Gold nanoparticles supported on manganese oxides for low-temperature CO oxidation

A series of gold catalysts deposited on various single-phase manganese oxides (MnOx, including MnO2, Mn2O3 and Mn3O4) were studied in relation to their performance in the low-temperature oxidation of CO. Gold was deposited onto the MnOx support by deposition–precipitation with urea (DP urea). The activity of the Au/MnOx catalysts for CO oxidation strongly depends on the nature of the manganese oxide support, ranking in the order Au/Mn2O3 > Au/MnO2 > Au/Mn3O4. Transmission electron microscopy (TEM) results revealed different particle size distributions of gold for these Au-based catalysts, among which the Au/Mn2O3 catalyst showed the highest gold dispersion. Temperature programmed reduction (TPR) experiments indicated that the reducibilities of Au/MnOx catalysts follow the same sequence with the activity. X-ray photoelectron spectroscopy (XPS) results suggested that both metallic and cationic gold species existed in the Au/Mn2O3 catalyst, while only metallic gold species were present in the other catalysts. The unique surface redox properties of Mn2O3 show great superiority for anchoring and dispersing of gold nanoparticles, which in turn leads to a higher reducibility of Mn2O3 and activity of the Au/Mn2O3 material for CO oxidation.