: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

A compendium of phase change enthalpies published in 2010 is updated to include the period 1880–2015. Phase change enthalpies including fusion, vaporization, and sublimation enthalpies are included for organic, organometallic, and a few inorganic compounds. Part 1 of this compendium includes organic compounds from C1 to C10. Part 2 of this compendium, to be published separately, will include organic and organometallic compounds from C11 to C192. Sufficient data are presently available to permit thermodynamic cycles to be constructed as an independent means of evaluating the reliability of the data. Temperature adjustments of phase change enthalpies from the temperature of measurement to the standard reference temperature, T = 298.15 K, and a protocol for doing so are briefly discussed.

Phase Transition Enthalpy Measurements of Organic and Organometallic Compounds. Sublimation, Vaporization and Fusion Enthalpies From 1880 to 2015. Part 1. C1-C10

With exceptional physicochemical properties, carbon nanomaterials (CNMs) have been widely applied in various energy and environmental applications including energy conversion, energy storage, and environmental remediation. Recent efforts have been made to prepare modified CNMs with improved electrical and chemical properties, hence broadening their potential applications. It is highly desirable to produce high-quality CNMs at a low cost and large scale, which remains a challenging task. Ball-milled CNMs (BM-CNMs) are a novel class of engineered materials that may provide new opportunities to satisfy the need. To promote the research on BM-CNMs, this work provides a comprehensive review on recent research development in (1) synthesis of various types of BM-CNMs, (2) effects of ball milling on physicochemical properties of BM-CNMs, and (3) energy and environmental applications of BM-CNMs. Different ball-milling processes for preparing BM-CNMs and modified BM-CNMs with desired particle size, structure, and s...

Ball-Milled Carbon Nanomaterials for Energy and Environmental Applications

Polyoxometalates (POMs) represent a class of nanomaterials, which hold enormous promise for a range of energy-related applications. Their promise is owing to their “special” structure that gives POMs a truly unique ability to control redox reactions in energy conversion and storage. One such amazing capability is their large number of redox active sites that arises from the complex three-dimensional cluster of metal-oxide ions linked together by oxygen atoms. Here, a critical review on how POMs emerged from being molecular clusters for fundamental studies, to next-generation materials for energy applications is provided. We highlight how exploiting the versatility and activity of these molecules can lead to improved performance in energy devices such as supercapacitors and batteries, and in energy catalyst applications. The potential of POMs across numerous fields is systematically outlined by investigating structure–property–performance relationships and the determinant factors for energy systems. Finally, the challenges and opportunities for this class of materials with respect to addressing our pressing energy-related concerns are identified.

Polyoxometalates (POMs): from electroactive clusters to energy materials

A ternary cobalt-molybdenum-vanadium layered double hydroxide nanosheet array as an efficient bifunctional electrocatalyst for overall water splitting.

A comprehensive analysis of the thermochemical properties of levoglucosan, using static bomb combustion calorimetry, Knudsen effusion technique, and differential scanning calorimetry, is presented. The experimental results allow us to derive the enthalpy of formation, in the gaseous phase, and thereafter to do a comparison with the same parameter obtained computationally. The good agreement between the experimental and computational results gives confidence to our determinations, particularly when they are compared with others already reported in literature. After testing the computational methodology, the ionization energy, electron affinity, proton affinity, gas-phase basicity, gas-phase acidity, and bond dissociation enthalpies of levoglucosan were also obtained. The presence of intramolecular hydrogen bonds in the most stable conformation of levoglucosan was verified by applying Quantum Theory of Atoms in Molecules calculations. Furthermore, a joint differential scanning calorimetry and temperature dy...

Levoglucosan: A Calorimetric, Thermodynamic, Spectroscopic, and Computational Investigation

CoMn-LDH@carbon nanotube composites: Bifunctional electrocatalysts for oxygen reactions

The development of carbon-based metal-free electrocatalysts for the oxygen reduction reaction (ORR) is one of the most attractive topics in fuel cell field. Herein, we report the application of two sustainable sucrose-based activated carbons (ACs), denominated SC800 and SH800, as ORR electrocatalysts. In alkaline medium the ACs showed similar onset potentials at Eonset ≈ −0.20 V vs. Ag/AgCl (0.76 V vs. ERHE), which are 0.06 V more negative than that observed for 20 wt% Pt/C used as a reference. Higher diffusion-limiting current densities (jL(−1.0 V, 1600 rpm) = −3.44 mA cm−2) were obtained for the SH800 electrocatalyst, in contrast to SC800 (jL(−1.0 V, 1600 rpm) = −3.04 mA cm−2). These differences can be related with their different textural properties. The SH800 electrocatalyst revealed a higher specific surface area (ABET ≈ 2500 m2 g−1), larger micropores (widths between 0.7 and 2 nm) and sponge-like morphology. Conversely, SC800 showed a spherical shape, ABET ≈ 1400 m2 g−1 and narrow micropores with pore width <0.7 nm. Both ACs were neither selective to 2- or 4-electron ORR processes, opposing Pt/C which showed selectivity towards direct O2 reduction to water. SH800 and SC800 showed very similar Tafel plots, but with SH800 showing in both low and high current density regions, the lowest slopes values 53/171 mV dec−1 vs. 68/217 mV dec−1. Furthermore, the ACs presented excellent tolerance to methanol, with the SH800 electrocatalyst also showing greater long-term electrochemical stability than the Pt/C electrocatalyst which are very important advantages. The ACs-based electrocatalysts also showed ORR catalytic activity in acidic media, which makes them promising candidates for applications with acidic electrolytes (e.g. proton exchange fuel cells). In this case, Eonset = 0.06 V vs. Ag/AgCl (0.41 V vs. ERHE) for SC800 and Eonset = −0.01 V vs. Ag/AgCl (0.34 V vs. ERHE) for SH800, and the diffusion-limiting current densities are very similar for both ACs (jL = −2.59/−2.76 mA cm−2 at −1.3 V vs. Ag/AgCl, at 1600 rpm). SH800 and SC800 Tafel plots also showed two different slopes, but with higher values in both low and high current density regions, when compared with those obtained in an alkaline medium; still SH800 continues to show the lowest slopes.

Sucrose-derived activated carbons: electron transfer properties and application as oxygen reduction electrocatalysts

The enthalpy of hydrogenation of uracil was derived from the experimental enthalpies of formation, in the gaseous phase, of uracil and 5,6-dihydrouracil, in order to analyze its aromaticity. The enthalpy of formation of 5,6-dihydrouracil was obtained from combustion calorimetry, Knudsen effusion technique and Calvet microcalorimetry results. High-level computational methods were tested for the enthalpy of hydrogenation of uracil, but only with G3 was possible to obtain results in agreement with the experimental ones. It was found that uracil possesses 30.0% of aromatic character in the gaseous phase. Using both implicit, explicit, and hybrid solvation methods, it was possible to obtain a reference value for the enthalpy of hydrogenation of uracil in the aqueous solution and the effect of polarity and hydrogen bonds on the aromaticity of uracil was analyzed. The value of the hydrogenation enthalpy of uracil in aqueous solution was compared with the experimental value in the crystal phase, also dominated by...

Inês M. Rocha

Papers

Levoglucosan: A Calorimetric, Thermodynamic, Spectroscopic, and Computational Investigation

CoMn-LDH@carbon nanotube composites: Bifunctional electrocatalysts for oxygen reactions

Sucrose-derived activated carbons: electron transfer properties and application as oxygen reduction electrocatalysts

Is Uracil Aromatic? The Enthalpies of Hydrogenation in the Gaseous and Crystalline Phases, and in Aqueous Solution, as Tools to Obtain an Answer

N-doped Carbon Nanotubes for the Oxygen Reduction Reaction in Alkaline Medium: Synergistic Relationship between Pyridinic and Quaternary Nitrogen