Fundamental Studies of Alcohol Reactions on Gold and Copper

Abstract

The thesis has focused on revealing the mechanistic insights of the gaseous alcohol coupling/dehydrogenation/oxidation reactions for selectively making value-added products on the solid gold/copper single-crystal surfaces under ultrahigh vacuum (UHV) conditions. Those molecular-level insights about the selectivity, reactivity, and kinetics of metal-based heterogeneous catalysis, combined with density functional theory (DFT) calculations and ambient-pressure studies, provided guiding principles for the rational design of efficient real-life catalysts, which are crucial for a sustainable future. First, the background of gold/copper-based catalysis and the motivation of UHV model studies were discussed (Chapter 1). Relative binding strengths of intermediates on a catalyst surface govern the competition for the reactive sites and thus the overall reaction selectivity. The critical contribution of the noncovalent van der Waals (vdW) interactions to alkoxys’ overall binding strengths was revealed on both gold (Chapter 2) and copper (Chapter 5) combining experiment and theory. Similar results on two metals suggest the generality of such effect on metal-based catalysts. Then, kinetic parameters were measured for the gaseous alcohol reactions on Au(110) using temperature-programmed reaction/desorption (TPR/TPD) studies (Chapter 3). Next, the structure-dependent reactivity of methanol and ethanol with surface atomic oxygen as active sites on Au(110) was revealed combining TPR/TPD and scanning tunneling microscopy (STM) (Chapter 4). Furthermore, the critical role of defects as the active sites for the gaseous alcohol dehydrogenation reactions on Cu(111) and Cu(110) was studied using TPR/TPD and STM (Chapter 6). Detailed quantification of the defect active sites was discussed subsequently (Chapter 7). Finally, the methods used in this work were described (Chapter 8). Chapters 2-4 are about the research on gold and Chapters 5-7 are about the research on copper.