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The surface chemistry of amorphous silica. Zhuravlev model

Advances in the development of novel cobalt Fischer-Tropsch catalysts for synthesis of long-chain hydrocarbons and clean fuels.

Thin films of silicon-doped Fe2O3 were deposited by APCVD (atmospheric pressure chemical vapor deposition) from Fe(CO)5 and TEOS (tetraethoxysilane) on SnO2-coated glass at 415 °C. HRSEM reveals a highly developed dendritic nanostructure of 500 nm thickness having a feature size of only 10−20 nm at the surface. Real surface area determination by dye adsorption yields a roughness factor of 21. XRD shows the films to be pure hematite with strong preferential orientation of the [110] axis vertical to the substrate, induced by silicon doping. Under illumination in 1 M NaOH, water is oxidized at the Fe2O3 electrode with higher efficiency (IPCE = 42% at 370 nm and 2.2 mA/cm2 in AM 1.5 G sunlight of 1000 W/m2 at 1.23 VRHE) than at the best reported single crystalline Fe2O3 electrodes. This unprecedented efficiency is in part attributed to the dendritic nanostructure which minimizes the distance photogenerated holes have to diffuse to reach the Fe2O3/electrolyte interface while still allowing efficient light abso...

New Benchmark for Water Photooxidation by Nanostructured α-Fe2O3 Films

Superoxide ion (O2•–) is of great significance as a radical species implicated in diverse chemical and biological systems. However, the chemistry knowledge of O2•– is rather scarce. In addition, numerous studies on O2•– were conducted within the latter half of the 20th century. Therefore, the current advancement in technology and instrumentation will certainly provide better insights into mechanisms and products of O2•– reactions and thus will result in new findings. This review emphasizes the state-of-the-art research on O2•– so as to enable researchers to venture into future research. It comprises the main characteristics of O2•– followed by generation methods. The reaction types of O2•– are reviewed, and its potential applications including the destruction of hazardous chemicals, synthesis of organic compounds, and many other applications are highlighted. The O2•– environmental chemistry is also discussed. The detection methods of O2•– are categorized and elaborated. Special attention is given to the f...

Superoxide Ion: Generation and Chemical Implications

Selectivity in propene polymerization with metallocene catalysts.

XPS and UPS study of oxygen states on silver

Hydroxides of transition metals as artificial catalysts for oxidation of water to dioxygen

A cluster model for Zn/ZSM-5 zeolite is proposed, which consists of an oxygen-bridged [Zn–O–Zn]2+ moiety attached to two framework aluminum ions of two adjacent ZSM-5 5-rings. Its stability and catalytic activity in ethane dehydrogenation were considered using the DFT method and compared with those for single Zn2+ ions in the same rings. It is shown that the oxygen-bridged Zn2+ pair is rather reactive towards ethane dissociation and that the rate-limiting step is release of hydrogen.

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DFT study of oxygen-bridged Zn2+ ion pairs in Zn/ZSM-5 zeolites

Publisher Summary This chapter focuses on the quantum-chemical cluster models of acid-base sites of oxide catalysts It is desirable, on the one hand, that the size of such a cluster should be as small as possible to permit a sufficiently rigorous quantum-chemical description of its electron properties and the interaction with adsorbed molecules On the other hand, the cluster should be large enough to produce both the real geometry of the whole crystal lattice of a catalyst and its electron structure, which are important for chemisorption The numerous quantum-chemical computations carried out for such clusters have demonstrated that chemisorptions interactions are indeed sufficiently localized, even in the case of metals where maximal cooperative effects should be anticipated Thus quantum chemistry quite unambiguously advocates the use of the local approach in describing the catalytic phenomena The cluster approach opens the way for a direct application of quantumchemical methods to the problems of chemisorption and catalysis Quantum chemistry has a rich experience in describing the local chemical interactions in molecular systems Its methods are continuously refined and improved, and the computational techniques have become more and more accurate and predictive

Georgii M. Zhidomirov

Papers

XPS and UPS study of oxygen states on silver

Hydroxides of transition metals as artificial catalysts for oxidation of water to dioxygen

DFT study of oxygen-bridged Zn2+ ion pairs in Zn/ZSM-5 zeolites

Quantum-Chemical Cluster Models of Acid-Base Sites of Oxide Catalysts

On the unusual mechanism of Lewis acidity manifestation in HZSM-5 zeolites