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https://www.readbyqxmd.com/read/28640611/lattice-hydride-mechanism-in-electrocatalytic-co2%C3%A2-reduction-by-structurally-precise-copper-hydride-nanoclusters
#1
Qing Tang, Yongjin Lee, Dai-Ying Li, Woojun Choi, C W Liu, Dongil Lee, De-En Jiang
Copper electrocatalysts can reduce CO2 to hydrocarbons at high overpotentials. However, mechanistic understanding of CO2 reduction on nanostructured Cu catalysts has been lacking. Herein we show that the structurally precise ligand-protected Cu-hydride nanoclusters, such as Cu32H20L12 (L is a dithiophosphate ligand), offer unique selectivity for electrocatalytic CO2 reduction at low overpotentials. Our density functional theory (DFT) calculations predict that the presence of the negatively charged hydrides in the copper cluster plays a critical role in determining the selectivity of the reduction product, yielding HCOOH over CO with a lower overpotential...
June 22, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28636684/balanced-work-function-as-a-driver-for-facile-hydrogen-evolution-reaction-comprehension-and-experimental-assessment-of-interfacial-catalytic-descriptor
#2
Aleksandar R Zeradjanin, Ashokanand Vimalanandan, George Polymeros, Angel A Topalov, Karl J J Mayrhofer, Michael Rohwerder
A major step in the development of (electro)catalysis would be the possibility to estimate accurately the energetics of adsorption processes related to reaction intermediates. Computational chemistry (e.g. using DFT) developed significantly in that direction and allowed the fast prediction of (electro)catalytic activity trends and improved the general understanding of adsorption at electrochemical interfaces. However, building a reliable and comprehensive picture of electrocatalytic reactions undoubtedly requires experimental assessment of adsorption energies...
June 21, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28636605/catalytic-allylic-oxidation-of-internal-alkenes-to-a-multifunctional-chiral-building-block
#3
Liela Bayeh, Phong Q Le, Uttam K Tambar
The stereoselective oxidation of hydrocarbons is one of the most notable advances in synthetic chemistry over the past fifty years. Inspired by nature, enantioselective dihydroxylations, epoxidations and other oxidations of unsaturated hydrocarbons have been developed. More recently, the catalytic enantioselective allylic carbon-hydrogen oxidation of alkenes has streamlined the production of pharmaceuticals, natural products, fine chemicals and other functional materials. Allylic functionalization provides a direct path to chiral building blocks with a newly formed stereocentre from petrochemical feedstocks while preserving the olefin functionality as a handle for further chemical elaboration...
June 21, 2017: Nature
https://www.readbyqxmd.com/read/28636401/one-step-solvothermal-synthesis-of-petalous-carbon-coated-cu-doped-cds-nanocomposites-with-enhanced-photocatalytic-hydrogen-production
#4
Bin He, Ren Liu, Jiabin Ren, Caijian Tang, Yijun Zhong, Yong Hu
Metal ion doping and nanocoating to CdS photocatalyst have been proved to be effective strategies to inhibit photocorrosion and improve photocatalytic performance. In this study, carbon-coated Cu+-doped CdS nanocomposites (C-Cu-CdS) with a stable petalous structure and highly uniform size distribution were successfully synthesized via a facile one-step solvothermal method. Both Cu+ doping and carbon coating to the CdS photocatalyst are realized in this one-step strategy. Benefiting from the unique core-shell structure and metal ion doping, the as-prepared C-Cu-CdS catalyst exhibits significantly enhanced photostability and visible-light-driven photocatalytic efficiency...
June 21, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28636350/integrating-a-semi-transparent-fullerene-free-organic-solar-cell-in-tandem-with-a-bivo4-photoanode-for-unassisted-solar-water-splitting
#5
Yuelin Peng, Gokul V Govindaraju, Dong Ki Lee, Kyoung-Shin Choi, Trisha L Andrew
We report an unassisted solar water splitting system powered by a diketopyrrolopyrrole (DPP)-containing semi-transparent organic solar cell. Two major merits of this fullerene-free solar cell enable its integration with a BiVO4 photoanode. First is the high open circuit voltage and high fill factor displayed by this single junction solar cell, which yields sufficient power to effect water splitting when serially-connected to an appropriate electrode/catalyst. Second, the wavelength-resolved photoaction spectrum of the DPP-based solar cell has minimal overlap with that of the BiVO4 photoanode, thus ensuring that light collection across these two components can be optimized...
June 21, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28636035/development-of-air-stable-hydrogen-evolution-catalysts
#6
Biswajit Mondal, Abhishek Dey
Obtaining abundant pure hydrogen by reduction of water has an important implication in the development of clean and renewable energy. Hence research focused on the development of non-noble metal based facile and energy efficient catalysts for proton reduction is on the rise. However, for practical utilization, it is necessary that these complexes function unabated in the presence of atmospheric oxygen and other common contaminants in abundant water sources. There has been very little activity towards the development of oxygen-tolerant hydrogen producing catalysts...
June 21, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28635998/heterogeneous-catalytic-hydrogenation-of-co2-by-metal-oxides-defect-engineering-perfecting-imperfection
#7
Jia Jia, Chenxi Qian, Yuchan Dong, Young Feng Li, Hong Wang, Mireille Ghoussoub, Keith T Butler, Aron Walsh, Geoffrey A Ozin
Metal oxides with their myriad compositions, structures and bonding exhibit an incredibly diverse range of properties. It is however the defects in metal oxides that endow them with a variety of functions and it is the ability to chemically tailor the type, population and distribution of defects on the surface and in the bulk of metal oxides that delivers utility in different applications. In this Tutorial Review, we discuss how metal oxides with designed defects can be synthesized and engineered, to enable heterogeneous catalytic hydrogenation of gaseous carbon dioxide to chemicals and fuels...
June 21, 2017: Chemical Society Reviews
https://www.readbyqxmd.com/read/28635285/triazole-triazine-functionalized-mesoporous-silica-as-a-hybrid-material-support-for-palladium-nanocatalyst
#8
Ali Saad, Christian Vard, Manef Abderrabba, Mohamed Mehdi Chehimi
Noble and precious metal catalysts are sought for their remarkable efficiency in catalyzing numerous reactions in heterogeneous phase. However, they are costly and request the development of high surface area supports that favor their strong immobilization, dispersion and stability. Towards this end, mesoporous silica-based materials can be regarded as unique supports for nanometric-sized noble metal catalysts provided they are functionalized with appropriate ligands. In this work, mesoporous silica SBA-15 was prepared and modified with 3-azidopropyltriethoxysilane then clicked with alkyne derivatives of 1,3,5-triazines complex ligand...
June 21, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28632391/transfer-hydrogenation-of-carbonyl-derivatives-catalyzed-by-an-inexpensive-phosphine-free-manganese-precatalyst
#9
Antoine Bruneau-Voisine, Ding Wang, Vincent Dorcet, Thierry Roisnel, Christophe Darcel, Jean-Baptiste Sortais
A very simple and inexpensive catalytic system based on abundant manganese as transition metal and on an inexpensive phosphine-free bidendate ligand, 2-(aminomethyl)pyridine, has been developed for the reduction of a large variety of carbonyl derivatives with 2-propanol as hydrogen donor. Remarkably, the reaction proceeds at room temperature with low catalyst loading (down to 0.1 mol %) and exhibits a good tolerance toward functional groups. High TON (2000) and TOF (3600 h(-1)) were obtained.
June 20, 2017: Organic Letters
https://www.readbyqxmd.com/read/28632338/difluoromethylation-reactions-of-organic-compounds
#10
Damian E Yerien, Sebastian Barata-Vallejo, Al Postigo
The relevance of the -CF2H moiety has attracted considerable attention from organic synthetic and medicinal chemistry communities, because this group can act as a more lipophilic isostere of the carbinol, thiol, hydroxamic acid or amide groups. Being weakly acidic, the CF2H moiety can establish hydrogen bonding interactions to improve the binding selectivity of biologically active compounds. Therefore, the hydroxyl, amino, and thio substituents of lead structures are routinely replaced by a CF2H motif in drug discovery, with great benefits in the pharmacological activity of drugs and drug candidates and agrochemicals...
June 20, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28632318/-the-easier-the-better-preparation-of-efficient-photocatalysts-metastable-poly-heptazine-imide-salts
#11
Zupeng Chen, Aleksandr Savateev, Sergey Pronkin, Vasiliki Papaefthimiou, Christian Wolff, Marc Georg Willinger, Elena Willinger, Dieter Neher, Markus Antonietti, Dariya Dontsova
Cost-efficient, visible-light-driven hydrogen production from water is an attractive potential source of clean, sustainable fuel. Here, it is shown that thermal solid state reactions of traditional carbon nitride precursors (cyanamide, melamine) with NaCl, KCl, or CsCl are a cheap and straightforward way to prepare poly(heptazine imide) alkali metal salts, whose thermodynamic stability decreases upon the increase of the metal atom size. The chemical structure of the prepared salts is confirmed by the results of X-ray photoelectron and infrared spectroscopies, powder X-ray diffraction and electron microscopy studies, and, in the case of sodium poly(heptazine imide), additionally by atomic pair distribution function analysis and 2D powder X-ray diffraction pattern simulations...
June 20, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28631924/insight-into-the-bonding-mechanism-and-the-bonding-covalency-in-noble-gas-noble-metal-halides-an-nbo-nrt-investigation
#12
Guiqiu Zhang, Lei Fu, Hong Li, Xuchan Fan, De-Zhan Chen
The bonding between noble gas and noble metal halide like hydrogen bonding (H-bonding) motivates us to investigate the bonding mechanism and the bonding covalency in NgMX (Ng = He, Ne, Ar, Kr, Xe, Rn; M = Cu, Ag, Au; X = F, Cl, Br, I) complexes using Natural Bond Orbital (NBO) and Natural Resonance Theory (NRT) methods. In this study, we introduce the new resonance bonding model in H-bonding into NgMX bonding. We provide strong evidence for resonance bonding involving two important resonance structures: Ng: M-X ↔ Ng(+)-M :X(-) in each of NgMX complexes, originating in the nNg→σ*MX hyperconjugative interaction...
June 20, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28631922/dual-property-supramolecular-h-bonded-15-crown-5-ln-iii-chains-joint-magneto-luminescence-and-ab-initio-studies
#13
Majeda Al Hareri, Zineb Ras Ali, Jeffery Regier, Emma L Gavey, Luis D Carlos, Rute A S Ferreira, Melanie Pilkington
Two complexes comprising 9-coordinate capped square antiprismatic [Ln(NO3)3(OH2)2(MeOH)] units [Ln(III) = Dy 6; Tb 7] are reported in which the metal complexes are hydrogen-bonded to 15C5 (15-crown-5) macrocycles to form supramolecular chains, {[Ln(NO3)3(OH2)2(MeOH)]·(15C5)}n. Alternating current magnetic susceptibility measurements supported by ab initio studies show field-induced SMM (single-molecule magnet) behavior for 6, but rapid relaxation of the magnetization for 7 because of the presence of dominant quantum tunneling processes as evidenced by the presence of a significant calculated tunnel splitting within the ground-state multiplet...
June 20, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28631861/renewable-molecular-flasks-with-nadh-models-combination-of-light-driven-proton-reduction-and-biomimetic-hydrogenation-of-benzoxazinones
#14
Liang Zhao, Jianwei Wei, Junhua Lu, Cheng He, Chunying Duan
Using small molecules with defined pockets to catalyze chemical transformations resulted in attractive catalytic syntheses that echo the remarkable properties of enzymes. By modulating the active site of a nicotinamide adenine dinucleotide (NADH) model in a redox-active molecular flask, we combined biomimetic hydrogenation with in situ regeneration of the active site in a one-pot transformation using light as a clean energy source. This molecular flask facilitates the encapsulation of benzoxazinones for biomimetic hydrogenation of the substrates within the inner space of the flask using the active sites of the NADH models...
June 20, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28628246/heterogeneous-catalysis-in-zeolites-mesoporous-silica-and-metal-organic-frameworks
#15
REVIEW
Jie Liang, Zibin Liang, Ruqiang Zou, Yanli Zhao
Crystalline porous materials are important in the development of catalytic systems with high scientific and industrial impact. Zeolites, ordered mesoporous silica, and metal-organic frameworks (MOFs) are three types of porous materials that can be used as heterogeneous catalysts. This review focuses on a comparison of the catalytic activities of zeolites, mesoporous silica, and MOFs. In the first part of the review, the distinctive properties of these porous materials relevant to catalysis are discussed, and the corresponding catalytic reactions are highlighted...
June 19, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28627526/polymeric-carbon-nitride-for-solar-hydrogen-production
#16
Xiaobo Li, Anthony F Masters, Thomas Maschmeyer
If solar hydrogen production from water is to be a realistic candidate for industrial hydrogen production, the development of photocatalysts, which avoid the use of expensive and/or toxic elements is highly desirable from a scalability, cost and environmental perspective. Metal-free polymeric carbon nitride is an attractive material that can absorb visible light and produce hydrogen from water. This article reviews recent developments in polymeric carbon nitride as used in photocatalysis and then develops the discussion focusing on the three primary processes of a photocatalytic reaction: light-harvesting, carrier generation/separation/transportation and surface reactions...
June 19, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28627252/phytochemical-and-antioxidant-properties-of-some-cassia-species
#17
Firdose R Kolar, Chaya L Gogi, Mairunisabegum M Khudavand, Meera S Choudhari, Sindhu B Patil
In this study, the antioxidant activity of aqueous and ethanol extracts of four plants from the genus Cassia were evaluated by various antioxidant assays, including ferric reducing antioxidant power (FRAP), DPPH free radical scavenging, metal chelating activity, phosphomolybdenum reducing power, hydrogen peroxide radical scavenging, hydroxyl radical scavenging, deoxyribose degradation and β-carotene bleaching assay. The various antioxidant activities were compared to standard antioxidant such as ascorbic acid...
June 18, 2017: Natural Product Research
https://www.readbyqxmd.com/read/28626359/noble-metal-modified-octahedral-anatase-titania-particles-with-enhanced-activity-for-decomposition-of-chemical-and-microbiological-pollutants
#18
Z Wei, M Endo, K Wang, E Charbit, A Markowska-Szczupak, B Ohtani, E Kowalska
Octahedral anatase particles (OAPs) were prepared by hydrothermal (HT) reaction of titanate nanowires (TNWs). OAPs were modified with noble metals (Au, Ag, Cu and Pt) by two photodeposition methods: in the absence and in the initial presence of oxygen in the system. Photocatalytic activities for oxidative decomposition of acetic acid and anaerobic dehydrogenation of methanol under UV/vis irradiation and for oxidation of 2-propanol under visible light irradiation were investigated. Antibacterial activities for bacteria (Escherichia coli) and fungi (Candida albicans) were investigated in the dark and under UV irradiation and/or visible light irradiation...
June 15, 2017: Chemical Engineering Journal
https://www.readbyqxmd.com/read/28624744/optimization-of-the-synthesis-of-pd-au-nanoalloys-confined-in-mesoporous-carbonaceous-materials
#19
Alicia Martinez de Yuso, Amandine Maetz, Yassine Oumellal, Claudia Zlotea, Jean-Marc Le Meins, Camelia Matei Ghimbeu
Pd-Au nanoalloys confined in mesoporous carbonaceous materials were synthesized by a rapid one-pot microwave assisted approach. Green polymer resins based on phloroglucinol/glyoxylic acid or glyoxal were co-assembled in the presence of a template and metallic salts followed by microwave treatment between 40 and 80°C and subsequent thermal annealing, allowing simultaneous formation of mesoporous carbonaceous materials with in-situ confined Pd-Au nanoparticles. Several Pd-Au compositions were prepared (PdxAu100-x, where x=90; 80; 70 and 50) and their impact on the alloy structure and particle size/distribution evaluated...
June 10, 2017: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/28622725/self-supported-biocarbon-fiber-electrode-decorated-with-molybdenum-carbide-nanoparticles-for-highly-active-hydrogen-evolution-reaction
#20
Jian Xiao, Yan Zhang, Zheye Zhang, Qi-Ying Lv, Feng Jing, Kai Chi, Shuai Wang
To devise and facilely synthesize an efficient noble metal-free electrocatalyst for accelerating the sluggish kinetics in the hydrogen evolution reaction (HER) are still a big challenge for electrolytic water splitting. Herein, we present a simple one-step approach for constructing self-supported biocarbon fiber cloth decorated with molybdenum carbide nanoparticles (BCF/Mo2C) electrodes by a direct annealing treatment of the Mo oxyanions loaded cotton T-shirt. The Mo2C nanoparticles not only serve as the catalytic active sites toward the HER but also enhance the hydrophilicity and conductivity of resultant electrodes...
June 16, 2017: ACS Applied Materials & Interfaces
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