The study of oxygen spillover and back spillover on Pt/TiO2 by a potential dynamic sweep method

Oxygen spillover and back spillover on Pt/TiO2 catalysts have been studied by a potential dynamic sweep method. The characteristics of I-V profiles of Pt/TiO2 electrodes in the three potential sweep regions are different from those of Pt and TiO2 electrodes. The catalytic role of Pt/TiO2 in oxygen spillover and back spillover is identified. It decreases, and the electrochemical oxygen adsorption (or desorption) increases with elevating temperature of hydrogen post-treatment of Pt/TiO2; to a certain extent (hydrogen post-treatment of Pt/TiO2 at 700 degrees C), the control step of oxygen electrode process (anodic oxidation or cathodic reduction) changes from oxygen diffusion to electrochemical oxygen adsorption or desorption, respectively. Increasing the amount of Pt supported on TiO2 enhances the processes of oxygen spillover and back spillover. (C) 1999 Elsevier Science B.V. All rights reserved.

On the correlation between microstructural changes of Ag-H-ZSM-5 catalysts and their catalytic performances in the selective catalytic reduction of NOx by methane

The silver catalyzed, selective catalytic reduction (SCR) of nitrogen oxides (NOx) by CH4, is shown to be a structure-sensitive reaction. Pretreatment has a great affect on the catalytic performances. Upon thermal treatment in inert gas stream, thermal induced changes in silver morphology lead to the formation of reduced silver species of clusters and particles. Catalysis over this catalyst indicates an initially higher activity but lower selectivity for the CH4-SCR of NOx Reaction induced restructuring of silver results in the formation of ill-defined silver oxides. This, in turn, impacts the adsorption properties and diffusivity of oxygen over silver catalyst, results in the decrease in activity but increase in selectivity of Ag-H-ZSM-5 catalyst for the CH4-SCR of NO.. (c) 2004 Elsevier B.V. All rights reserved.