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 2600 m2 g−1, mechanical strengths up to 6 MPa, electrical conductivities up to 2–4 S cm−1, and densities between 0.4 and 0.7 g cm−3. In sulfuric acid electrolyte, gravimetric capacitances up to 307 F g−1 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 10–25% 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 Å and the carbonyl oxygens serve as weak hydrogen bond acceptors, thus locally enhancing the tetrahedral water hydrogen bonding structure

Odd–Even 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 UV–vis 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