Electron impact ionization of hydrogen-like molybdenum ions

The electron impact ionization cross sections of hydrogen-like molybdenum ions were measured with an electron beam ion trap at the electron energies of 49.4, 64.4 and 79.6 keV The results are 2.82(22) x 10(-23), 3.13(29) x 10(-23) and 3.23(51) x 10(-23) cm(2), respectively. These results are compared with the experimental results measured previously. The agreement with the results obtained with, scaling formulae is also discussed.

Catalytic Role of Metal Oxides in Gold-Based Catalysts: A First Principles Study of CO Oxidation on TiO2 Supported Au

CO oxidation on TiO2 supported Au has been studied using density functional theory calculations. Important catalytic roles of the oxide have been identified: (i) CO oxidation occurs at the interface between Au and the oxide with a very small barrier; and (ii) O-2 adsorption at the interface is the key step in the reaction. The physical origin of the oxide promotion effect has been further investigated: The oxide enhances electron transfer from the Au to the antibonding states of O-2, giving rise to (i) strong ionic bonding between the adsorbed O-2, Au, and the Ti cation; and (ii) a significant activation of O-2 towards CO oxidation.

C-H bond activation over metal oxides: A new insight into the dissociation kinetics from density functional theory

The C-H activation on metal oxides is a fundamental process in chemistry. In this paper, we report a density functional theory study on the process of the C-H activation of CH4 on Pd(111), Pt(111), Ru(0001), Tc(0001), Cu(111), PdO(001), PdO(110), and PdO(100). A linear relationship between the C-H activation barrier and the chemisorption in the dissociation final state on the metal surfaces is obtained, which is consistent with the work in the literature. However, the relationship is poor on the metal oxide surfaces. Instead, a strong linear correlation between the barrier and the lattice O-H bond strength is found on the oxides. The new linear relationship is analyzed and the physical origin is identified. (c) 2008 American Institute of Physics.

General insight into CO oxidation: A density functional theory study of the reaction mechanism on platinum oxides

CO oxidation on PtO2(110) has been studied using density functional theory calculations. Four possible reaction mechanisms were investigated and the most feasible one is the following: (i) the O at the bridge site of PtO2(110) reacts with CO on the coordinatively unsaturated site (CUS) with a negligible barrier; (ii) O-2 adsorbs on the bridge site and then interacts with CO on the CUS to form an OO-CO complex; (iii) the bond of O-OCO breaks to produce CO2 with a small barrier (0.01 eV). The CO oxidation mechanisms on metals and metal oxides are rationalized by a simple model: The O-surface bonding determines the reactivity on surfaces; it also determines whether the atomic or molecular mechanism is preferred. The reactivity on metal oxides is further found to be related to the 3rd ionization energy of the metal atom.

Microcolumn studies of dye adsorption onto manganese oxides modified diatomite

The method described here cannot fully replace the analysis of large columns by small test columns (microcolumns). The procedure, however, is suitable for speeding up the determination of adsorption parameters of dye onto the adsorbent and for speeding up the initial screening of a large adsorbent collection that can be tedious if a several adsorbents and adsorption conditions must be tested. The performance of methylene blue (MB), a basic dye, Cibacron reactive black (RB) and Cibacron reactive yellow (RY) was predicted in this way and the influence of initial dye concentration and other adsorption conditions on the adsorption behaviour were demonstrated.