New concept ultraviolet photodetectors

Abatement of various types of VOCs by adsorption/catalytic oxidation: A review

The generalization of the Local Density Approximation (LDA) method for the systems with strong Coulomb correlations is presented which gives a correct description of the Mott insulators. The LDA+U method is based on the model hamiltonian approach and allows to take into account the non-sphericity of the Coulomb and exchange interactions. parameters. Orbital-dependent LDA+U potential gives correct orbital polarization and corresponding Jahn-Teller distortion. To calculate the spectra of the strongly correlated systems the impurity Anderson model should be solved with a many-electron trial wave function. All parameters of the many-electron hamiltonian are taken from LDA+U calculations. The method was applied to NiO and has shown good agreement with experimental photoemission spectra and with the oxygen Kα X-ray emission spectrum.

http://absimage.aps.org/image/MAR06/MWS_MAR06-2005-007233.pdf

First-principles calculations of electronic structure and spectra of strongly correlated systems: the LDA+U method

A review on mercury in coal combustion process: Content and occurrence forms in coal, transformation, sampling methods, emission and control technologies

Transition metal oxides show a great variety of quantum electronic behaviours where correlations often have an important role. The achievement of high-quality epitaxial interfaces involving such materials gives a unique opportunity to engineer artificial structures where new electronic orders take place. One of the most striking result in this area is the recent observation of a two-dimensional electron gas at the interface between a strongly correlated Mott insulator LaTiO(3) and a band insulator SrTiO(3). The mechanism responsible for such a behaviour is still under debate. In particular, the influence of the nature of the insulator has to be clarified. In this article, we show that despite the expected electronic correlations, LaTiO(3)/SrTiO(3) heterostructures undergo a superconducting transition at a critical temperature T(c)(onset)~300 mK. We have found that the superconducting electron gas is confined over a typical thickness of 12 nm and is located mostly on the SrTiO(3) substrate.

/pdf/two-dimensional-superconductivity-at-a-mott-insulator-band-152kavoym8.pdf

Two-dimensional superconductivity at a Mott insulator/band insulator interface LaTiO3/SrTiO3.

Ammonia (NH3) has potentially harmful effects on human health and has recently been found to be an important factor in the formation of haze; thus, its emission control is urgent, especially during haze pollution periods. In this work, two kinds of Ag/Al2O3 catalysts with different Al2O3 particle sizes (micro-Al2O3 and nano-Al2O3) were prepared and tested for the selective catalytic oxidation of ammonia (NH3-SCO). It was shown that Ag/nano-Al2O3 was much more active than Ag/micro-Al2O3 for NH3-SCO in the low-temperature range. The results of characterization by BET, TEM, NH3-TPD, XRD, H2-TPR, UV–vis, and XAFS revealed that Ag/nano-Al2O3 possesses much smaller Ag particles and more metallic Ag species (AgNPs) and also contains abundant acid sites, which facilitate the adsorption and dissociation of NH3, therefore resulting in much higher NH3-SCO activity. In addition, on the basis of in situ DRIFTS, kinetic measurements, and DFT calculation results, we discovered that the NH3-SCO reaction over Ag/nano-Al2O...

Nanosize Effect of Al2O3 in Ag/Al2O3 Catalyst for the Selective Catalytic Oxidation of Ammonia

High-performance of Cu-TiO2 for photocatalytic oxidation of formaldehyde under visible light and the mechanism study

The Ag/Al2O3 catalyst possesses high activity for selective catalytic oxidation of ammonia (NH3–SCO), and its activity could be significantly improved by H2 pretreatment. It is generally accepted that the enhancement of Ag/Al2O3 activity after H2 reduction is due to the promoted O2 activation by metallic Ag species. Here, we show that the recovery of Bronsted acid sites via H2 reduction is also an important factor. Ag/Al2O3 and H2-pretreated Ag/Al2O3 (Ag/Al2O3–H2) catalysts were prepared and tested for the NH3–SCO performances, and also carefully characterized. It is revealed that Ag species were anchored on the Al2O3 surface through exchange between Ag+ and H+ in AlOH groups during the preparation process, and therefore occupied the Bronsted acid sites of Al2O3. H2 reduction could break the Ag–O bonds and thus recover the Bronsted acid sites. In situ DRIFTS results show that NH4+ species adsorbed on Bronsted acid sites is much more active for reaction with O2 than NH3 species adsorbed on Lewis acid sites...

Insights into the Activation Effect of H2 Pretreatment on Ag/Al2O3 Catalyst for the Selective Oxidation of Ammonia

Photocatalytic oxidation of gaseous ammonia (NH3) at room temperature is an efficient method for the elimination of NH3 emitted from indoor and outdoor sources, such as decorative materials, intensive livestock farming, chemical processes, etc. Herein, we prepared the anatase TiO2 with clean dominant {001}, {101} and {010} facets, and tested their photocatalytic activity for NH3 oxidation. The test results show that the photocatalytic activity order for NH3 oxidation is revealed as {001} > {101} > {010}. The catalysts were characterized by XRD, FE-SEM, XPS, UV–vis, in situ DRIFTS and TPD methods. It is indicated that TiO2 with dominant {001} facets has the highest separation efficiency of the photogenerated charges among three catalysts. Since the photogenerated holes is responsible for initiating the first step of NH3 oxidation, the TiO2 with dominant {001} facets demonstrated the exceptional activity. In addition, the photocatalytic oxidation of NH3 possibly follow the photo-iSCR mechanism. The photogenerated electrons activate O2 and then participate in the formation of reactive intermediate NOx followed by the photo-NH3-iSCR to final products. The present study will improve our understanding about the performance of anatase TiO2 for photocatalytic oxidation of NH3.

Facet-dependent performance of anatase TiO2 for photocatalytic oxidation of gaseous ammonia

Ag-based catalysts are efficient materials for formaldehyde (HCHO) oxidation in the low-temperature range. It has been reported that K addition can increase the catalytic performance of Ag-based catalysts, whereas the specific role of K doping remains ambiguous. In this work, Ag/Al2O3 and K–Ag/Al2O3 catalysts with different K doping levels were prepared and subsequently tested for catalytic HCHO oxidation. It was observed that K doping has a dramatic promotion effect on the activity of the Ag/Al2O3 catalyst. The 2K–Ag/Al2O3 sample was the most active catalyst, over which HCHO could be completely converted into CO2 and H2O in a gas hourly space velocity of 100 000 mL/(gcat h) at 65 °C. The catalysts were next characterized by X-ray powder diffraction, Brunauer–Emmett–Teller, transmission electron microscopy, H2-temperature-programmed reduction, UV–vis, X-ray absorption fine structure, and in situ diffuse reflectance infrared Fourier transform spectroscopy methods. The characterization results show that add...

Fei Wang

Papers

Nanosize Effect of Al2O3 in Ag/Al2O3 Catalyst for the Selective Catalytic Oxidation of Ammonia

High-performance of Cu-TiO2 for photocatalytic oxidation of formaldehyde under visible light and the mechanism study

Insights into the Activation Effect of H2 Pretreatment on Ag/Al2O3 Catalyst for the Selective Oxidation of Ammonia

Facet-dependent performance of anatase TiO2 for photocatalytic oxidation of gaseous ammonia

Specific Role of Potassium in Promoting Ag/Al2O3 for Catalytic Oxidation of Formaldehyde at Low Temperature