A series of Au/ -TiO2 with various Co/Ti ratios prepared. /TiO2 was prepared by incipient wetness impregnation with aqueous solution of cobalt nitrate. Au catalysts were prepared by deposition-precipitation (DP) method at pH 7 and 338？K. The catalysts were characterized by inductively coupled plasma-mass spectrometry, temperature programming reduction, X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. The reaction was carried out in a fixed bed reactor with a feed containing 1% CO in air at weight hourly space velocities of 120,000？mL/h？g and 180,000？mL/h？g. High gold dispersion and narrow particle size distribution were obtained by DP method. The addition of into Au/TiO2 enhanced the activity of CO oxidation significantly. Au/5%？？ -TiO2 had the highest catalyst among all the catalysts. was mainly in the form of nanosize Co3O4 which could stabilize the Au nanoparticles. donated partial electrons to Au. The interactions among Au, , and TiO2 account for the high catalytic activity for CO oxidation. 1. Introduction Carbon monoxide is a toxic, colorless, and tasteless gas. It can cause human being to die in short time. Low-temperature CO oxidation has been extensively studied because it plays an important role in gas purification in CO2 lasers, CO gas sensors, air purification devices, and removing trace quantity of CO from ambient air in enclosed atmospheres such as submarines and aircrafts [1–3]. When gold is deposited as nanoparticles on metal oxides, it exhibits surprisingly high catalytic activity for CO oxidation at a temperature as low as 100？K. The activity of gold catalysts also depends on support, preparation method and condition. Haruta and coworkers [1–4] found the high activity of supported gold catalysts for low-temperature CO oxidation. It is believed to occur on the metal-support interface. Cobalt oxides are good in removing the CO, , and VOCs in the air. The cobalt oxides have different oxidation states, such as CoO2, Co2O3, Co3O4, and CoO. The Co3O4 and CoO are more stable than the others. For the activity of CO oxidation reaction, the Co3O4 has a higher activity than CoO [5–8]. The Co3O4 has been reported to be an effective catalyst in the oxidation reaction. Furthermore, it has also been used as a support for gold. was reported to be active for CO oxidation, but not very active at room temperature. Although CO oxidation on Au catalysts has been extensively studied [9–13], none the of researchers has used -TiO2 binary oxide as the support. In this
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