Possible reaction pathway in methanol dehydrogenation on Pt and Ag surfaces/clusters starting from O-H scission: Dipped adcluster model study

The mechanism of the methanol dehydrogenation reaction on a Pt surface has been investigated using the dipped adcluster model (DAM) combined with density-functional theory (DFT) calculations. Starting from O-H bond scission, methanol decomposes to form CO exothermically on the Pt surface, where the Pt-dσ orbital effectively interacts with the O-H antibonding orbital. The donative interaction of the Pt-dσ orbitals was found to be important for catalytic activation on the Pt surface. The reaction pathway starting from C-H bond scission has a larger activation barrier and, therefore, is less kinetically favorable. Electron transfer from the bulk, which is included in the present DAM calculation, plays an important role in the reaction pathway from O-H bond scission, in particular for the dehydrogenation of formaldehyde. On the other hand, the Ag surface has been shown to be effective for formaldehyde synthesis, because formaldehyde desorbs spontaneously from the Ag surface. The present reaction has also been examined and discussed in view of the nanoscale clusters and nanorods.