Catalysis by supported Au catalysts has received extensive investigations, but the relevant fundamental understanding still remains ambiguous. Interestingly, moisture in the feed stream has been unambiguously identified to enhance the activity of supported Au catalysts in low-temperature CO oxidation, but it remains as a challenging issue whether H2O plays a role in the crucial oxygen activation step or not and how.
The group from the University of Science and Technology of China has investigated the effect of NaOH additive on the structure and activity of Au/SiO2 catalysts that is inactive in catalyzing low-temperature CO oxidation, whose results provide unambiguous evidence for the role of surface hydroxyls on Au surfaces in the low-temperature oxygen activation for low-temperature CO oxidation.

　　　
Mechanisms for OH-induced oxygen activation and low-temperature CO oxidation on Au(111) surface

Employing Au/SiO2 inert in catalyzing CO oxidation at temperatures below 150 C, they have successfully elucidated the influence of hydroxyls on the intrinsic activity of Au nanoparticles in CO oxidation both experimentally and theoretically. Hydroxyls can induce the activation of O2 on "inert" Au nanoparticles and thus their activity in catalyzing CO oxidation at room temperature. The DFT theoretical calculation results reveal the determining role of COOH(a) in hydroxyls-induced activation of O2 and catalytic activity of the Au(111) surface in low temperature CO oxidation. di-CO3H(a) whose formation is thermodynamically favorable at low reaction temperatures is identified to be the poison leading to the deactivation of Au/NaOH/SiO2 catalysts in low temperature CO oxidation. These results provide novel insights into the role of hydroxyls in the catalytic activity of Au catalysts and advance the fundamental understanding of oxidation reactions catalyzed by Au catalysts.
The work was published in Journal of Catalysis (2011, 277: 95).