The catalytic mechanism of CO oxidation in AlAu6 clusters determined by density functional theory

Abstract

We present density functional calculations of O₂ and CO adsorption on an AlAu₆ cluster. It is found that in the AlAu₆ cluster the active sites would be first occupied by coming O₂ rather than CO due to a more negative binding energy of the former. Furthermore, the catalytic mechanisms of CO oxidation in AlAu₆ clusters, which are based on a single CO molecule and double CO molecules, are discussed. This investigation reveals that the reaction of a single CO molecule with the AlAu₆O₂ complex has the lowest activation barrier (0.27 eV), which is 0.51 eV lower than that of the pure Au₆⁻ cluster. For the AlAu₆O₂(CO)₂ complex, due to the structural distortion of the AlAu₆ cluster, the activation barrier of the determination rate is higher by 0.53 eV than that of the AlAu₆O₂CO complex, which shows that the cooperation effect of the second CO molecule can go against CO oxidation. For the Al@Au₆O₂(CO)₂ complex, the activation barrier of the determination rate is lower by 0.07 eV than the path of one CO molecule, which demonstrates that the cooperation effect of the second CO molecule can prompt CO oxidation.