Does Symmetry Control Photocatalytic Activity of Titania-Based Photocatalysts?

Decahedral anatase particles (DAPs) have been prepared by the gas-phase method, characterized, and analyzed for property-governed photocatalytic activity. It has been found that depending on the reaction systems, different properties control the photocatalytic activity, that is, the particle aspect ratio, the density of electron traps and the morphology seem to be responsible for the efficiency of water oxidation, methanol dehydrogenation and oxidative decomposition of acetic acid, respectively. For the discussion on the dependence of the photocatalytic activity on the morphology and/or the symmetry other titania-based photocatalysts have also been analyzed, that is, octahedral anatase particles (OAP), commercial titania P25, inverse opal titania with and without incorporated gold NPs in void spaces and plasmonic photocatalysts (titania with deposits of gold). It has been concluded that though the morphology governs photocatalytic activity, the symmetry (despite its importance in many cases) rather does not control the photocatalytic performance.

The catalytic activity of PtnCum (n+m=3, m≠3) clusters for methanol dehydrogenation to CO

Based on the density functional theory (DFT), the geometric for the reactants, intermediates, transition states and dehydrogenation products have been optimized. The energy diagrams are drawn out along both the O-adsorption path and H-adsorption path, and the C-H bond scission pathway is energetically more favorable than the O-H bond scission pathway. By calculation, the Pt is the active site in the whole reaction processes, and the barrier energy of the rate-determining step is 11.09 kcal/mol by Pt: Cu=2: 1 which is lower than that of Pt 3 and PtCu 2 . Importantly, it is shown that the complete dehydrogenation product of methanol, CO, can more easily dissociate from PtCu 2 cluster than from Pt 3 cluster. Therefore, Cu doping can promote the catalytic activity of Pt in a certain extent.