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

The mechanism of H 2 dissociation on supported gold catalysts was investigated due to their wide applications in hydrogenation reactions. The analysis of Hückel theory suggests O 2– –H + –H – –Au as a transition-state structure for H 2 dissociation on a Au/TiO 2 system because of strong O 2– –H + interaction. Subsequent density-functional theory (DFT) calculations verified that the O 2– –H + –H – –Au structure at the perimeter of Au/TiO 2 displays the lowest reaction barrier for H 2 dissociation among various surface sites of gold, TiO 2, and Au/TiO 2 systems. In addition, the dissociation barrier on this O 2– –H + –H – –Au structure is dependent on the charge on oxygen; TiO 2 -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 TiO x /Au system should be less active due to more electrons on oxygen, which can explain recent experimental results.