Subnanometer cobalt oxide clusters as selective low temperature oxidative dehydrogenation catalysts.

The discovery of more efficient, economical, and selective catalysts for oxidative dehydrogenation is of immense economic importance. However, the temperatures required for this reaction are typically high, often exceeding 400 °C. Herein, we report the discovery of subnanometer sized cobalt oxide clusters for oxidative dehydrogenation of cyclohexane that are active at lower temperatures than reported catalysts, while they can also eliminate the combustion channel.

Carbocation Stability in H-ZSM5 at High Temperature.

Zeolites are common catalysts for multiple industrial applications, including alcohol dehydration to produce olefins, and given their commercial importance, reaction mechanisms in zeolites have long been proposed and studied. Some proposed reaction mechanisms for alcohol dehydration exhibit noncyclic carbocation intermediates or transition states that resemble carbocations, and several previous studies suggest that the tert-butyl cation is the only noncyclic cation more stable than the corresponding chemisorbed species with the hydrocarbon bound to the framework oxygen (i.e.

Hydrodeoxygenation by deuterium gas--a powerful way to provide insight into the reaction mechanisms.

This study demonstrates the use of isotopic labelling and NMR to study the HDO process. As far as we know, this is the first reported effort to trace the incorporation of hydrogen in the HDO process of lignin pyrolysis oil thereby providing key fundamental insight into its reaction mechanism.

Size-dependent subnanometer Pd cluster (Pd4, Pd6, and Pd17) water oxidation electrocatalysis.

Water oxidation is a key catalytic step for electrical fuel generation. Recently, significant progress has been made in synthesizing electrocatalytic materials with reduced overpotentials and increased turnover rates, both key parameters enabling commercial use in electrolysis or solar to fuels applications. The complexity of both the catalytic materials and the water oxidation reaction makes understanding the catalytic site critical to improving the process.

Magnetism in lithium-oxygen discharge product.

Nonaqueous lithium-oxygen batteries have a much superior theoretical gravimetric energy density compared to conventional lithium-ion batteries, and thus could render long-range electric vehicles a reality. A molecular-level understanding of the reversible formation of lithium peroxide in these batteries, the properties of major/minor discharge products, and the stability of the nonaqueous electrolytes is required to achieve successful lithium-oxygen batteries. We demonstrate that the major discharge product formed in the lithium-oxygen cell, lithium peroxide, exhibits a magnetic moment.

Quaternary amine-induced peptide degradation via cyclization.

In this study, we investigated intramolecular cyclizations in peptides containing quaternary amines. Two types of cyclization reactions are studied: (a) those involving a trimethylammonium butyric acid (TMAB) charge tag and (b) those involving trimethylated lysine. Both types of reactions result in the release of trimethylamine via an S(N)2 mechanism involving a lone pair of electrons on the oxygen or nitrogen.

Collective vibrations in cluster models for semiconductor surfaces: vibrational spectra of acetylenyl and methylacetylenyl functionalized Si(111).

The geometries and harmonic vibrational frequencies of the acetylenyl and methylacetylenyl functionalized Si(111) surfaces are investigated using quantum chemical calculations. The vibrational spectra are computed using a previously introduced method whereby the collective vibrational modes that correspond to the vibrations of the infinite periodic system are derived from modest sized cluster models. Our predictions should be useful for the interpretation of the experimental spectra when they become available.

The emergence of collective vibrations in cluster models: quantum chemical study of the methyl-terminated Si(111) surface.

In this paper we present structures and harmonic vibrational frequencies for the methylated silicon (111) surface from quantum chemical calculations using both cluster models and periodic boundary conditions. The results from both calculations are in very good agreement with experimentally determined frequencies. We demonstrate that relatively small cluster models already show the emergence of collective vibrational modes and provide a general method for the assignment of vibrational frequencies for extended surfaces from cluster models.