Origin of the Different Activity and Selectivity toward Hydrogenation of Single Metal Au and Pt on TiO₂ and Bimetallic Au−Pt/TiO₂ Catalysts

To improve the activity of Au/TiO(2) catalysts toward hydrogenation without decreasing chemoselectivity, a number of isolated and supported Au, Pt, and Au-Pt nanoparticles have been investigated by means of density functional theory (DFT) calculations. H(2) dissociation on Pt and Au-Pt nanoparticles is considerably faster than that on Au, because H(2) adsorption on Pt atoms is dissociative and no activation barriers are involved. The high chemoselectivity of Au/TiO(2) catalysts does not exist in Pt/TiO(2) catalysts no matter how small the Pt particles are, but can be preserved in Au-Pt/TiO(2) catalysts if the Au/Pt ratio is high enough as to keep Pt atoms isolated and not at the active metal-support interface.