Infrared Studies of the Promoting Role of Water on the Reactivity of Pt/FeOx Catalyst in Low-Temperature Oxidation of Carbon Monoxide

Abstract

For the purpose of revealing the promoting role of water on the reactivity of the supported Pt/FeOx catalyst in the low-temperature oxidation of CO, in situ diffuse reflectance infrared Fourier transform (DRIFT) spectra were conducted to study the adsorption properties of CO under various conditions. In the case of without water (CO + O2), CO could be preferentially adsorbed on the active Pt sites, and then strongly adsorbed on the Fe3+ sites, which might considerably inhibit the ability for O2 activation, and result in the decrease of reactivity of Pt/FeOx for low-temperature oxidation of CO. For the CO oxidation under wet condition (CO + O2 + H2O), coadsorption of water and oxygen was observed, which could form surface oxygen/hydroxyls species, and significantly inhibit the adsorption of CO on the Fe3+ sites, thus avoiding the deep reduction of the active Fe3+ sites located at the boundaries between FeOx and Pt nanoparticles. In this case, the catalytic redox cycle in the active Fe3+ sites (mainly for O2 activation) could be easily achieved by the addition of H2O, which finally results in the significant improvement of the activity and stability of the Pt/FeOx catalyst in low-temperature oxidation of CO.