A DFT Investigation of the γ-Al_2O_3 Supported Fe_3Zn and Fe_4 Clusters as Catalysts for CO_2 Adsorption and Activation

摘要

The synergy between different components in a multicomponent catalyst has been exploited in many important catalytic processes, including CO_2 conversion and utilization. In the present work, the clusters Fe_4 and Fe_3Zn supported on γ-Al_2O_3 have been studied for CO_2 adsorption and activation using density functional theory slab calculations. Our results indicated that γ-Al_2O_3 induces charge redistribution in the supported clusters, resulting in Fe~(δ+) and Fe~(δ-) sites. This charge redistribution is believed to be the origin of the experimentally observed promotion effect of γ-Al_2O_3 toward CO_2 conversion. Furthermore, we found that the tetrahedral configuration of Fe_4 and F_3Zn is stabilized by the strong metal-support interaction to a larger degree than the planar configuration. Upon CO_2 adsorption and activation, the metal atoms of the supported cluster are all oxidized as indicated by the electron transfer from cluster to the adsorbed CO_2. Our study showed that the incorporation of Zn in the cluster modified both the geometrical and electronic properties of the Fe-based catalyst.