Surface oxides of Ir(111) prepared by gas-phase oxygen atoms |
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Authors: | Wen-Hung Chung Dah-Shyang Tsai Liang-Jen Fan Yaw-Wen Yang Ying-Sheng Huang |
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Affiliation: | 1. Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei, 10607 Taiwan;2. National Synchrotron Radiation Research Center (NSRRC), Hsinchu Science Park, Hsinchu, 30076 Taiwan;3. Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei, 10607 Taiwan |
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Abstract: | 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 550 K with different oxygen exposure of 3.6 × 105 L and 7.2 × 105 L respectively. The temperature programmed desorption (TPD) experiment of rutile IrO2(100) shows its desorption curve (at 4 K s? 1) peaks at 750 K, 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 880 K. Carbon monoxide titration experiments show that adsorbed CO reduces corundum Ir2O3(001) at 400 K, 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. |
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