Catalytic combustion of toluene over electrochemically promoted Ag catalyst

Evident electrochemical promotion of the complete catalytic oxidation of toluene in the temperature range 300-330 degrees C was observed, for the first time, on a silver film catalyst prepared by direct impregnation onto a Y2O3 stabilized ZrO2 (YSZ) solid electrolyte. it was found that the toluene conversion into CO2 and H2O on such a catalyst can be significantly promoted upon cathodic polarization, i.e. oxygen removal from the catalyst surface. The promotion effect increases with the temperature within the investigated range. Furthermore, it was found that the promotion effect was also strongly influenced by toluene and oxygen concentrations. With increasing the toluene concentration, the rate enhancement decreased while the Faradaic efficiency shows a volcano type behaviour. The relationships between the rate enhancement and Faradaic efficiency with the oxygen concentration are on the contrary, i.e. there is an optimum for rate enhancement when oxygen concentration is about 2%, the Faradaic efficiency monotonically decreasing with oxygen concentration. Finally, the promotion effect also increased with the thickness of Ag film, which may be interpreted by more available active sites. (C) 2008 Elsevier B.V. All rights reserved.