Search results for "Hydrogen"
showing 10 items of 4254 documents
4,4'-[Thiophene-2,5-diylbis(ethyne-2,1-diyl)]dibenzonitrile
2008
In the solid state, the title compound, C(22)H(10)N(2)S, forms centrosymmetric dimers by pairs of non-classical C-H⋯S hydrogen bonds linking approximately coplanar mol-ecules. The benzene ring involved in this inter-action makes a dihedral angle of only 7.21 (16)° with the thio-phene ring, while the other benzene ring is twisted somewhat out of the plane, with a dihedral angle of 39.58 (9)°. The hydrogen-bonded dimers stack on top of each other with an inter-planar spacing of 3.44 Å. C-H⋯N hydrogen bonds link together stacks that run in approximately perpendicular directions. Each mol-ecule thus inter-acts with 12 adjacent mol-ecules, five of them approaching closer than the sum of the van …
Proton Exchange Membrane Fuel Cells (PEMFCs): Advances and Challenges
2021
The study of the electrochemical catalyst conversion of renewable electricity and carbon oxides into chemical fuels attracts a great deal of attention by different researchers. The main role of this process is in mitigating the worldwide energy crisis through a closed technological carbon cycle, where chemical fuels, such as hydrogen, are stored and reconverted to electricity via electrochemical reaction processes in fuel cells. The scientific community focuses its efforts on the development of high-performance polymeric membranes together with nanomaterials with high catalytic activity and stability in order to reduce the platinum group metal applied as a cathode to build stacks of proton …
Direct P-functionalization of azobenzene by a cationic phosphidozirconocene complex.
2016
International audience; We report that the cationic phosphidozirconocene complex [(eta(5)-C5H5)(2)Zr(PCy2)][CH3B(C6F5)(3)] (II) reacts with azobenzene, resulting in the expedient formation of Zr complex (2) bound to a tridentate PNN ligand. This reaction proceeds by a mechanism of cooperative nucleophilic substitution of hydrogen. The intermediate sigma(H) adduct (1) has been characterized by NMR spectroscopy.
Dihydrogen Activation by Antiaromatic Pentaarylboroles
2010
Facile metal-free splitting of molecular hydrogen (H2) is crucial for the utilization of H2 without the need for toxic transition-metal-based catalysts. Frustrated Lewis pairs (FLPs) are a new class of hydrogen activators wherein interactions with both a Lewis acid and a Lewis base heterolytically disrupt the hydrogen−hydrogen bond. Here we describe the activation of hydrogen exclusively by a boron-based Lewis acid, perfluoropentaphenylborole. This antiaromatic compound reacts extremely rapidly with H2 in both solution and the solid state to yield boracyclopent-3-ene products resulting from addition of hydrogen atoms to the carbons α to boron in the starting borole. The disruption of antiar…
Designing P-Chirogenic 1,2-Diphosphinobenzenes at Both P-Centers Using P(III)-Phosphinites
2016
International audience; A new enantiodivergent synthesis of P-chirogenic 1,2-diphosphinobenzenes (DP*B) bearing the chirality on one or both phosphorus centers is reported using aryne chemistry. The principle is based on successive reactions of 1,2-dibromobenzene with sec-phosphide boranes, then DABCO to remove the borane, and finally with chlorophosphines or P(III)-chirogenic phosphinites. The efficiency of this synthesis was demonstrated by the stereoselective preparation of (S,S)-1,2-bis(o-anisylphenylphosphino)benzene. A comparison of DIPAMP and homochiral DP*B ligands in asymmetric Rh- or Pd-catalyzed reactions was reported.
Photocatalytic Generation of H2 by Photoreforming of Organics in Aqueous Suspension of Nb2o5/C3n4 Composites
2023
Bare and composite materials based on C3N4 and Nb2O5 have been used as photocatalysts for the photoreforming of aqueous solutions of oxygenated compounds. Both Nb2O5 and Nb2O5/C3N4 composites have been prepared by hydrothermal synthesis and all of them were physical-chemically characterized. In this work two different carbon nitride species i.e. graphitic (g-C3N4) or thermo-etched (TE-C3N4) were used both alone or coupled with Nb2O5. The photo-reforming activity has been measured under UV irradiation by using the semiconductors in the presence of Pt as co-catalysts and, in the case of the best material, it was, for the first time, measured and compared also under natural solar irradiation. …
Photoelectron emission experiments with ECR-driven multi-dipolar negative ion plasma source
2017
Photoelectron emission measurements have been performed using a 2.45 GHz ECR-driven multi-dipolar plasma source in a low pressure hydrogen discharge. Photoelectron currents induced by light emitted from ECR zone and H− production region are measured from Al, Cu, Mo, Ta, and stainless steel (SAE 304) surfaces as a function of microwave power and neutral hydrogen pressure. The total photoelectron current from the plasma chamber wall is estimated to reach values up to 1 A for 900 W of injected microwave power. It is concluded that the volumetric photon emission rate in wavelength range relevant for photoelectron emission is a few times higher in arc discharge. peerReviewed
Bis(hydroxyammonium) hexachloridoplatinate(IV)–18-crown-6 (1/2)
2014
In the title complex, (NH3OH)2[PtCl6]·2C12H24O6, the PtIV atom is coordinated by six chloride anions in a slightly distorted octahedral geometry. The Pt—Cl bond lengths are comparable to those reported for other hexachloridoplatinate(IV) species. The hydroxyammonium groups act as linkers between the [PtCl6]2− anion and the crown ether molecules. The anion is linked to two hydroxyammonium cations via O—H...Cl hydrogen bonds and each hydroxyammonium moiety is linked to a crown ether molecule by hydrogen bonds between ammonium H atoms and 18-crown-6 O atoms. The crown ether molecules have the classic crown shape in which all O atoms are located in the inner part of the crown ether ring and all…
Understanding selective reduction reactions with heterogeneous Pd and Pt : climbing out of the black box
2016
Degradacja wodorowa niestopowej stali jakościowej DC01
2016
Celem prowadzonych badań była ocena podatności stali DC01 na niszczenie wodorowe. Badania odporności stali DC01 na niszczące działanie wodoru zrealizowano w oparciu o próbę statycznego rozciągania (slow strain) próbek w powietrzu oraz po polaryzacji katodowej. Wodorowanie stali zrealizowano w wodnym roztworze 0,1N kwasu siarkowego(VI) z dodatkiem 2 mg/dm3 tlenku arsenu(III) jako promotora wnikania wodoru przy gęstości prądu 10 i 20 mA/cm2 w czasie od 3 do 24 godzin. Zawartość wodoru w stali przed oraz po procesie elektrolitycznego nawodorowania oznaczono przy użyciu analizatora LECO ONH836. Przedmiotem szczegółowej analizy były wyniki badań mechanicznych, natomiast ich uzupełnieniem ocena m…