TAP reactor studies of the oxidizing capability of CO_2 on a Au/CeO_2 catalyst-A first step toward identifying a redox mechanism in the Reverse Water-Gas Shift reaction

摘要

As a first step toward elucidating the mechanism of the Reverse Water-Gas Shift (RWGS) reaction on a supported Au/CeO_2 catalyst, in particular the role of the redox mechanism, we have investigated the ability and activity of CO_2 for re-oxidizing a pre-reduced Au/CeO_2 catalyst surface by quantitative temporal analysis of products (TAP) measurements. It is demonstrated that a surface-reduced Au/CeO_2 catalyst can be (partially) re-oxidized by exposure to CO_2 pulses and that the surface oxygen deposited this way can be reactively removed again. The probability for oxygen deposition from CO_2, however, is significantly lower than that from O_2. Both the low reaction probability and the temperature dependence of oxygen deposition from CO_2 point to an activated step. Implications of these results for the mechanism of the RWGS reaction are discussed.