Study of the Mechanism of the Electrochemical Promotion of Rh/YSZ Catalysts for C₂H₄ Oxidation Via AC Impedance Spectroscopy

摘要

The electrochemical promotion of Rh/YSZ catalysts for C₂H₄ oxidation was investigated together with the mechanism of electrochemical promotion via the use of AC impedance spectroscopy. The impedance response consists of two distinct semicircles and provides strong support for the sacrificial promoter mechanism of electrochemical promotion. The impedance analysis of the low frequency part of all spectra show the existence of a finite length Gerischer impedance which corresponds to the effective double layer formed by the spillover of promoting anionic oxygen from the YSZ support to the rhodium/gas interface and its slow consumption there by adsorbed hydrocarbon fragments. AC impedance analysis provides values both for the rate of consumption of the promoting spillover oxygen species as well as for the stability and capacitance the catalyst/gas double layer in various gaseous environments and temperatures.