Promotional effect of H2 on CO oxidation over Au/TiO2 studied by operando infrared spectroscopy

The oxidation of carbon monoxide in the presence of various concentrations of molecular hydrogen has been studied over a Au/TiO2 reference catalyst by combining diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and mass spectrometry. It is shown for the first time that H2 enhances the CO oxidation rate on Au/TiO2 without leading to any major loss of selectivity. Increasing the H2 pressure induces higher CO and H2 oxidation rates. Under H2-free conditions, the surface species detected are Auδ+–CO, Ti4+–CO, carbon dioxide and carbonates. Upon the addition of H2, Au0–CO, water and hydroxyl groups become the main surface species. The occurrence of a preferential CO oxidation mechanism involving HxOy species under the present experimental conditions is proposed.