Tuning the activity of Pt(111) for oxygen electroreduction by subsurface alloying

To enable the development of low temperature fuel cells, significant improvements are required to the efficiency of the Pt electrocatalysts at the cathode, where oxygen reduction takes place. Herein, we study the effect of subsurface solute metals on the reactivity of Pt, using a Cu/Pt(111) near-surface alloy. Our investigations incorporate electrochemical measurements, ultrahigh vacuum experiments, and density functional theory. Changes to the OH binding energy, ΔE(OH), were monitored in situ and adjusted continuously through the subsurface Cu coverage. The incorporation of submonolayer quantities of Cu into Pt(111) resulted in an 8-fold improvement in oxygen reduction activity. The most optimal catalyst for oxygen reduction has an ΔE(OH) ≈ 0.1 eV weaker than that of pure Pt, validating earlier theoretical predictions.     

Selective oxidation of propylene to acrolein by silica-supported bismuth molybdate catalysts

Silica-supported bismuth molybdate catalysts have been prepared by impregnation, structurally characterized and examined as improved catalysts for the selective oxidation of propylene to acrolein. Catalysts with a wide range of loadings (from 10 to 90 wt%) of beta bismuth molybdate (??-Bi₂Mo₂O₉) were studied to provide a better understanding about the distribution of active sites, and to elucidate the role of lattice oxygen in the reaction. The catalyst containing 50 wt% of beta bismuth molybdate on SiO₂ was found to possess good distribution of active sites and sufficiently high lattice oxygen, which resulted in an extraordinary increase of the catalytic activity.     

Short strong hydrogen bonds in 2-acetyl-1,8-dihydroxy-3,6-dimethylnaphthalene: an outlier to current hydrogen bonding theory?

The environmental influence on the electronic character of two O-H...O hydrogen bonds in a beta-diketone, 2-acetyl-1,8-dihydroxy-3,6-dimethylnaphthalene, is studied by low-temperature synchrotron X-ray diffraction and high-level density functional theory (DFT) calculations. It is revealed that one of the hydrogen bonds is very strong, yet partial localization is found. This result is analyzed by atoms in molecules (AIM) theory and applying the source function. Model compounds, with less steric strain, reveal that the strong hydrogen bond is not merely a result of steric compression.     

Partial agonists and subunit selectivity at NMDA receptors

Subunit-selective ligands for glutamate receptors remains an area of interest as glutamate is the major excitatory neurotransmitter in the brain and involved in a number of diseased states in the central nervous system (CNS). Few subtype-selective ligands are known, especially among the N-methyl-D-aspartic acid (NMDA) receptor class. Development of these ligands seems to be a difficult task because of the conserved region in the binding site of the NMDA receptor subunits. A few scaffolds have been developed showing potential to differentiate between the NMDA receptors.     

Reversible physical absorption of SO2 by ionic liquids

Ionic liquids can reversibly absorb large amounts of molecular SO(2) gas under ambient conditions with the gas captured in a restricted configuration, possibly allowing SO(2) to probe the internal cavity structures in ionic liquids besides being useful for SO(2) removal in pollution control.     

Buckling driven debonding in sandwich columns

A compression loaded sandwich column that contains a debond is analyzed using a geometrically non-linear finite element model. The model includes a cohesive zone along one face sheet/core interface whereby the debond can extend by interface crack growth. Two geometrical imperfections are introduced; a global imperfection of the sandwich column axis and a local imperfection of the debonded face sheet axis. The model predicts the sandwich column to be very sensitive to the initial debond length and the local face sheet imperfection. The study shows that the sensitivity to the face sheet imperfection results from two mechanisms: (a) interaction of local debond buckling and global buckling and (b) the development of a damaged zone at the debond crack tip. Based on the pronounced imperfection sensitivity, the author predicts that an experimental measurement of the strength of sandwich structures may exhibit a large scatter caused by geometrical variations between test specimens.