Ab initio study of CO adsorption on PdGa(1 1 0)

CO adsorption is analyzed using Density Functional Theory (DFT) calculations. Changes in the electronic structure of PdGa(1 1 0) surface and CO bond after adsorption are addressed. CO is located only on Pd atop geometry with a tilted configuration (9.13° from the perpendicular to the surface) and no interaction with Ga is detected. The Pd–Pd bond strength decreases 54.2% as the new Pd–CO bond is formed. The C–O bond length change less than 1%, compared to the gas phase value, while its bond overlap population decrease 46.2%. The effect of CO is limited to its first Pd neighbor. Analysis of orbital interaction reveals the Pd–CO bond mainly involves s–s and s–p orbitals with less participation of Pd 4d orbitals. The computed CO vibration frequencies after adsorption shows a red shift from vacuum to ward 2013.85 cm−1, which agrees with previous experimental data on PdGa intermetallic.

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► The C–O and Pd–Pd OP decreases while a Pd–C bond is developed.
► No interaction with Ga is detected.
► CO adsorb atop on a Pd atom with a tilt of 9.13° and an energy of −1.42 eV.
► Pd projected DOS shows small shift to lower energies after CO adsorption (0.60 eV).
► IR frequencies for C–O adsorbed presents a red shift that agrees with experiments.