Despite the history of studies on methanol formation from CO2, the dominant elementary reaction steps that constitute the chemical mechanism for this catalyzed process are not determined. Two main... Show moreDespite the history of studies on methanol formation from CO2, the dominant elementary reaction steps that constitute the chemical mechanism for this catalyzed process are not determined. Two main issues may cause doubt about the current level of understanding: 1) the very large difference in the coverage-dependent sticking probabilities for CO2 and CO and unavoidable CO contamination 2) the complex oxidation of the copper surface and unavoidable build-up of a (partial) oxide layer.In this thesis, we studied the sticking probability of O2 on Cu(111) and compared results to previous experimental and theoretical results. The dissociative chemisorption of O2 on Cu(111) is a direct, activated process with a minimum barrier of approximately 100 meV.In an attempt to develop a method that may undeniably quantify the reactivity of CO2 onto clean and H-containing Cu surfaces, we investigated co-adsorbed CO and O on Cu(111) and Cu(211) with RAIRS. Cu(211) oxidizes much more readily than Cu(111). For incomplete oxidation, the system CO adsorbs to small isolated metallic Cu edges and patches. Fully oxidized Cu(211) binds CO but in a rather different form than clean metallic Cu. The vibrational frequency of adsorbed CO is changed as the co-adsorbed O coverage varies on Cu(211). Show less
This thesis uses the surface science approach to address questions regarding the interaction of oxygen with platinum and its subsequent reaction with carbon monoxide. A Pt(111) single crystal... Show moreThis thesis uses the surface science approach to address questions regarding the interaction of oxygen with platinum and its subsequent reaction with carbon monoxide. A Pt(111) single crystal surface is used as a model for the catalyst. Chapter 1 provides an overview of the literature on the subject. The description of employed experimental techniques and their backgrounds are presented in Chapter 2. Chapter 3 discusses the adsorption of oxygen on Pt(111) at various temperatures and its role in the oxidation of carbon monoxide. Chapter 4 gives an atomic scale insight into the reaction between adsorbed oxygen and carbon monoxide for different ratios of oxygen and carbon monoxide pressures. In Chapter 5, the reaction between CO and oxygen on Pt(111) was used to register noise in tunneling current due to diffusion and recombination of molecules on the catalytically active surface, to draw conclusions on the most likely rate-limiting step in the process Show less
The formation of snow and ice has always intrigued humans and challenged them to study these phenomena. Every snowflake has its own unique history of formation, but no two are alike. Like snow... Show moreThe formation of snow and ice has always intrigued humans and challenged them to study these phenomena. Every snowflake has its own unique history of formation, but no two are alike. Like snow-crystals, interstellar ices consist predominantly of water (H2O), but also contain significant fractions of other molecules such as carbon monoxide (CO), carbon dioxide (CO2), and methanol (CH3OH), and traces of dinitrogen (N2) and ammonia (NH3). The presence, or absence, of a molecule in the ice strongly depends on the environmental conditions. Vice versa, these molecules have an influence on their environment as well. Hence, the chemical composition and the structure of interstellar ices are thought to contain valuable information about the past and the future of interstellar regions, and it is for this reason that interstellar ices are simulated and studied under laboratory conditions. The present thesis contains a study of laboratory analogs of interstellar ices and presents a newly developed apparatus that provides a novel laboratory route to investigate the properties of these ices in more detail than has previously been possible. Show less
