Félix G. Requejo

Electron Spectroscopy of Aqueous Solution Interfaces Reveals Surface Enhancement of Halides

It has been suggested that enhanced anion concentrations at the liquid/vapor interface of airborne saline droplets are important to aerosol reactions in the atmosphere. We report ionic concentrations in the surface of such solutions. Using x-ray photoelectron spectroscopy operating at near ambient pressure, we have measured the composition of the liquid/vapor interface for deliquesced samples of potassium bromide and potassium iodide. In both cases, the surface composition of the saturated solution is enhanced in the halide anion compared with the bulk of the solution. The enhancement of anion concentration is more dramatic for the larger, more polarizable iodide anion. By varying photoelectron kinetic energies, we have obtained depth profiles of the liquid/vapor interface. Our results are in good qualitative agreement with classical molecular dynamics simulations. Quantitative comparison between the experiments and the simulations indicates that the experimental results exhibit more interface enhancement than predicted theoretically.

Catalytic combustion of diesel soot particles. Activity and characterization of Co/MgO and Co,K/MgO catalysts

Abstract The catalytic combustion of diesel soot particles was studied on Co/MgO (12 wt% Co) and potassium-promoted Co/MgO (1.5 wt% K) that were calcined at different temperatures in the 300 to 700°C range. Catalyst samples were characterized by various techniques including nitrogen adsorption (BET), temperature programmed reduction (TPR),X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), electron spin resonance (ESR),X-ray photoelectron spectroscopy (XPS) and temperature programmed oxidation (TPO). As observed by TPO experiments, the catalyst activity depends strongly on the calcination temperature: calcination at 300 and 400°C produced samples that were much more active than those calcined at higher temperatures, on which an inactive Mg Co mixed oxide is formed, as suggested by TPR, ESR and XRD results. FTIR shows carbonate species on the surface. Unpromoted samples seem to correlate their activity with the amount of reducible Co species present. Potassium not only increased the sample activity, probably due to the improvement in surface mobility, but also enhanced stability at high temperatures. Experiments with different soot to catalyst ratios showed no significant variation in combustion temperature. TheK-promoted catalyst burns off soot at a temperature lower than the one needed for calcination, thus proving to be a promising catalyst.

Cationic exchange in nanosized ZnFe{sub 2}O{sub 4} spinel revealed by experimental and simulated near-edge absorption structure

The nonequilibrium cation site occupancy in nanosized zinc ferrites

Aminopropyl-modified mesoporous silica SBA-15 as recovery agents of Cu(II)-sulfate solutions: Adsorption efficiency, functional stability and reusability aspects

(\ensuremath{\sim}6--13\phantom{\rule{0.3em}{0ex}}\mathrm{nm})

Study of Nucleation and Growth Mechanism of the Metallic Nanodumbbells

with different degree of inversion (

Synthesis and characterization of gold at gold(i)-thiomalate core at shell nanoparticles.

\ensuremath{\sim}0.2

Ag2 and Ag3 clusters: synthesis, characterization, and interaction with DNA.

to 0.4) was investigated using Fe and Zn

Angle-resolved x-ray absorption near edge structure study of vertically aligned single-walled carbon nanotubes

K

TiO2-Photocatalytic Reduction of Pentavalent and Trivalent Arsenic: Production of Elemental Arsenic and Arsine

-edge x-ray absorption near edge spectroscopy (XANES) and extended x-ray absorption fine structure, and magnetic measurements. The very good agreement between experimental and ab initio calculations on the Zn

EXAFS, TDPAC and TPR characterization of PtInFerrierite: The role of surface species in the SCR of NOx with CH4

K