CO oxidation catalyzed by a single gold atom: benchmark calculations and the performance of DFT methods

Abstract

Quantum chemical calculations were carried out on CO oxidation catalyzed by a single gold atom. To investigate the performance of density functional theory (DFT) methods, 42 DFT functionals have been evaluated and compared with high-level wavefunction based methods. It was found that in order to obtain accurate results the functionals used must treat long range interaction well. The double-hybrid mPW2PLYP and B2PLYP functionals are the two functionals with best overall performance. CAM-B3LYP, a long range corrected hybrid GGA functional, also performs well. On the other hand, the popular B3LYP, PW91, and PBE functionals do not show good performance and the performance of the latter two are even at the bottom of the 42 functionals. Our accurate results calculated at the CCSD(T)/aug-cc-pVTZ//mPW2PLYP/aug-cc-pVTZ level of theory indicate that Au atom is a good catalysis for CO oxidation. The reaction follows the following mechanism where CO and O₂ adsorb on Au atom forming an Au(OCOO) intermediate and subsequently O₂ transfer one oxygen atom to CO to form CO₂ and AuO. Then AuO reacts with CO to form another CO₂ to complete the catalytic cycle. The overall energy barrier at 0 K for the first CO oxidation step (Au + CO + O₂ → AuO + CO₂) is just 4.8 kcal mol⁻¹, and that for the second CO oxidation step (AuO + CO → Au + CO₂) is just 1.6 kcal mol⁻¹.