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https://www.readbyqxmd.com/read/29792321/explanation-of-dramatic-ph-dependence-of-hydrogen-binding-on-noble-metal-electrode-greatly-weakened-water-adsorption-at-high-ph
#1
Tao Cheng, Lu Wang, Boris V Merinov, William A Goddard
Hydrogen oxidation reaction (HOR) and hydrogen evolution reac-tion (HER) are both two orders slower in alkaline electrolyte than in acidic electrolyte, but no explanation has been provided. The first step towards understanding this dramatic pH-dependent HOR/HER performance is to explain the pH-dependent hydrogen binding to the electrode, a perplexing behavior observed experimentally. In this work, we carried out Quantum Mechanics Molecular Dynam-ics (QMMD) with explicit considerations of solvent and applied voltage (U) to in situ simulate water/Pt (100) interface in the condi-tion of under-potential adsorption of hydrogen (HUPD)...
May 24, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29792320/modular-cavities-induced-fit-of-polar-and-apolar-guests-into-halogen-based-receptors
#2
Kentaro Aoki, Kazuya Otsubo, Garry S Hanan, Kunihisa Sugimoto, Hiroshi Kitagawa
Neutral triangular macrocyclic compounds, [PdX2 (4,7-phen)]3 ·(DMF)3 ·Et2 O (X = Cl, Br; 4,7-phen = 4,7-phenanthroline; DMF = N, N'-dimethylformamide; Et2 O = diethyl ether), were synthesized, and their molecular structures were characterized. Solution-state 1 H NMR results suggested the formation of metal-ligand bonds, and single-crystal X-ray crystallography revealed clear triangular structures. A detailed examination of the structures indicated the formation of two kinds of cavities in the solid state, where a triangular unit works as a halogen-based receptor for polar and apolar solvents through weak hydrogen-bonding and dipole-dipole interaction...
May 24, 2018: Inorganic Chemistry
https://www.readbyqxmd.com/read/29790551/a-porous-nickel-cyclotetraphosphate-nanosheet-as-a-new-acid-stable-electrocatalyst-for-efficient-hydrogen-evolution
#3
Xiong Liu, Bo Wen, Ruiting Guo, Jiashen Meng, Ziang Liu, Wei Yang, Chaojiang Niu, Qi Li, Liqiang Mai
The stability of non-precious metal-based electrocatalysts for the acidic hydrogen evolution reaction (HER) is of great importance. Here, we have used nickel cyclotetraphosphate (Ni2P4O12) nanosheet arrays as a HER electrocatalyst for the first time. The Ni2P4O12 arrays were obtained through a facile low-temperature phosphorylation process and possess superior HER catalytic activities and stability in acid. The Ni2P4O12 delivers a small overpotential of 131.8 mV at -10 mA cm-2 and a low Tafel slope of 47.8 mV dec-1 in 0...
May 23, 2018: Nanoscale
https://www.readbyqxmd.com/read/29790329/controllable-synthesis-of-multi-heteroatoms-co-doped-hierarchical-porous-carbon-spheres-as-an-ideal-catalysis-platform
#4
Shuliang Yang, Yanan Zhu, Changyan Cao, Li Peng, Wendy L Queen, Weiguo Song
The synthesis of porous carbon spheres with hierarchical porous structures coupled with the doping of heteroatoms is particularly important for advanced applications. In this research, a new route for efficient and controllable synthesis of hierarchical porous carbon spheres co-doped with nitrogen, phosphorus, and sulfur (denoted as NPS-HPCs) was reported. This new approach combines in situ polymerization of hexachlorocyclophosphazene and 4, 4'-sulfonyldiphenol with the self-assembly of colloidal silica nanoparticles (SiO2 NPs)...
May 23, 2018: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/29790219/metal-organic-frameworks-based-on-multicentre-bonded-mi-8-m-mn-zn-clusters-with-cubic-aromaticity
#5
Bin Zhao, Huan-Cheng Hu
A new concept for constructing metal-organic frameworks (MOFs) based on multicentre-bonded [MI]8 (M = Mn, Zn) clusters with cubic aromaticity is discussed. In principle, intermolecular/intramolecular hydrogen-bonding, π***π stacking, coordinated covalent bonding and ionic bonding usually account for the structures of MOFs, and multicentered bonds generally exist in cation, anion, neutral and zwitterionic radicals, while rarely appear in MOFs. Meanwhile, aromaticity became one of the most vexing yet fascinating key concepts in chemistry since the proposition of the structure of benzene molecule in 1865...
May 23, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29789569/value-added-transformation-of-ubiquitous-substrates-into-highly-efficient-and-flexible-electrodes-for-water-splitting
#6
Atharva Sahasrabudhe, Harsha Dixit, Rahul Majee, Sayan Bhattacharyya
Herein, we present an innovative approach for transforming commonly available cellulose paper into a flexible and catalytic current collector for overall water splitting. A solution processed soak-and-coat method of electroless plating was used to render a piece of paper conducting by conformably depositing metallic nickel nanoparticles, while still retaining the open macroporous framework. Proof-of-concept paper-electrodes are realized by modifying nickel-paper current collector with model electrocatalysts nickel-iron oxyhydroxide and nickel-molybdenum bimetallic alloy through electrodeposition route...
May 22, 2018: Nature Communications
https://www.readbyqxmd.com/read/29788720/transition-metal-oxides-as-electrocatalysts-for-the-oxygen-evolution-reaction-in-alkaline-solutions-an-application-inspired-renaissance
#7
Fang Song, Lichen Bai, Aliki Moysiadou, Seunghwa Lee, Chao Hu, Laurent Liardet, Xile Hu
Water splitting is the essential chemical reaction to enable the storage of intermittent energies such as solar and wind in the form of hydrogen fuel. The oxygen evolution reaction (OER) is often considered as the bottleneck in water split-ting. While metal oxides had been reported as OER electrocatalysts more than half a century ago, the recent interest in renewable energy storage has spurred a renaissance of the studies of transition metal oxides as Earth-abundant and non-precious OER catalysts. This perspective presents major progress in several key areas of the field such as theoreti-cal understanding, activity trend, in situ and operando characterization, active site determination, and novel materi-als...
May 22, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29787255/macrocyclic-receptor-for-precious-gold-platinum-or-palladium-coordination-complexes
#8
Wenqi Liu, Allen G Oliver, Bradley D Smith
Two macrocyclic tetralactam receptors are shown to selectively encapsulate anionic, square planar chloride and bromide coordination complexes of gold(III), platinum(II), or palladium(II). Both receptors have a preorganized structure that is complementary to its precious metal guest. The receptors do not directly ligate the guest metal center but instead provide an array of arene π-electron donors that interact with the electropositive metal, and hydrogen bond donors that interact with the outer electronegative ligands...
May 22, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29787232/self-assembled-chiral-gold-supramolecules-with-efficient-laser-absorption-for-enantiospecific-recognition-of-carnitine
#9
Yu-Ting Tseng, Hsiang-Yu Chang, Scott G Harroun, Chien-Wei Wu, Shih-Chun Wei, Zhiqin Yuan, Hung-Lung Chou, Ching-Hsiang Chen, Chih-Ching Huang, Huan-Tsung Chang
Stereospecific recognition of chiral molecules is ubiquitous in chemical and biological systems, thus leading to a strong de-mand for the development of enantiomeric drugs, enantioselective sensors, and asymmetric catalysts. In this study, we demonstrate the ratio of D-Cys and L-Cys playing an important role in determining the optical properties and the structures of self-assembled Cys-Au(I) supramolecules prepared through a simple reaction of tetrachloroaurate(III) with chiral cyste-ine (Cys). The irregularly shaped -[D-Cys-Au(I)] n - or -[L-Cys-Au(I)] n - supramolecules with a size larger than 500 nm pos-sessing strong absorption in the near-UV region and chiroptical characteristics were only obtained from the reaction of Au(III) with D-Cys or L-Cys...
May 22, 2018: Analytical Chemistry
https://www.readbyqxmd.com/read/29786733/a-facet-controlled-rh-3-pb-2-s-2-nanocage-as-an-efficient-and-robust-electrocatalyst-toward-the-hydrogen-evolution-reaction
#10
Taekyung Kim, Jongsik Park, Haneul Jin, Aram Oh, Hionsuck Baik, Sang Hoon Joo, Kwangyeol Lee
Highly active and durable electrocatalysts for the hydrogen evolution reaction (HER) may play a pivotal role in commercial success of electrolytic water splitting technology. Among various material classes, binary metal sulphides show a great promise as HER catalysts because of their tunable energy levels conducive to a high catalytic activity and high robustness under harsh operating conditions. On the other hand, facet-controlled nanoparticles with controlled surface energies have gained great recent popularity as active and selective catalysts...
May 22, 2018: Nanoscale
https://www.readbyqxmd.com/read/29786726/boron-doped-graphene-nanosheet-supported-pt-a-highly-active-and-selective-catalyst-for-low-temperature-h-2-scr
#11
Maocong Hu, Zhenhua Yao, Lili Li, Yung-Hao Tsou, Liyuan Kuang, Xiaoyang Xu, Wen Zhang, Xianqin Wang
A series of boron-doped graphene-supported Pt (Pt/BG) nanosheets were designed and synthesized using a one-step facile hydrothermal method. ICP, XPS, and TPD results confirmed that boron atoms were successfully embedded into the graphene matrix. The selective catalytic reduction of nitric oxide with hydrogen (H2-SCR) was tested over Pt/BG catalysts. The multi-roles of doped-boron were investigated by Raman, BET, CO-chemisorption, H2-TPD, XPS, and NO-TPD. Boron doping led to a higher dispersion and smaller size of Pt nanoparticles, facilitated hydrogen spillover, promoted more metallic Pt formation, and increased both H2 and NO chemisorption, which were attributed to an enhanced Pt nucleation rate over doped-boron, electron donation from boron to Pt, and extra chemisorption sites...
May 22, 2018: Nanoscale
https://www.readbyqxmd.com/read/29786440/surface-ligand-promotion-of-carbon-dioxide-reduction-through-stabilizing-chemisorbed-reactive-intermediates
#12
Zhijiang Wang, Lina Wu, Kun Sun, Ting Chen, Zhaohua Jiang, Tao Cheng, William A Goddard
We have explored functionalizing metal catalysts with surface ligands as an approach to facilitate electrochemical carbon dioxide reduction reaction (CO2 RR). To provide a molecular level understanding of the mechanism by which this enhancement occurs, we combine in situ spectroscopy analysis with an interpretation based on quantum mechanics (QM) calculations. We find that a surface ligand can play a critical role in stabilizing the chemisorbed CO2 , which facilitates CO2 activation and leads to a 0.3 V decrease in the overpotential for carbon monoxide (CO) formation...
May 23, 2018: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/29783714/synthesis-of-alkanethiolate-capped-metal-nanoparticles-using-alkyl-thiosulfate-ligand-precursors-a-method-to-generate-promising-reagents-for-selective-catalysis
#13
REVIEW
Khin Aye San, Young-Seok Shon
Evaluation of metal nanoparticle catalysts functionalized with well-defined thiolate ligands can be potentially important because such systems can provide a spatial control in the reactivity and selectivity of catalysts. A synthetic method utilizing Bunte salts (sodium S -alkylthiosulfates) allows the formation of metal nanoparticles (Au, Ag, Pd, Pt, and Ir) capped with alkanethiolate ligands. The catalysis studies on Pd nanoparticles show a strong correlation between the surface ligand structure/composition and the catalytic activity and selectivity for the hydrogenation/isomerization of alkenes, dienes, trienes, and allylic alcohols...
May 18, 2018: Nanomaterials
https://www.readbyqxmd.com/read/29783143/metallic-nanocatalysts-for-electrochemical-co-2-reduction-in-aqueous-solutions
#14
Yuanxing Wang, Cailing Niu, Dunwei Wang
How to effectively and efficiently reduce carbon dioxide (CO2 ) to value-added chemicals represent a frontier in catalysis research. Due to the high activation energy needs and the endothermic nature of CO2 reduction, the reactions are difficult to carry out. When H2 O is present, hydrogen evolution reactions (HER) often compete favorably with CO2 reduction reactions. For these reactions, catalysts are of critical importance to CO2 reduction. In this article, we review the various metal nanocatalysts for electrochemical CO2 reduction (ECR) reactions...
May 16, 2018: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/29782677/ultrathin-transition-metal-dichalcogenide-3d-metal-hydroxide-hybridized-nanosheets-to-enhance-hydrogen-evolution-activity
#15
Zhengju Zhu, Huajie Yin, Chun-Ting He, Mohammad Al-Mamun, Porun Liu, Lixue Jiang, Yong Zhao, Yun Wang, Hua-Gui Yang, Zhiyong Tang, Dan Wang, Xiao-Ming Chen, Huijun Zhao
The vast majority of the reported hydrogen evolution reaction (HER) electrocatalysts perform poorly under alkaline conditions due to the sluggish water dissociation kinetics. Herein, a hybridization catalyst construction concept is presented to dramatically enhance the alkaline HER activities of catalysts based on 2D transition metal dichalcogenides (TMDs) (MoS2 and WS2 ). A series of ultrathin 2D-hybrids are synthesized via facile controllable growth of 3d metal (Ni, Co, Fe, Mn) hydroxides on the monolayer 2D-TMD nanosheets...
May 21, 2018: Advanced Materials
https://www.readbyqxmd.com/read/29782672/high-yield-production-of-monolayer-feps-3-quantum-sheets-via-chemical-exfoliation-for-efficient-photocatalytic-hydrogen-evolution
#16
Zhongzhou Cheng, Tofik Ahmed Shifa, Fengmei Wang, Yi Gao, Peng He, Kai Zhang, Chao Jiang, Quanlin Liu, Jun He
2D layered transition metal phosphorus trichalcogenides (MPX3 ) possess higher in-plane stiffness and lower cleavage energies than graphite. This allows them to be exfoliated down to the atomic thickness. However, a rational exfoliation route has to be sought to achieve surface-active and uniform individual layers. Herein, monolayered FePS3 quantum sheets (QSs) are systematically obtained, whose diameters range from 4-8 nm, through exfoliation of the bulk in hydrazine solution. These QSs exhibit a widened bandgap of 2...
May 21, 2018: Advanced Materials
https://www.readbyqxmd.com/read/29780471/direct-observation-of-supramolecular-binding-of-light-hydrocarbons-in-vanadium-iii-and-iv-metal-organic-framework-materials
#17
Zhenzhong Lu, Harry G W Godfrey, Ivan da Silva, Yongqiang Cheng, Mathew Savage, Pascal Manuel, Svemir Rudić, Anibal J Ramirez-Cuesta, Sihai Yang, Martin Schröder
Fine tuning of host-guest supramolecular interactions in porous systems enables direct control over the properties of functional materials. We report here a modification of hydrogen bonding and its effect on guest binding in a pair of redox-active metal-organic frameworks (MOFs). Oxidation of MFM-300(VIII ) {[VIII2(OH)2 (L)], LH4 = biphenyl-3,3',5,5'-tetracarboxylic acid} is accompanied by deprotonation of the bridging hydroxyl groups to afford isostructural MFM-300(VIV ), [VIV2O2 (L)]. The precise role of the hydroxyl groups, O -carboxylate centres and π-π interactions in the supramolecular binding of C2 hydrocarbons in these materials has been determined using neutron diffraction and inelastic neutron scattering, coupled with DFT modelling...
April 7, 2018: Chemical Science
https://www.readbyqxmd.com/read/29780433/influence-of-metal-deposition-and-activation-method-on-the-structure-and-performance-of-carbon-nanotube-supported-palladium-catalysts
#18
Wouter S Lamme, Jovana Zečević, Krijn P de Jong
The effects of the metal deposition and activation methods on metal particle size and distribution were investigated for carbon nanotube supported Pd catalysts. The Pd precursor was loaded by incipient wetness impregnation, ion adsorption, and deposition precipitation and was activated by thermal treatment under a nitrogen atmosphere or in the liquid phase by reduction by formaldehyde or sodium borohydride. Regardless of the metal precursor loading method, activation under a N2 atmosphere at 500 °C led to homogeneously distributed 4 nm Pd particles...
April 9, 2018: ChemCatChem
https://www.readbyqxmd.com/read/29779241/visible-light-driven-chemoselective-hydrogenation-of-nitroarenes-to-anilines-in-water-via-graphitic-carbon-nitride-metal-free-photocatalysis
#19
Gang Xiao, Peifeng Li, Yilin Zhao, Shengnan Xu, Haijia Su
Green and efficient procedures are highly required for the chemoselective hydrogenation of functionalized nitroarenes to industrially important anilines. Here, we show that visible-light-driven, chemoselective hydrogenation of functionalized nitroarenes bearing the sensitive groups to anilines can be achieved in good to excellent yields (82-100%) in water under relatively mild conditions, catalyzed by low-cost and recyclable graphitic carbon nitride. It is also applicable in gram-scale reaction with 86% yield of aniline...
May 20, 2018: Chemistry, An Asian Journal
https://www.readbyqxmd.com/read/29777615/tools-for-work-up-and-pre-purification-of-tritium-labelled-small-molecules
#20
Dieter Muri, Martin R Edelmann
This practitioner protocol describes the use and application of different types of solid phase extractions and metal scavengers for small scale reactions, particularly in the context of purifying tritiated molecules from heavily contaminated reaction mixtures. Polymer-bound strong cation exchangers are especially suitable for separating basic compounds from neutral or acidic molecules and have been widely applied in the work-up of Iridium-based hydrogen isotope exchange reactions. Polymer-bound strong anion exchangers can help to separate acidic compounds from their neutral or basic counterparts or to easily convert a TFA or formate salt to its free base after HPLC purification...
May 19, 2018: Journal of Labelled Compounds & Radiopharmaceuticals
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