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Using density functional theory (DFT) calculations and Rietveld simulations and refinement, the structural identification and atomic position of rutile-type IrO2 bulk are determined. Our simulated x-ray diffraction is showed in good agreement with previous experimental data by Natl. et al. 1 Based on the Rietveld-refined model, the absorption and reaction of CO and O2 molecules on the IrO2 (110) surface are investigated. The adsorption of carbon monoxide is exothermic by 2.05 eV for the C end-on above the Ircus atoms. Whereas, the adsorption of oxygen molecule leads to a 2η-O2 chemisorbed structure, bridging two neighboring Ircus atoms and weakly
held O atoms in terminal position above the Ircus atoms, and the adsorption energy is 1.74 eV. The CO molecule can be oxidized by different oxygen species on the surface. The calculated results demonstrate the CO oxidation by Otop and 1η-O2 have almost the same barrier, ~ 0.63 eV, and the latter has much larger exothermic reaction energy. While, the CO oxidation by Obr atom is endothermic and has higher barrier.
Keywords: IrO2, DFT, CO, Oxygen, Rietveld-refined model
Reference:
1. JCPDS card no. 15-0870 (IrO2), International Centre for Diffraction Data Newtown Square, PA, USA.
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