Atmospheric-Pressure Cold Plasma Activating Au/P25 for CO Oxidation: Effect of Working Gas

Commercial TiO₂ (P25) supported gold (Au/P25) attracts increasing attention. In this work, atmospheric-pressure (AP) cold plasma was employed to activate the Au/P25-As catalyst prepared by a modified impregnation method. The influence of cold plasma working gas (oxygen, argon, hydrogen, and air) on the structure and performance of the obtained Au/P25 catalysts was investigated. X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM), and X-ray spectroscopy (XPS) were adopted to characterize the Au/P25 catalysts. CO oxidation was used as model reaction probe to test the Au/P25 catalyst. XRD results reveal that supporting gold and AP cold plasma activation have little effect on the P25 support. CO oxidation activity over the Au/P25 catalysts follows the order: Au/P25-O₂P > Au/P25-As > Au/P25-ArP ≈ Au/P25-H₂P > Au/P25-AirP. Au/P25-AirP presents the poorest CO oxidation catalytic activity among the Au/P25 catalysts, which may be ascribed to the larger size of gold nanoparticles, low concentration of active [O]_s, as well as the poisoning [NO_x]_s. The poor catalytic performance of Au/P25-ArP and Au/P25-H₂P is ascribed to the lower concentration of [O]_s species. 100% CO conversion temperatures for Au/P25-O₂P is 40 °C, which is 30 °C lower than that over the as-prepared Au/P25-As catalyst. The excellent CO oxidation activity over Au/P25-O₂P is mainly attributed to the efficient decomposition of gold precursor species, small size of gold nanoparticles, and the high concentration of [O]_s species.