Surface oxides of Ir(111) prepared by gas-phase oxygen atoms

• Published in: Surface science Vol. 606; no. 23-24; pp. 1965 - 1971
• Main Authors: Chung, Wen-Hung, Tsai, Dah-Shyang, Fan, Liang-Jen, Yang, Yaw-Wen, Huang, Ying-Sheng
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 01.12.2012; Elsevier
• Subjects: Carbon monoxide oxidation; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Iridium single crystal; LEED; Oxidation catalysis; Physics; Surface oxide; Temperature programmed desorption; Iridium single crystal; Carbon monoxide oxidation; Surface oxide; Temperature programmed desorption; LEED; Oxidation catalysis; Oxygen; TDS; Carbon; Monocrystals; Oxidation; Catalysis; Iridium; Gas phase
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/j.susc.2012.08.020

The Ir(111) surface is oxidized with gas-phase oxygen atoms under vacuum condition to achieve an oxidation level beyond its saturation coverage for chemisorption. Two surface oxides, rutile IrO2 of (100) domain and corundum Ir2O3 of (001) domain, have been grown at 550K with different oxygen exposure of 3.6×105L and 7.2×105L respectively. The temperature programmed desorption (TPD) experiment of rutile IrO2(100) shows its desorption curve (at 4Ks−1) peaks at 750K, followed by a long tail of less pronounced desorption features. On the other hand, TPD of corundum Ir2O3(001) displays a symmetric trace, peaking at 880K. Carbon monoxide titration experiments show that adsorbed CO reduces corundum Ir2O3(001) at 400K, but CO does not adsorb on rutile IrO2(100) and no reduction reaction occurs. Evidently, among the two surface oxides, corundum Ir2O3(001) involves in catalysis of carbon monoxide oxidation, while rutile IrO2(100) does not. The formation of two surface oxides is also compared, we conclude that the atom arrangement favors Ir2O3(001) at the oxide/metal interface. ► Ir(111) is oxidized by oxygen atoms beyond the saturated level of chemisorption. ► Rutile IrO2(100) is synthesized at 550K with oxygen exposure 3.6×105L. ► Corundum Ir2O3(001) is synthesized at 550K with oxygen exposure 7.2×105L. ► Corundum surface oxide is reduced by adsorbed CO at 400K, but not rutile.