59 research outputs found
New Carbon Monoliths for Supercapacitor Electrodes. Looking at the Double Layer
Carbon monoliths are prepared by combining two carbon phases. A major phase is activated anthracite, which provides microporosity and a large surface area. The other phase is a carbonized polymer that provides self-consistency and contributes to densifying the monolith. Different degrees of anthracite activation and different contents of the two phases are investigated. These all-carbon monoliths have surface areas up to 2600â
m2âgâ1, mechanical strengths up to 6â
MPa, electrical conductivities up to 2â4â
Sâcmâ1, and densities between 0.4 and 0.7â
gâcmâ3. In sulfuric acid electrolyte, gravimetric capacitances up to 307â
Fâgâ1 are achieved. The double-layer capacitances due to the hydronium and bisulfate ions are separately measured, the former being approximately 25% higher than the latter. The size of the two ions electro-adsorbed at the double layer is discussed. The pseudocapacitance associated with the hydronium ion is 10â25% of the total capacitance of this ion. All of the carbon monoliths show high capacitance retention with current density; the retention of the double-layer capacitance is similar for the two types of ions and higher than the retention of the pseudocapacitance associated with the hydronium ion.Financial support through the projects of reference MAT2014-57687-R, GV/FEDER (PROMETEOII/2014/010) and University of Alicante (VIGROB-136) is gratefully acknowledged. G.M.-F. thanks MINECO for a pre-doctoral fellowship
The hydration structure of dissolved carbon dioxide from X-ray absorption spectroscopy
Abstract The dissolution of carbon dioxide in water and its subsequent hydrolysis reactions comprise one of the most central processes in all of science, yet it remains incompletely understood despite enormous effort. We report the detailed characterization of dissolved CO2 gas through the combination of X-ray spectroscopy and first principles theory. The molecule acts as a hydrophobe in water with an average hydrogen bond number of 0.56. The carbon atom interacts weakly with a single water at a distance of >2.67 Ă
and the carbonyl oxygens serve as weak hydrogen bond acceptors, thus locally enhancing the tetrahedral water hydrogen bonding structure
Evaluation of molecular radial distribution function and solvent-excluded volume with the numerical integration of the union of spheres
RISM-SCF-SEDD Study on the Symmetry Breaking of Carbonate and Nitrate Anions in Aqueous Solution
Assessment of dynamic properties of water around a monovalent ion: A classical molecular dynamics simulation study
OddâEven and Hydrophobicity Effects of Diacetylene Alkyl Chains on Thermochromic Reversibility of Symmetrical and Unsymmetrical Diyndiamide Polydiacetylenes
Two series of symmetrical (<b>S<i>x</i></b>) and
unsymmetrical (<b>U<i>y</i></b>) diacetylene monomers
containing diamide groups with different methylene units are successfully
prepared. Photopolymerization of their nanovesicles dispersed in water
is carried out by irradiation at 254 nm affording blue sols of the
corresponding PDAs. The degree of thermochromic reversibility (%DR)
of the PDA sols are determined using UVâvis spectroscopy in
order to probe effects of the number of the methylene units, <b><i>x</i></b> and <b><i>y</i></b>, within
the linker and hydrophobic tail, respectively. The complete color
reversibility (%DR > 89%) is observed only when <b><i>x</i></b> is an even number while partially reversible or irreversible
thermochromism (%DR < 65%) is displayed in the case of odd <b><i>x</i></b> number. For the <b>U<i>y</i></b> series, the color recovering ability within the heating and
cooling process increases along with the <b><i>y</i></b> number; %DR = 3, 62, and 90% for <b><i>y</i></b> = 0, 4, and 16, respectively. This work is the first direct demonstration
of the roles of number of methylene units within the diacetylene monomers
on the thermochromic reversibility of their PDAs that provide additional
dimensions for rational molecular design in the development of PDA
thermal sensors
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