DFT and in situ EXAFS investigation of gold/ceria-zirconia low-temperature water gas shift catalysts: Identification of the nature of the active form of gold

A combined experimental and theoretical investigation of the nature of the active form of gold in oxide-supported gold catalysts for the water gas shift reaction has been performed. In situ extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) experiments have shown that in the fresh catalysts the gold is in the form of highly dispersed gold ions. However, under water gas shift reaction conditions, even at temperatures as low as 100 degrees C, the evidence from EXAFS and XANES is only 14 consistent with rapid, and essentially complete, reduction of the gold to form metallic clusters containing about 50 atoms. The presence of Au-Ce distances in the EXAFS spectra, and the fact that about 15% of the gold atoms can be reoxidized after exposure to air at 150 degrees C, is indicative of a close interaction between a fraction (ca. 15%) of the gold atoms and the oxide support. Density functional theory (DFT) calculations are entirely consistent with this model and suggest that an important aspect of the active and stable form of gold under water gas shift reaction conditions is the location of a partially oxidized gold (Audelta+) species at a cerium cation vacancy in the surface of the oxide support. It is found that even with a low loading gold catalysts (0.2%) the fraction of ionic gold under water gas shift conditions is below the limit of detection by XANES (<5%). It is concluded that under water gas shift reaction conditions the active form of gold comprises small metallic gold clusters in intimate contact with the oxide support.

Choose Life not Economic Growth: Critical Social Theory for People, Planet and Flourishing in the ‘Age of Nature’

Choose a fucking big television Choose washing machines, cars, compact disc players, and electrical tin openers... Choose leisure wear and matching luggage. Choose a three piece suite on hire purchase in a range of fucking fabrics. Choose DIY and wondering who you are on a Sunday morning. Choose sitting on that couch watching mind-numbing sprit-crushing game shows Stuffing fucking junk food into your mouth. Choose your future. Choose life. (Irvine Welsh, Trainspotting, 1996) Anyone who believes exponential growth can go on forever in a finite world is either a madman or an economist (Kenneth Boulding)

In situ study of ozone and hybrid plasma Ag-Al catalysts for the oxidation of toluene: Evidence of the nature of the active sites

Silver colloids have been prepared by reducing AgNO3 in aqueous solution and embeded in alumina following a sol-gel procedure in the presence of Pluronic 84 ((EO)(19)(PO)(39)(EO)(19)), as surfactant. Plasma-catalytic experiments aimed at the mineralization of toluene showed that the selectivity to CO2 was significantly increased in the presence of Ag catalysts compared with results obtained using the plasma alone. In-situ studies of the ozone interaction with catalysts provide an insight into the nature of the active sites of supported silver colloids for mineralization reactions. It is noticeable that when ozone is chemisorbed on embedded Ag colloidal catalysts no change in the silver oxidation state or size is found. The population of the chemisorbed species is higher at lower temperatures, where the non-selective decomposition of ozone is smaller. The catalysts exhibit high stability, preserving the structural and textural properties after the catalytic tests, that is indeed very important in the presence of ozone. (C) 2011 Elsevier B.V. All rights reserved.

Sexing up the city in the international beauty contest: the performative nature of spatial planning and the fictive spectacle of place branding

This paper responds to recent calls for more academic research and critical discussion on the relationship between spatial planning and city branding. Through the lens of Liverpool, the article analyses how key planning projects have delivered major transformations in the city's built environment and cultural landscape. More specifically, in concentrating on the performative nature of spatial planning it reveals the physical, symbolic and discursive re-imaging of Liverpool into a 'world class city'. Another aspect of the paper presents important socioeconomic datasets and offers a critical reading of the re-branding in showing how it presents an inaccurate representation of Liverpool. The evidence provided indicates that a more accurate label for Liverpool is a polarised and divided city, thereby questioning the fictive spectacle of city branding. Finally, the paper ends with some critical commentary on the role of spatial planning as an accessory to the sophistry of city branding.

Promotion of Ceria Catalysts by Precious Metals: Changes in Nature of the Interaction under Reducing and Oxidizing Conditions

By depositing ceria over supported precious metal (PM) catalysts and characterizing them with in situ diffuse reflectance UV (DR UV) and in situ Raman spectroscopy, we have been able to prove a direct correlation between a decrease in ceria band gap and the work function of the metal under reducing conditions. The PM ceria interaction results in changes on the ceria side of the metal ceria interface, such that the degree of oxygen vacancy formation on the ceria surface also correlates with the precious metal work function. Nevertheless, conclusive evidence for a purely electronic interaction could not be provided by X-ray photoelectron spectroscopy (XPS) analysis. On the contrary, the results highlight the complexity of the PM ceria interaction by supporting a spillover mechanism resulting from the electronic interaction under reducing conditions. Under oxidizing conditions, another effect has been observed; namely, a structural modification of ceria induced by the presence of PM cations. In particular, we have been able to demonstrate by in situ Raman spectroscopy that, depending on the PM ionic radius, it is possible to create PM ceria solid solutions. We observed that this structural modification prevails under an oxidizing atmosphere, whereas electronic and chemical interactions take place under reducing conditions.