A Study on the Mechanism for H2 Dissociation on Au/TiO2 Catalysts

Abstract

The mechanism of H2 dissociation on supported gold catalysts was investigated due to their wide applications in hydrogenation reactions. The analysis of Huckel theory suggests O2––H+–H––Au as a transition-state structure for H2 dissociation on a Au/TiO2 system because of strong O2––H+ interaction. Subsequent density-functional theory (DFT) calculations verified that the O2––H+–H––Au structure at the perimeter of Au/TiO2 displays the lowest reaction barrier for H2 dissociation among various surface sites of gold, TiO2, and Au/TiO2 systems. In addition, the dissociation barrier on this O2––H+–H––Au structure is dependent on the charge on oxygen; TiO2-surface oxygen, not directly connected to gold, with less electrons leads to a lower barrier, compared to perimeter oxygen connected to gold, and a reduced TiOx/Au system should be less active due to more electrons on oxygen, which can explain recent experimental results.