Influence of Dihydrogen and Water Vapor on the Kinetics of CO Oxidation over Au/Al₂O₃

Alumina-supported Au nanoparticles were prepared by a deposition-precipitation method using HAuCl 4 and a thermal treatment in He. X-ray absorption spectroscopy at the Au L III edge revealed that the Au particles were predominantly metallic with an average size of 1.2 nm. The kinetics of CO oxidation were measured with various amounts of co-fed H 2 O in the presence and absence of H 2 . Co-feeding H 2 O significantly increased the rate of CO oxidation, with rates similar to that observed during selective CO oxidation in H 2 . The order of reaction with respect to CO decreased from 0.32 to 0.18 by the addition of water vapor. In contrast, the O 2 order increased from 0.36 to 0.48 in the presence of H 2 O. The temperature dependence of the rate changes with water concentration. Although values of the kinetic parameters determined in the presence of H 2 were different from those in the presence of co-fed H 2 O, the general trends were similar. These results suggest that the presence of H 2 O or H 2 and O 2 have similar promotional effects during CO oxidation on Au/Al 2 O 3 .