Effect of TiO₂ Crystal Phase and Preparation Method on the Catalytic Performance of Au/TiO₂ for CO Oxidation

Abstract

Titania-supported gold nanoparticles exhibit excellent low-temperature carbon monoxide (CO) oxidation activity, which is sensitive to the structure of the TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> support and the preparation method. In this paper, gold catalysts were prepared on TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> with different anatase-to-rutile ratios by the deposition-precipitation method (Au/TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -C) and plasma-assisted deposition-precipitation method (Au/TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -PC). The highest performance for CO oxidation was obtained over Au/TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> for an anatase-to-rutile ratio of 4:6, which may be ascribed to the phase transformation mechanism of TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and the preferential deposition of Au nanoparticles on rutile TiO2 in the deposition-precipitation process. Therefore, enlarged contact surface between the Au nanoparticles and the TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> support was obtained, and more oxygen vacancies may be formed, which are beneficial to CO oxidation. Interestingly, compared with Au/TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -C, Au/TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -PC exhibited enhanced CO oxidation activity. For example, the reaction rate (ξ) at 30 °C for CO oxidation over Au/TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -PC was about 5.8 times greater than that over Au/TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -C for an anatase-to-rutile ratio of about 4:6, which was primarily caused by the more active gold species on the surface of TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> support in Au/TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -PC due to the Coulomb interaction during plasma preparation.