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Yang Liu, Feng Li, Haidong Yang, Jing Li, Ping Ma, Yan Zhu, Jiantai Ma
There is a vital need to explore highly-efficient and stable nonprecious-metal catalysts for oxygen evolution reaction (OER) to reduce the overpotential and further improve the energy conversion efficiency. Herein, we report a unique and cost-effective lyophilized and thermal two step procedure to synthesize high-performance CoFe alloy nanoparticles embedded in N-doped carbon nanosheets interspersed with carbon nanotubes (CoFe-N-CN/CNTs) hybrid. The lyophilization step during catalysts preparation is beneficial to uniform the dispersion of carbon-like precursors and avoid the agglomeration of metal particles...
May 22, 2018: ChemSusChem
Kevin W Kimura, Kevin E Fritz, Jiyoon Kim, Jin Suntivich, Héctor D Abruña, Tobias Hanrath
We demonstrate a simple strategy to enhance the CO2 reduction reaction (CO2 RR) selectivity by applying a pulsed electrochemical potential to a polycrystalline copper electrode. By controlling the pulse duration, we show that the hydrogen evolution reaction (HER) is highly suppressed to a fraction of the original value (<5 % faradaic efficiency) and selectivity for the CO2 RR dramatically improves (>75 % CH4 and >50 % CO faradaic efficiency). We attribute the improved CO2 RR selectivity to a dynamically rearranging surface coverage of hydrogen and intermediate species during the pulsing...
May 22, 2018: ChemSusChem
Ahmad A Almasalma, Esteban Mejía
C-H bond functionalization is a well-developed concept that has been thoroughly studied and gives entry to rather complex molecules without the need of previous derivatization of the substrates, although the use of copper complexes for allylic C-H bond functionalization under oxidative conditions as an alternative to the well-established palladium-based methodologies remains largely underdeveloped. Here we show for the first time a selective cross-dehydrogenative coupling reaction between underivatized allylic substrates and terminal alkynes to produce 1,4-enynes in high yields in a single step, using an in situ synthesized copper catalyst and an oxidant...
May 22, 2018: Chemistry: a European Journal
Takahiro Hayashi, Donald Hilvert, Anthony P Green
Nature employs a limited number of genetically encoded, metal coordinating residues to create metalloenzymes with diverse structures and functions. Engineered components of the cellular translation machinery can now be exploited to genetically encode non-canonical ligands with user-defined electronic and structural properties. This ability to efficiently install 'chemically programmed' ligands into proteins can provide powerful chemical probes of metalloenzyme mechanisms and presents excellent opportunities to create metalloprotein catalysts with augmented properties and novel activities...
May 22, 2018: Chemistry: a European Journal
Haoran Li, Arpan Sasmal, Xinzhe Shi, Jean-François Soulé, Henri Doucet
Palladium-catalyzed reactions using aryl halides as one of the coupling partners represent a very popular method for generating carbon-carbon bonds. However, such couplings suffer from important limitations. As most palladium catalysts are very effective for the cleavage of C-halo bonds (Halo = Cl, Br or I), in many cases, the presence of several halide functional groups on arenes is not tolerated. Since two decades, and especially during the last few years, a new class of coupling partners, benzenesulfonyl and benzenesulfinate derivatives, has emerged as a powerful alternative to aryl halides for the Pd-catalyzed C-C bond formation, as the reactions performed with these substrates generally tolerate C-halo bonds...
May 22, 2018: Organic & Biomolecular Chemistry
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
Jing Du, Zehua Zou, Ailing Yu, Cailing Xu
Exploiting highly active oxygen evolution reaction electrocatalysts is of great importance in the cost-effective generation of clean fuels. Herein, the preparation of NiMn-layered double hydroxide with selenization is adopted to reduce the charge transfer resistance of the electrocatalytic oxygen evolution reaction and enhance electrocatalytic performance. As a result, this selenization product of NiMn-layered double hydroxide can reach a current density of 10 mA cm-2 at a low overpotential of 280 mV on glassy carbon electrode in 1...
May 22, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
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
J Martínez, M Martínez de Sarasa Buchaca, F de la Cruz-Martínez, C Alonso-Moreno, L F Sánchez-Barba, J Fernandez-Baeza, A M Rodríguez, A Rodríguez-Diéguez, J A Castro-Osma, A Otero, A Lara-Sánchez
A series of alkyl aluminium complexes based on heteroscorpionate ligands were designed as catalysts for the ring-opening polymerisation of cyclic esters and ring-opening copolymerisation of epoxides and anhydrides. Treatment of AlX3 (X = Me, Et) with ligands bpzbeH [bpzbe = 1,1-bis(3,5-dimethylpyrazol-1-yl)-3,3-dimethyl-2-butoxide], bpzteH [bpzte = 2,2-bis(3,5-dimethylpyrazol-1-yl)-1-para-tolylethoxide], and (R,R)-bpzmmH [(R,R)-bpzmm = (1R)-1-{(1R)-6,6-dimethyl-bicyclo[3.1.1]-2-hepten-2-yl}-2,2-bis(3,5-dimethylpyrazol-1-yl)ethoxide] for 2 hours at 0 °C afforded the mononuclear dialkyl aluminium complexes [AlMe2{κ2-bpzbe}] (1), [AlEt2{κ2-bpzbe}] (2), [AlMe2{κ2-(R,R)-bpzmm}] (3) and [AlEt2{κ2-(R,R)-bpzmm}] (4), and the dinuclear dialkyl complexes [AlMe2{κ2-bpzte}]2 (5) and [AlEt2{κ2-bpzte}]2 (6)...
May 22, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Christoph Rameshan, Hao Li, Kresimir Anic, Matteo Roiaz, Verena Pramhaas, Raffael Rameshan, Raoul Blume, Michael Hävecker, Jan Knudsen, Axel Knop-Gericke, Gunther Rupprechter
Due to the need of sustainable energy sources, methane dry reforming (MDR) is a useful reaction for the conversion of the greenhouse gases CH&lt;sub&gt;4&lt;/sub&gt; and CO&lt;sub&gt;2&lt;/sub&gt; to synthesis gas (CO + H&lt;sub&gt;2&lt;/sub&gt;). Syngas is the basis for a wide range of commodity chemicals and can be utilized for fuel production via Fischer-Tropsch (FT) synthesis. The current study focuses on spectroscopic investigations of the surface and reaction properties of a ZrO&lt;sub&gt;2&lt;/sub&gt;/Pt inverse model catalyst, i...
May 22, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Syed N Ahmed, Waseem Haider
There has been a considerable amount of research in the development of sustainable water treatment techniques capable of improving the quality of water. Unavailability of drinkable water is a crucial issue especially in regions where conventional drinking water treatment systems fail to eradicate aquatic pathogens, toxic metal ions and industrial waste. The research and development in this area have given rise to a new class of processes called Advanced Oxidation Processes, particularly in the form of heterogeneous photocatalysis, which converts photon energy into chemical energy...
May 22, 2018: Nanotechnology
Changqing Ye, Bo Qian, Yajun Li, Min Su, Daliang Li, Hongli Bao
This paper reports a new method for the generation of substituted 1,3-enynes, whose synthesis by other methods could be a challenge. The dehydrative decarboxylative cascade coupling reaction of propargyl alcohol with alkyl peroxides is enabled by an iron catalyst and alkylating reagents. Primary, secondary, and tertiary alkyl groups can be introduced into 1,3-enynes, affording various substituted 1,3-enynes in moderate to good yields. Mechanistic studies suggest the involvement of a radical-polar crossover pathway...
May 22, 2018: Organic Letters
Ti-Wei Chen, Zhong-Qiu Li, Kang Wang, Feng-Bin Wang, Xing-Hua Xia
A novel and efficient photochemical method has been proposed for the encapsulation of Prussian blue nanoparticles (PBNPs) inside the channels of carbon nanotubes (PB-in-CNTs) in an acidic ferrocyanide solution under UV/Vis illumination and the confinement effect of CNTs on the electrochemical properties of PBNPs is systematically explored. PB-in-CNTs shows a faster electron transfer process, an enhanced electrocatalytic activity toward the reduction of H2O2 and an increased anti-base ability compared to PBNPs loaded outside of CNTs (PB-out-CNTs)...
May 22, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Luan Nguyen, Paul Pengcheng Tao, Huimin Liu, Mohamed Al-Hada, Matteo Amati, Hikmet Sezen, Luca Gregoratti, Yu Tang, Stephen D House, Franklin Feng Tao
For nanoparticles active for chemical and energy transformations in liquid environment, chemistries of surface or near-surface regions of these catalyst nanoparticles in liquid are crucial for fundamentally understanding their catalytic performances at a molecular level. Compared to catalysis at a solid-gas interface, there is very limited information on surface of these catalyst nanoparticles under working condition or during catalysis. Photoelectron spectroscopy is a surface-sensitive technique; however, it is challenging to study the surfaces of catalyst nanoparticles dispersed in liquid due to the short inelastic mean free path of photoelectrons travelling in liquid...
May 22, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
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
Binzhou Lin, Shanshan Shi, Rongcan Lin, Yiqun Cui, Meijuan Fang, Guo Tang, YuFen Zhao
The first oxidative C(sp3)-H phosphonylation of tertiary aliphatic amines has been developed. The use of cobalt acetate as catalyst, N-hydroxyphthalimide as co-catalyst, and air as oxidant enabled the conversion of tertiary aromatic and aliphatic amines into α-aminophosphonates in moderate to excellent yields under mild conditions via a cross dehydrogenative coupling reaction.
May 22, 2018: Journal of Organic Chemistry
Wuyong Zhang, Qing Qin, Lei Dai, Ruixuan Qin, Xiaojing Zhao, Xumao Chen, Daohui Ou, Tracy T Chuong, Binghui Wu, Nanfeng Zheng
Electrochemical conversion of CO2 into fuels using electricity generated from renewable sources helps to create an artificial carbon cycle. However, the low efficiency and poor stability hinder the practical use of most conventional electrocatalysts. In this work, a 2D hierarchical Pd/SnO2 structure, ultrathin Pd nanosheets partially capped by SnO2 nanoparticles, is designed to enable multi-electron transfer for selective electroreduction of CO2 into CH3OH. Such a structure design not only enhances the adsorption of CO2 on SnO2, but also weakens the binding strength of CO on Pd due to the as-built Pd-O-Sn interfaces, which is demonstrated to be critical to improve the electrocatalytic selectivity and stability of Pd catalysts...
May 22, 2018: Angewandte Chemie
Alicia L Garcia-Costa, Lucia Lopez-Perela, Xiyan Xu, Juan A Zazo, Juan J Rodriguez, Jose A Casas
This paper addresses the removal of four aromatic hydrocarbons typically found in petrochemical wastewater: benzene (B), toluene (T), o-xylene (X), and naphthalene (N), by microwave-assisted catalytic wet peroxide oxidation (MW-CWPO) using activated carbon (AC) as catalyst. Under the studied conditions, complete pollutant elimination (B, 1.28 mM; T, 1.09 mM; X, 0.94 mM; and N, 0.78 mM) was achieved, with more than 90% TOC removal after only 15-min reaction time, working at 120 °C, pH0  = 3, AC at 1 g L-1 , and H2 O2 at the stoichiometric dose...
May 21, 2018: Environmental Science and Pollution Research International
Penglin Xu, Shaojin Hu, Hou-Dao Zhang, Xiao Zheng
Recent experiments have shown that complex (1), [Fe(OTf)2(Pytacn)] (OTf = CF3SO3-, Pytacn = 1-(2'-pyridylmethyl)-4,7-dimethyl-1,4,7-triazacyclononane), is a promising artificial photosynthetic catalyst because of its distinct capability in water oxidation. Experimentalists have also synthesized several derivatives, e.g., [Fe(OTf)2(E,HPytacn)] (E = -Cl (2), -CO2Et (3) and -NO2 (4)) and [Fe(OTf)2 (E,RPytacn)] (R = -F (5) and R = -Me (6)), and proposed that the E-substituted electron-withdrawing groups could improve the catalytic efficiency...
May 22, 2018: Physical Chemistry Chemical Physics: PCCP
Dai Fei Elmer Ker, Dan Wang, Anthony William Behn, Evelyna Tsi Hsin Wang, Xu Zhang, Benjamin Yamin Zhou, Ángel Enrique Mercado-Pagán, Sungwoo Kim, John Kleimeyer, Burhan Gharaibeh, Yaser Shanjani, Drew Nelson, Marc Safran, Emilie Cheung, Phil Campbell, Yunzhi Peter Yang
Critical considerations in engineering biomaterials for rotator cuff repair include bone-tendon-like mechanical properties to support physiological loading and biophysicochemical attributes that stabilize the repair site over the long-term. In this study, UV-crosslinkable polyurethane based on quadrol (Q), hexamethylene diisocyante (H), and methacrylic anhydride (M; QHM polymers), which are free of solvent, catalyst, and photoinitiator, is developed. Mechanical characterization studies demonstrate that QHM polymers possesses phototunable bone- and tendon-like tensile and compressive properties (12-74 MPa tensile strength, 0...
May 2018: Advanced Functional Materials
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