An ab initio Study of the C₆₀ Particle-Hole Pair C₆₀¹²⁺ and C₆₀^12-

The C60 ions C6012+ and C6012- are discussed comparatively on the basis of ab initio calculations. The basis set employed is of 3-21 G* quality. By analogy with the neutral molecule the geometry of the anion is icosahedral (Ih). Both Ih systems differ, however, in the bondlength alternation. In the neutral molecule the hexagon-hexagon bondlength exceeds the hexagon-pentagon value; vice versa in the anion. C6012+ is of Cs symmetry with a strong intermixing in the length of the two types of CC bonds. Calculated geometries, total energies and net charges are adopted to evaluate differences in the electronic structure of C6012+ and C6012-

What Controls Activity Trends of Electrocatalytic Hydrogen Evolution Reaction?-Activation Energy Versus Frequency Factor

Renewable energy storage via water electrolysis strongly depends on the design of electrified electrode–electrolyte interfaces at which electricity is converted into chemical energy. At the core of the hydrogen evolution reaction (HER) and the oxygen evolution reaction conversion efficiency are interfacial processes with complex dynamic mechanisms, whose further acceleration is practically impossible without a thorough fundamental understanding of electrocatalysis. Here, we communicate new experimental insights into HER, which will potentially further deepen our general understanding of electrocatalysis. Of special note is the very surprising observation that the most active metals (i.e., noble metals) for HER, which exhibit the lowest overpotentials at a defined current density, exhibit the highest activation energies in comparison to the other metals from the d-block. This suggests a major, if not dominant, impact of the frequency factor on activity trends and the need for deeper reconsideration of the origins of electrocatalytic activity

Influence of Precipitation Method on Acid-Base Catalyzed Reactions over Mg-Zr Mixed Oxides

To examine the promotional effect that zirconia has on magnesia in catalysis, mixed oxides were prepared by coprecipitation under controlled-pH conditions or rising-pH conditions. The resulting mixed oxides were characterized by using NH3 and CO2 adsorption microcalorimetry, X-ray diffraction, and scanning electron microscopy. The samples were also tested as catalysts for transesterification of tributyrin with methanol, coupling of acetone, and conversion of ethanol to ethene, ethanal, and butanol. Zirconia promoted the activity of MgO for both transesterification and acetone coupling reactions, presumably by exposing new acid–base pairs at the surface. During ethanol conversion, however, zirconia promoted the dehydration reactions. Characterization and reactivity results suggest that a Mg-Zr sample prepared by controlled-pH precipitation exposes more ZrO2 than a sample prepared by the rising-pH method

The potential of NO⁺ and O₂^+• in switchable reagent ion Proton Transfer Reaction time-of-flight Mass Spectrometry

Selected ion flow tube mass spectrometry (SIFT-MS) and Proton Transfer Reaction mass spectrometry with switchable reagent ion capability (PTR+SRI-MS) are analytical techniques for real-time qualification and quantification of compounds in gas samples with trace level concentrations. In the detection process, neutral compounds—mainly volatile organic compounds—are ionized via chemical ionization with ionic reagent or primary ions. The most common reagent ions are H3O+, NO+ and O2 +•. While ionization with H3O+ occurs by means of proton transfer, the ionization via NO+ and O2 +• offers a larger variety on ionization pathways, as charge transfer, hydride abstraction etc. are possible. The distribution of the reactant into various reaction channels depends not only on the usage of either NO+ or O2 +•, but also on the class of analyte compounds. Furthermore, the choice of the reaction conditions as well as the choice of either SIFT-MS or PTR+SRI-MS might have a large impact on the resulting products. Therefore, an overview of both NO+ and O2 +• as reagent ions is given, showing differences between SIFT-MS and PTR+SRI-MS as used analytical methods revealing the potential how the knowledge obtained with H3O+ for different classes of compounds can be extended with the usage of NO+ and O2 +•