In-situ X-ray studies of clean catalytic technologies

The rational design of new heterogeneous catalysts for clean chemical technologies can be accelerated by molecular level insight into surface chemical processes. In-situ methodologies, able to provide time-resolved and/or pressure dependent information on the evolution of reacting adsorbed layers over catalytically relevant surfaces, are therefore of especial interest. Here we discuss the application of in-situ XPS and in-situ, synchronous DRIFTS/MS/XAS methodologies to elucidate the active site in Pd-catalyzed, selective aerobic oxidation of allylic alcohols.

Hydroxyapatite supported antibacterial Ag3PO4 nanoparticles

High surface area hydroxyapatites have been explored as biocompatible supports for antibacterial applications. Porosimetry, XRD, XPS and XAS reveal that Ag-doped mesoporous hydroxyapatite promotes the genesis of potent Ag3PO4 nanoparticles, effective against Staphylococcus aureus and Pseudomonas aeruginosa. © 2010 The Royal Society of Chemistry.

XPS and XMCD study of Fe3O4/GaAs interface

Ultrathin Fe oxide films of various thicknesses prepared by post-growth oxidation on GaAs(100) surface have been investigated with X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and X-ray magnetic circular dichroism (XMCD). The XPS confirms that the surfaces of the oxide are Fe3O4 rather than Fe2O3. XAS and XMCD measurements indicate the presence of insulating Fe divalent oxide phases (FeO) beneath the surface Fe3O4 layer with the sample thickness above 4 nm. This FeO might act as a barrier for the spin injection into the GaAs.

Acetic acid ketonization over Fe3O4/SiO2 for pyrolysis bio-oil upgrading

A family of silica supported, magnetite nanoparticle catalysts was synthesized and investigated for continuous flow acetic acid ketonization as a model pyrolysis bio-oil upgrading reaction. Physicochemical properties of Fe3O4/SiO2 catalysts were characterized by HRTEM, XAS, XPS, DRIFTS, TGA and porosimetry. Acid site densities were inversely proportional to Fe3O4 particle size, although acid strength and Lewis character were size invariant, and correlated with the specific activity for vapor phase acetic ketonization to acetone. A constant activation energy (~110 kJ.mol-1), turnover frequency (~13 h-1) and selectivity to acetone of 60 % were observed for ketonization across the catalyst series, implicating Fe3O4 as the principal active component of Red Mud waste.