Saturated adsorption of CO and coadsorption of CO and O2 on AuN− (N=2–7) clusters

Abstract

A first-principles quantum chemistry method, based on the Kohn-Sham density-functional theory, is used to investigate the adsorption of CO and O2 on small gas-phase gold cluster anions. The saturated adsorption of carbon monoxide on gold cluster anions AuN- (N=2-7) is discussed. The adsorption ability of CO reduces with the increase of the number of CO molecules bound to gold cluster anions, resulting in saturated adsorption at a certain amount of absorbed CO molecules, which is determined by geometric and electronic properties of gold clusters cooperatively. The effect of CO preadsorption on the electronic properties of gold cluster anions depends on the cluster size and the number of adsorbed CO, and the vertical detachment energies of CO-adsorbed gold cluster anions show a few changes with respect to corresponding pure gold cluster anions. The results indicate that the impinging adsorption of CO molecules may lead to geometry structure transformation on Au3- cluster. For the coadsorption of CO and O2 on Au2-, Au3- isomers, Au4-, and Au6-, we describe the cooperative adsorption between CO and O2, and find that the O2 dissociation is difficult on gas-phase gold cluster anions even with the preadsorption of CO.

Gas-phase kinetics and catalytic reactions of small silver and gold clusters

“…As a result, the reactivity of even n silver and gold cluster anions toward molecular oxygen is by far superior to that of odd n clusters [17,18,33,40]. Detailed first principles quantum chemical calculations on the bonding of molecular oxygen to negatively charged gold and silver clusters [46,52,[87][88][89] but also to positively charged silver clusters [37,38,90] support this qualitative picture. Besides providing further detailed structural information, one major point of discussion in the theoretical contributions is the question, whether multiple adsorption of oxygen onto the small noble metal clusters might occur.…”

“…If also the assumption is made that the CO binding energies to Au 2 − and Au 3 − are similar, which is very reasonable according to recent theoretical work [46,89,99,108], the ratio of the termolecular rate constants can be calculated [66]:…”

Theoretical study of CO and O2 adsorption and CO oxidation on linear-shape gold molecules (LGMn) (n=2, 4, 8, 16, and 24)

“…Similarly, it is stronger in neutral than anionic state. The previously reported adsorption energies of CO in cationic, neutral, and anionic Au 2 CO complexes are -2.02 eV, 67 (-1.53 eV, 67 -1.108 eV, 69 and (-0.78 eV, 67 -0.97 eV 65 ), respectively, which are 0.3∼0.5 eV smaller than our calculated ones. The adsorption energies previously reported are given by PW91 functional and ours are B3LYP functional.…”

“…For instance, bond order 1 means single bond, 2 means double bond, and so on. In the 65 and this result suggests that the chemical specie is changed. In the O 2 adsorbed structure in each charge state as mentioned above, we check the influence of increase of the number of Au atom in LGM to the adsorption properties in LGM 2 O 2 complex.…”

Analysis of O2 Adsorption Stability and Strength Over Gold Clusters Using DFT and Logistic Regression

“…For example, the experimental studies indicate that Au particles with diameters less than 5 nm dispersed on a support like Al 2 O 3 , ZrO 2 and TiO 2 in the absence or presence of a promoter such as MgO, MnO x , and Fe x O x are highly active for CO oxidation or selective CO oxidation in hydrogen rich streams [14][15][16]. Similarly, there are numerous computational works focusing on adsorption of CO [17,18] or O 2 [19,20] and their reaction [21][22][23][24]. DFT calculations are usually performed using cluster model because it physically suits well to the CO oxidation over Au based catalysts even though these clusters are much larger than those used in DFT calculations.…”