A density functional study for adsorption and oxidation of NO on Ir (1 0 0) surface

Density functional theory (DFT) calculations are used to investigate the adsorption of nitrogen oxides (NOx) (x = 1, 2) and oxidation reaction on Ir (1 0 0) surface. On clean surface, NO molecule energetically prefers to bond at bridge sites for all studied coverages (Θ = 0.25, 0.50, 0.75 and 1.00) monolayer (ML). An electron donation from the occupied orbitals to the d metal band and a back donation from the substrate to the 2π* orbital occur for adsorbed NO on Ir (1 0 0) surface, which causes an increase in NO bond. NO2 molecule exhibits a variety of adsorption geometries; the most energetically favorable is the μ-N,O-nitrito configuration with an adsorption energy 1.91 eV. The reaction pathway and the transition state (TS) are determined using constrained minimization method. At the TS, the adsorbed oxygen (Oa) atom and NO molecule diffuse to less stable states (top). Then they react to form chemisorbed NO2 with activation energy about 1.41 eV.

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► We used DFT to investigate the adsorption of nitrogen oxides on Ir (1 0 0).
► We used constraint minimization method to study oxidation reaction of NO on Ir (1 0 0).
► NO prefers to bond at bridge site on Ir (1 0 0) for all the studied coverages.
► The most stable configuration for NO2 adsorbed on Ir (1 0 0) is μ-N,O-nitrito.
► Oxidation of NO on Ir (1 0 0) surface leads to adsorbed NO2 molecule.