Inhibition of water-gas shift reaction activity of oxide-supported Pt catalyst by H2 and CO2

A catalyst composed of platinum-group metals supported on an oxide exhibits high activity in a low-temperature water-gas shift (LT-WGS) reaction; however, the reaction rate is greatly reduced when H 2 or CO 2 , the product gases of the WGS reaction, are included in the reactant stream. In this study, we attempted to understand the origin of this activity inhibition by analyzing the kinetic data with in-situ CO-diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The WGS reaction rate decreases more severely by H 2 than CO 2 . The CO-DRIFTS spectra indicate that this can be explained by H 2 preoccupying the active sites for the WGS reaction. In addition, by comparing the kinetic data with the literature, it could be inferred that a similar inhibition mechanism is operating in other oxide-supported Pt catalysts. Considering this inhibition mechanism will be important for the development of catalysts with high WGS activity in reformate gas. • The low-temperature water-gas shift reaction activity of the Pt/CeO 2 catalyst is studied. • The inhibitory effect by H 2 and CO 2 on the reaction was investigated. • Kinetic data show that the inhibitory effect by H 2 and CO 2 is reversible. • The inhibition is more severe with H 2 than with CO 2 . • H 2 plays an inhibitory effect on the CO adsorption on Pt.