Chemical reactivity of O2, CO and CO2 on Cu surfaces

Zhang, D.

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 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...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).
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Chemical reactivity of O2, CO and CO2 on Cu surfaces