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Metallic hydrogen

Feiyang Yu, Ya Gao, Zhongling Lang, Yuanyuan Ma, Liying Yin, Jing Du, Huaqiao Tan, Yonghui Wang, Yangguang Li
Molybdenum carbides are considered as one type of privileged noble-metal-free electrocatalysts for hydrogen evolution reactions (HER) due to their d-band electron structure, which is similar to Pt. Especially, the electronic structure of such materials can be further adjusted by elemental doping to improve their electrocatalytic activity. Herein, we selected the Anderson-type polyoxometalates (POMs) (NH4)n[TMMo6O24H6]·5H2O (TM = Ni2+, Co2+, n = 4; TM = Fe3+, Cr3+, n = 3) as precursors to prepare new transition-metal-doped Mo2C materials...
March 16, 2018: Nanoscale
Vincent Clesi, Mohamed Ali Bouhifd, Nathalie Bolfan-Casanova, Geeth Manthilake, Federica Schiavi, Caroline Raepsaet, Hélène Bureau, Hicham Khodja, Denis Andrault
Hydrogen has been thought to be an important light element in Earth's core due to possible siderophile behavior during core-mantle segregation. We reproduced planetary differentiation conditions using hydrogen contents of 450 to 1500 parts per million (ppm) in the silicate phase, pressures of 5 to 20 GPa, oxygen fugacity varying within IW-3.7 and IW-0.2 (0.2 to 3.7 log units lower than iron-wüstite buffer), and Fe alloys typical of planetary cores. We report hydrogen metal-silicate partition coefficients of ~2 × 10-1 , up to two orders of magnitude lower than reported previously, and indicative of lithophile behavior...
March 2018: Science Advances
Giovanni Rillo, Miguel A Morales, David M Ceperley, Carlo Pierleoni
We performed simulations for solid molecular hydrogen at high pressures (250 GPa ≤ P ≤ 500 GPa) along two isotherms at T = 200 K (phase III) and at T = 414 K (phase IV). At T = 200 K, we considered likely candidates for phase III, the C2c and Cmca12 structures, while at T = 414 K in phase IV, we studied the Pc48 structure. We employed both Coupled Electron-Ion Monte Carlo (CEIMC) and Path Integral Molecular Dynamics (PIMD). The latter is based on Density Functional Theory (DFT) with the van der Waals approximation (vdW-DF)...
March 14, 2018: Journal of Chemical Physics
Qianli Chu, Andrew J E Duncan, Giannis S Papaefstathiou, Tamara D Hamilton, Manza B J Atkinson, S V Santhana Mariappan, Leonard R MacGillivray
Enlargement of a self-assembled metal-organic rhomboid is achieved via the organic solid state. The solid-state synthesis of an elongated organic ligand was achieved by a template directed [2+2] photodimerization in a cocrystal. Initial cocrystals obtained of resorcinol template and reactant alkene afforded a 1:2 cocrystal with the alkene in a stacked yet photostable geometry. Cocrystallization performed in the presence of excess template resulted in 6:4 cocrystal composed of novel discrete 10-component hydrogen-bonded 'super-assemblies' wherein the alkenes undergo a head-to-head [2+2] photodimerization...
March 15, 2018: Journal of the American Chemical Society
Jozef Kováčik, Sławomir Dresler, Petr Babula
Short-term (24 h) responses of Cladonia arbuscula subsp. mitis (formerly known as Cladina and this name is used to distinguish the tested species) and Cladonia furcata to nickel (Ni2+ ) excess (10 or 100 μM) were compared. Cladonia accumulated more Ni at higher Ni dose (1.717 mg total Ni/g DW), K amount was unaffected and Ca amount decreased in Cladina only. Fluorescence microscopy detection of total/general ROS and hydrogen peroxide showed Ni-stimulated increase in both species being more pronounced in Cladonia and in mycobiont partner mainly...
March 6, 2018: Plant Physiology and Biochemistry: PPB
Chao Wang, Zhi-Yi Hu, Heng Zhao, Wenbei Yu, Sijia Wu, Jing Liu, Lihua Chen, Yu Li, Bao-Lian Su
We report three types of conducting polymers (CPs), polyaniline (PANI), polypyrrole (PPY) and poly (3,4-ethylenedioxythiophene) (PEDOT) to modify the surface of the CdS nanorods to probe their photocorrosion inhibition and photocatalytic hydrogen production. Various characterizations, such as high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and density function theory (DFT) calculations have been conducted to reveal the intrinsic structure of the as-constructed CPs@CdS (@ means CPs at the surface of CdS) core-shell nanorods...
March 6, 2018: Journal of Colloid and Interface Science
Stefan Ilic, Abdulaziz Alherz, Charles B Musgrave, Ksenija D Glusac
Metal-free hydrides are of increasing research interest due to their roles in recent scientific advances in catalysis, such as hydrogen activation with frustrated Lewis pairs and electrocatalytic CO2 reduction with pyridinium and other aromatic cations. The structural design of hydrides for specific applications necessitates the correct description of their thermodynamic and kinetic prowess using reliable parameters - thermodynamic hydricity (ΔGH-) and nucleophilicity (N). This review summarizes reported experimental and calculated hydricity values for more than 200 metal-free hydride donors, including carbon-, boron-, nitrogen- and silicon-based hydrides...
March 15, 2018: Chemical Society Reviews
Jan Paulo T Zaragoza, Maxime A Siegler, David P Goldberg
High-valent metal-hydroxide species are invoked as critical intermediates in both catalytic, metal-mediated O2 activation (e.g., by Fe porphyrin in Cytochrome P450) and O2 production (e.g., by the Mn cluster in Photosystem II). However, well-characterized mononuclear MIV (OH) complexes remain a rarity. Herein we describe the synthesis of MnIV (OH)(ttppc) (3) (ttppc = tris(2,4,6-triphenylphenyl) corrole), which has been characterized by X-ray diffraction (XRD). The large steric encumbrance of the ttppc ligand allowed for isolation of 3...
March 15, 2018: Journal of the American Chemical Society
Sopheavy Siek, Dalton B Burks, Deidra L Gerlach, Guangchao Liang, Jamie M Tesh, Courtney R Thompson, Fengrui Qu, Jennifer E Shankwitz, Robert M Vasquez, Nicole Chambers, Gregory J Szulczewski, Douglas B Grotjahn, Charles Edwin Webster, Elizabeth T Papish
Hydrogenation reactions can be used to store energy in chemical bonds, and if these reactions are reversible, that energy can be released on demand. Some of the most effective transition metal catalysts for CO2 hydrogenation have featured pyridin-2-ol-based ligands (e.g., 6,6'-dihydroxybipyridine (6,6'-dhbp)) for both their proton-responsive features and for metal-ligand bifunctional catalysis. We aimed to compare bidentate pyridin-2-ol based ligands with a new scaffold featuring an N -heterocyclic carbene (NHC) bound to pyridin-2-ol...
March 27, 2017: Organometallics
Zongbi Bao, Danyan Xie, Ganggang Chang, Hui Wu, Liangying Li, Wei Zhou, Hailong Wang, Zhiguo Zhang, Huabin Xing, Qiwei Yang, Michael J Zaworotko, Qilong Ren, Banglin Chen
Research on HOFs has been developed for quite a long time; however, those with both established permanent porosities and functional properties are extremely rare due to weak hydrogen-bonding interactions among molecular organic linkers which are much more fragile and difficult to stabilize. Herein, through judiciously combining the superiority of both the moderately stable coordination bonds in MOFs and hydrogen bonds, we have realized a microporous hydrogen-bonded organometallic framework HOF-21, which not only shows permanent porosity but also exhibits highly selective separation performance of C2H2/C2H4 at room temperature...
March 14, 2018: Journal of the American Chemical Society
Nihat Ege Sahin, Clement Comminges, Anthony Le Valant, Julien Kiener, Julien Parmentier, Teko Napporn, Georgian Melinte, Ovidiu Ersen, Kouakou Kokoh
Copper supported mesoporous carbon nanocatalysts (Cu/FDU-15) were synthesized using an easy and convenient one-pot soft template method for low overvoltage CO2 electroreduction. The TEM imaging revealed the presence of large Cu nanoparticles (diameter 140 nm) with Cu2O nanoparticles (16 nm) as additional phase. From the electron tomography observations, it was found that the copper particles were placed inside and on the exterior surface of the porous FDU-15 support, providing an accessible surface for electrocatalytic reactions...
March 14, 2018: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
N A Race, W Zhang, M E Screen, B A Barden, W R McNamara
A series of Fe(iii) complexes was recently reported that are active for photocatalytic hydrogen generation when paired with fluorescein and triethylamine. Herein we report an Fe(iii) complex immobilized on TiO2 and SrTiO3 that is significantly more active than the homogeneous system, achieving up to 7800 turnovers in 31 hours.
March 14, 2018: Chemical Communications: Chem Comm
Marcus Reitti, Ramani Gurubrahamam, Melanie Walther, Erik Lindstedt, Berit Olofsson
Two transition-metal-free methods to access substituted phenols via the arylation of silanols or hydrogen peroxide with diaryliodonium salts are presented. The complementary reactivity of the two nucleophiles allows synthesis of a broad range of phenols without competing aryne formation, as illustrated by the synthesis of the anesthetic Propofol. Furthermore, silyl-protected phenols can easily be obtained, which are suitable for further transformations.
March 14, 2018: Organic Letters
Hiang Kwee Lee, Charlynn Sher Lin Koh, Yih Hong Lee, Chong Liu, In Yee Phang, Xuemei Han, Chia-Kuang Tsung, Xing Yi Ling
Electrochemical nitrogen-to-ammonia fixation is emerging as a sustainable strategy to tackle the hydrogen- and energy-intensive operations by Haber-Bosch process for ammonia production. However, current electrochemical nitrogen reduction reaction (NRR) progress is impeded by overwhelming competition from the hydrogen evolution reaction (HER) across all traditional NRR catalysts and the requirement for elevated temperature/pressure. We achieve both excellent NRR selectivity (~90%) and a significant boost to Faradic efficiency by 10 percentage points even at ambient operations by coating a superhydrophobic metal-organic framework (MOF) layer over the NRR electrocatalyst...
March 2018: Science Advances
Magali Ranchou-Peyruse, Marisol Goñi-Urriza, Marion Guignard, Marjorie Goas, Anthony Ranchou-Peyruse, Rémy Guyoneaud
The strain BerOc1T was isolated from brackish sediments contaminated with hydrocarbons and heavy metals. This strain has been used as a model strain of sulfate-reducer to study the biomethylation of mercury. The cells are vibrio-shaped, motile and not sporulated. Phylogeny and physiological traits placed this strain within the genus Pseudodesulfovibrio. Optimal growth was obtained at 30 °C, 1.5 % NaCl and pH 6.0-7.4. The estimated G+C content of the genomic DNA was 62.6 mol%. BerOc1T used lactate, pyruvate, fumarate, ethanol and hydrogen...
March 13, 2018: International Journal of Systematic and Evolutionary Microbiology
Junbo Zhang, Qi Shao, Ying Zhang, Shuxing Bai, Yonggang Feng, Xiaoqing Huang
Although direct hydrogen (H2 ) oxidation to hydrogen peroxide (H2 O2 ) is considered as a promising strategy for direct H2 O2 synthesis, the desirable conversion efficiency remains formidable challenge. Herein, highly active and selective direct H2 oxidation to H2 O2 is achieved by using hollow Pd-Sn intermetallic nanoparticles (NPs) as the catalysts. By tuning the catalytic solvents and catalyst supports, the efficiency of direct H2 oxidation to H2 O2 can be optimized well with the hollow Pd2 Sn NPs/P25 exhibiting H2 O2 selectivity up to 80...
March 13, 2018: Small
Guolong Xing, Tingting Yan, Saikat Das, Teng Ben, Shilun Qiu
Self-assembled crystalline porous organic salts (CPOSs) formed by the acid-base combination and with one-dimensional polar channels containing water molecules inside the channels have been synthesized. The water content in the channels of the porous salts plays an important role in the proton conduction performance of the materials. The porous salts described in this study feature high proton conductivity at ambient conditions and can reach as high as 2.2 x10-2 S cm-1 at 333 K and high humid conditions, which is among the best conductivity values reported yet for other porous materials e...
March 13, 2018: Angewandte Chemie
Qipeng Lu, An-Liang Wang, Yue Gong, Wei Hao, Hongfei Cheng, Junze Chen, Bing Li, Nailiang Yang, Wenxin Niu, Jie Wang, Yifu Yu, Xiao Zhang, Ye Chen, Zhanxi Fan, Xue-Jun Wu, Jinping Chen, Jun Luo, Shuzhou Li, Lin Gu, Hua Zhang
Crystal-phase engineering offers opportunities for the rational design and synthesis of noble metal nanomaterials with unusual crystal phases that normally do not exist in bulk materials. However, it remains a challenge to use these materials as seeds to construct heterometallic nanostructures with desired crystal phases and morphologies for promising applications such as catalysis. Here, we report a strategy for the synthesis of binary and ternary hybrid noble metal nanostructures. Our synthesized crystal-phase heterostructured 4H/fcc Au nanowires enable the epitaxial growth of Ru nanorods on the 4H phase and fcc-twin boundary in Au nanowires, resulting in hybrid Au-Ru nanowires...
March 12, 2018: Nature Chemistry
Ammar Bin Yousaf, Muhammad Imran, Muhammad Farooq, Peter Kasak
Hydrogenation and cross-coupling reactions are of great importance for industrial applications and noble metal based catalysts are filling the void since the last few decades. However, the high cost of noble metals and poor recycling performance provides an opportunity for chemists to look for alternate options. Herein, we present the use of Lanthanum hydroxide as support for loading ultra-low amount of Pd for hydrogenation and cross-coupling reactions. Lanthanum hydroxide having controlled morphologies comprises exposed crystallographic facets which interact with small sized Pd NPs and shows versatile and effective catalytic performance...
March 12, 2018: Scientific Reports
Gautam Achar, C R Shahini, Siddappa A Patil, Jan Grzegorz Małecki, Szu-Hua Pan, Albert Lan, Xuan-Ren Chen, Srinivasa Budagumpi
In this contribution, a series of sterically-encumbered coumarin substituted benzimidazole-based N-heterocyclic carbene (NHC) precursors (1-12) and their silver(I)-NHC complexes (13-24) are reported. Molecular structure of NHC precursors 8 and 12 and cationic complexes 15 and 16 was established by single crystal X-ray diffraction method. The silver(I) complexes demonstrated various significant intramolecular agostic-like interactions operating between the metal center and the hydrogen atoms of the substituents alongside a variety of feeble π-π stacking interactions...
February 22, 2018: Journal of Inorganic Biochemistry
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