Ab Initio Study of the Use of Ag2- for Catalytic Oxidation of CO.

The formalisms of density functional theory with Perdew and Wang exchange-correlation functional have been employed to study the electronic and geometric structures of silver anion dimer bonded with carbon monoxide and oxygen. Different possible structures for Ag$_{2}$O$_{2}^{-}$ and Ag$_{2}$CO$^{-}$ have been investigated in detail. An all electron 6-311++G** basis set for carbon and oxygen and a pseudopotential basis set for silver have been used for performing the calculations using the Gaussian 03 suite of programs.$^{1}$ Using Ag$_{2}^{-}$ as a catalyst, a full catalytic cycle producing two CO$_{2}$ molecules will be presented. Also, presence of an intermediate state, Ag$_{2}$CO$_{3}^{-}$, which can be detected experimentally, is predicted. Presence of an energy barrier for certain reactions from the catalytic cycle has \textit{not} been observed. This is noteworthy since it has been claimed in the literature that for the same catalytic cycle to proceed using Au$_{2}^{-}$ as a catalyst, it has to overcome an energy barrier. Charge state effects have been studied by following similar steps for the catalytic cycle using the Ag$_{2}^{+}$ and Ag$_{2}$ as catalysts. We conclude that the Ag$_{2}^{-}$ performs better as a catalyst compared to the Ag$_{2}^{+}$ and Ag$_{2}$. \textbf{*}Work supported, in part, by the Welch Foundation, Houston, Texas (Grant No. Y-1525). $^{1 }$\textit{Gaussian 03, }M. J. Frisch \textit{et al., }Gaussian Inc., Pittsburgh, PA.