24 h cyclotriborazanes (ArNH‐BH2)3 ( 7 a , b ) were isolated as THF adducts, 7 a , b? THF, or solvent‐free 7 a , which could not be obtained via heating of 3 a – c in the melt. The μ‐(anilino)diborane [H2B(μ‐PhNH)(μ‐H)BH2] ( 4 a ) was observed in the reaction of 3 a with BH3?THF and was characterized in situ. The reaction of 3 a with PhNH2 ( 2 a ) was found to provide a new, convenient method for the preparation of dianilinoborane (PhNH)2BH ( 5 a ), which has potential generality. This observation, together with further studies of reactions of 4 a , 5 a , and 7 a , b , provided insight into the mechanism of the catalyst‐free ambient temperature dehydrocoupling of 3 a – c in solution. For example, the reaction of 4 a with 5 a yields 6 a and 7 a . It was found that borazines (ArN‐BH)3 ( 6 a – c ) are not simply formed via dehydrogenation of cyclotriborazanes 7 a – c in solution. The transformation of 7 a to 6 a is slowly induced by 5 a and proceeds via regeneration of 3 a . The adducts 3 a – c also underwent rapid dehydrocoupling in the solid state at elevated temperatures and even very slowly at ambient temperature. From aniline–borane derivative 3 c , the linear iminoborane oligomer (p‐CF3C6H4)N[BH‐NH(p‐CF3C6H4)]2 ( 11 ) was obtained. The single‐crystal X‐ray structures of 3 a – c , 5 a , 7 a , 7 b? THF, and 11 are discussed. 相似文献
6.
A Highly Effective Ruthenium System for the Catalyzed Dehydrogenative Cyclization of Amine–Boranes to Cyclic Boranes under Mild Conditions 下载免费PDF全文
Dr. Christopher J. Wallis Dr. Gilles Alcaraz Dr. Alban S. Petit Dr. Amalia I. Poblador‐Bahamonde Dr. Eric Clot Dr. Christian Bijani Dr. Laure Vendier Dr. Sylviane Sabo‐Etienne 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(37):13080-13090
We recently disclosed a new ruthenium‐catalyzed dehydrogenative cyclization process (CDC) of diamine–monoboranes leading to cyclic diaminoboranes. In the present study, the CDC reaction has been successfully extended to a larger number of diamine–monoboranes ( 4 – 7 ) and to one amine–borane alcohol precursor ( 8 ). The corresponding NB(H)N‐ and NB(H)O‐containing cyclic diaminoboranes ( 12 – 15 ) and oxazaborolidine ( 16 ) were obtained in good to high yields. Multiple substitution patterns on the starting amine–borane substrates were evaluated and the reaction was also performed with chiral substrates. Efforts have been spent to understand the mechanism of the ruthenium CDC process. In addition to a computational approach, a strategy enabling the kinetic discrimination on successive events of the catalytic process leading to the formation of the NB(H)N linkage was performed on the six‐carbon chain diamine–monoborane 21 and completed with a 15N NMR study. The long‐life bis‐σ‐borane ruthenium intermediate 23 possessing a reactive NHMe ending was characterized in situ and proved to catalyze the dehydrogenative cyclization of 1 , ascertaining that bis σ‐borane ruthenium complexes are key intermediates in the CDC process. 相似文献
7.
To design electrocatalysts with excellent performance, morphology, composition and structure is a decisive influential factor. In this work, ultrasmall Ag@Pd core‐shell nanocrystals supported on Vulcan XC72R carbon with different Ag/Pd atomic ratios are synthesized via a facile successive reduction approach with formaldehyde and ethylene glycol as reducing agents, respectively. The Ag‐core/Pd‐shell nanostructures are revealed by high‐resolution transmission electron microscopy (HRTEM). Ag@Pd core‐shell nanocrystals possess a narrow size distribution with an average size of ca. 4.3 nm. In comparison to monometallic Pd/C and commercial Pd black catalysts, such Ag@Pd core‐shell nanocrystals display excellent electrocatalytic activities for formic acid oxidation, which may be due to high Pd utilization derived from the formation of Ag@Pd core‐shell nanostructure and the strong interaction between Ag and Pd. 相似文献
8.
《化学:亚洲杂志》2017,12(8):860-867
Pd nanoparticles (NPs) supported on Ti‐doped graphitic carbon nitride (g‐C3N4) were synthesized by a deposition–precipitation route and a subsequent reduction with NaBH4. The features of the NPs were studied by XRD, TEM, FTIR, XPS, EXAFS and N2‐physisorption measurements. It was found that the NPs had an average size of 2.9 nm and presented a high dispersion on the surface of Ti‐doped g‐C3N4. Compared to Pd loaded on pristine g‐C3N4, the Pd NPs supported on Ti‐doped g‐C3N4 exhibited a high catalytic activity in formic acid dehydrogenation in water at room temperature. The enhanced activity could be attributed to the small Pd NPs size, as well as the strong interaction between Pd NPs and Ti‐doped g‐C3N4. 相似文献
9.
Synthesis of Size‐Controlled Ag@Co@Ni/Graphene Core–Shell Nanoparticles for the Catalytic Hydrolysis of Ammonia Borane 下载免费PDF全文
Fangyuan Qiu Li Li Guang Liu Changchang Xu Cuihua An Yanan Xu Ying Wang Yanan Huang Chengcheng Chen Prof. Yijing Wang Lifang Jiao Prof. Huatang Yuan 《化学:亚洲杂志》2014,9(2):487-493
Size‐controlled Ag0.04@Co0.48@Ni0.48 core–shell nanoparticles (NPs) were synthesized by employing graphene (rGO) with different reduction degrees as supports. The number of C?O and C? O functional groups on the surface of rGO might play a major role in controlling the particle size. The strong steric‐hindrance effect of C?O resulted in the growth of large particles, whereas C? O contributed to the formation of small particles. The particle size of Ag0.04@Co0.48@Ni0.48 NPs supported on rGO with different reduction degrees decreased as the number of C?O functional groups decreased. The decrease in the particle size probably led to the increase in the catalytic activity towards the hydrolysis of ammonia borane (AB). The enhanced catalytic activity largely stemmed from the increasing active sites on the surface of catalysts owing to the decreasing particle size. 相似文献
10.
Using a successive method, PAMAM dendrimer‐encapsulated bimetallic PdPt nanoparticles have been successfully prepared with core‐shell structures (Pd@Pt DENs). Evidenced by UV‐vis spectra, high resolution transmission electron microscopy, and X‐ray energy dispersive spectroscopy (EDS), the obtained Pd@Pt DENs are monodispersed and located inside the cavity of dendrimers, and they show a different structure from monometallic Pt or Pd and alloy PdPt DENs. The core‐shell structure of Pd@Pt DENs is further confirmed by infrared measurements with carbon monoxide (IR‐CO) probe. In order to prepare Pd@Pt DENs, a required Pd/Pt ratio of 1:2 is determined for the Pt shell to cover the Pd core completely. Finally, a mechanism for the formation of Pd@Pt DENs is proposed. 相似文献
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PC‐Activated Bimetallic Rhodium Xantphos Complexes: Formation and Catalytic Dehydrocoupling of Amine–Boranes 下载免费PDF全文
Dr. Heather C. Johnson Prof. Andrew S. Weller 《Angewandte Chemie (International ed. in English)》2015,54(35):10173-10177
{Rh(xantphos)}‐based phosphido dimers form by P? C activation of xantphos (4,5‐bis(diphenylphosphino)‐9,9‐dimethylxanthene) in the presence of amine–boranes. These dimers are active dehydrocoupling catalysts, forming polymeric [H2BNMeH]n from H3B?NMeH2 and dimeric [H2BNMe2]2 from H3B?NMe2H at low catalyst loadings (0.1 mol %). Mechanistic investigations support a dimeric active species, suggesting that bimetallic catalysis may be possible in amine–borane dehydropolymerization. 相似文献
13.
Frédéric Pelletier Dr. Diana Ciuculescu Jean‐Gabriel Mattei Dr. Pierre Lecante Dr. Marie‐José Casanove Dr. Nader Yaacoub Dr. Jean‐Marc Greneche Dr. Carolin Schmitz‐Antoniak Prof. Catherine Amiens 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(19):6021-6026
The effectiveness of amine–borane as reducing agent for the synthesis of iron nanoparticles has been investigated. Large (2–4 nm) Fe nanoparticles were obtained from [Fe{N(SiMe3)2}2]. Inclusion of boron in the nanoparticles is clearly evidenced by extended X‐ray absorption fine structure spectroscopy and Mössbauer spectrometry. Furthermore, the reactivity of amine–borane and amino–borane complexes in the presence of pure Fe nanoparticles has been investigated. Dihydrogen evolution was observed in both cases, which suggests the potential of Fe nanoparticles to promote the release of dihydrogen from amine–borane and amino–borane moieties. 相似文献
14.
A new route to synthesize amphiphilic core–shell particles that consist of well‐defined hydrophobic polymer cores and poly(vinylamine) (PVAm) shells has been developed. The PVAm was treated with a small amount of tert‐butyl hydroperoxide to generate free radicals that subsequently initiated both graft‐ and homo‐polymerization of vinyl monomer such as n‐butyl acrylate, methyl methacrylate, and styrene. Stable particles in the range from 100 to 250 nm in diameter with very narrow size distributions (polydispersity index between 1.08 and 1.15) were produced in high yields. TEM images of the particles revealed that they had well‐defined core–shell nanostructures with thick and hairy PVAm shells. The structures of the vinyl monomer and water‐soluble polymer were found to strongly influence the formation of particles and their sizes.
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Electrochemical Sensor for Detection of Glucose Based on Ni@Pt Core‐shell Nanoparticles Supported on Carbon 下载免费PDF全文
He Mei Wenqin Wu Beibei Yu Huimin Wu Shengfu Wang Xiuhua Zhang Qinghua Xia 《Electroanalysis》2016,28(4):671-678
In this work, Ni@Pt core‐shell nanoparticles with diameter of 3–4 nm and thin Pt shell was synthesized by a successive reduction approach using carbon as support to develop high‐performance non‐enzymatic glucose sensor. The resulting electrochemical sensor displayed good catalytic activity toward glucose oxidation, presenting a high current density of 66.9 µA mM?1 cm?2 at an applied potential of ?0.1 V. It showed a wide linear range of 0.1–30.1 mM and the limit of detection was down to 30 µM (S/N=3). Notably, it was found that the proposed sensor exhibited good selectivity to avoid the interference from ascorbic acid, uric acid, fructose and acetamidophenol. Furthermore, the feasibility of the as‐prepared non‐enzymatic glucose sensor in the determination of glucose in serum samples was successfully implemented. 相似文献
18.
Single‐Shell Carbon‐Encapsulated Iron Nanoparticles: Synthesis and High Electrocatalytic Activity for Hydrogen Evolution Reaction 下载免费PDF全文
Mohammad Tavakkoli Dr. Tanja Kallio Olivier Reynaud Prof. Albert G. Nasibulin Dr. Christoffer Johans Dr. Jani Sainio Dr. Hua Jiang Prof. Esko I. Kauppinen Prof. Kari Laasonen 《Angewandte Chemie (International ed. in English)》2015,54(15):4535-4538
Efficient hydrogen evolution reaction (HER) through effective and inexpensive electrocatalysts is a valuable approach for clean and renewable energy systems. Here, single‐shell carbon‐encapsulated iron nanoparticles (SCEINs) decorated on single‐walled carbon nanotubes (SWNTs) are introduced as a novel highly active and durable non‐noble‐metal catalyst for the HER. This catalyst exhibits catalytic properties superior to previously studied nonprecious materials and comparable to those of platinum. The SCEIN/SWNT is synthesized by a novel fast and low‐cost aerosol chemical vapor deposition method in a one‐step synthesis. In SCEINs the single carbon layer does not prevent desired access of the reactants to the vicinity of the iron nanoparticles but protects the active metallic core from oxidation. This finding opens new avenues for utilizing active transition metals such as iron in a wide range of applications. 相似文献
19.
Ran Choi Dr. Sang‐Il Choi Dr. Chang Hyuck Choi Dr. Ki Min Nam Prof. Seong Ihl Woo Prof. Joon T. Park Prof. Sang Woo Han 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(25):8190-8198
Improving the electrocatalytic activity and durability of Pt‐based catalysts with low Pt content toward the oxygen reduction reaction (ORR) is one of the main challenges in advancing the performance of polymer electrolyte membrane fuel cells (PEMFCs). Herein, a designed synthesis of well‐defined Pd@Pt core–shell nanoparticles (NPs) with a controlled Pt shell thickness of 0.4–1.2 nm by a facile wet chemical method and their electrocatalytic performances for ORR as a function of shell thickness are reported. Pd@Pt NPs with predetermined structural parameters were prepared by in situ heteroepitaxial growth of Pt on as‐synthesized 6 nm Pd NPs without any sacrificial layers and intermediate workup processes, and thus the synthetic procedure for the production of Pd@Pt NPs with well‐defined sizes and shell thicknesses is greatly simplified. The Pt shell thickness could be precisely controlled by adjusting the molar ratio of Pt to Pd. The ORR performance of the Pd@Pt NPs strongly depended on the thickness of their Pt shells. The Pd@Pt NPs with 0.94 nm Pt shells exhibited enhanced specific activity and higher durability compared to other Pd@Pt NPs and commercial Pt/C catalysts. Testing Pd@Pt NPs with 0.94 nm Pt shells in a membrane electrode assembly revealed a single‐cell performance comparable with that of the Pt/C catalyst despite their lower Pt content, that is the present NP catalysts can facilitate low‐cost and high‐efficient applications of PEMFCs. 相似文献