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Atmospheric Pressure Oxygen Cold Plasma for Synthesizing Au/TiO2 Catalysts: Effect of Discharge Voltage and Discharge Time

Atmospheric pressure (AP) oxygen cold plasma was adopted to synthesize Au/TiO2 catalysts with the assistance of a simple modified incipient wetness impregnation process. Discharge voltages of 25.0, 29.0, and 35.0 kV and discharge time of 1, 2, and 4 min are selected to investigate the effects of discharge voltage and discharge time on the property of the Au/TiO2 catalysts. The results of carbon monoxide (CO) oxidation activity testing show that AP oxygen cold plasma is beneficial to enhance the activity of the Au/TiO2 catalysts, and the optimal discharge voltage and time are 29.0 kV and 1 min, respectively. CO conversion of the Au/TiO2-29-1 catalyst at 30 °C is 1.42 times as that of the Au/TiO2-As catalyst without plasma treatment. The UV-Vis diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy characterizations indicate that AP oxygen cold plasma not only can decompose the gold species formed by the modified impregnation process to form metallic gold species but also can remove some of the oxygen species on the surface of the TiO2 support. The discharge time of 1 min at 29.0 kV is enough to decompose the gold species formed by the modified impregnation process, and to keep much active hydroxyl groups. Moreover, there is little difference in the size of gold nanoparticles in the Au/TiO2 catalysts. Therefore, Au/TiO2-29-1 catalyst exhibits higher CO oxidation activity than Au/TiO2-As, and 1 min is the optimal discharge time. Thanks to the AP oxygen cold plasma method, high-performance Au/TiO2 catalysts can be synthesized simply in a short time.