标题：Surface dependence of CO _2 adsorption on Zn _2GeO _4
作者：Liu, L.;Fan, W.;Zhao, X.;Sun, H.;Li, P.;Sun, L.
作者机构：[Liu, L] State Key Laboratory of Crystal Materials, Shandong University, Jinan, 250100, China;[ Fan, W] Department of Chemistry and Chemical Engineeri 更多
通讯作者地址：[Fan, WL]Shandong Univ, State Key Lab Crystal Mat, Jinan 250100, Peoples R China.
来源：Langmuir: The ACS Journal of Surfaces and Colloids
摘要：An understanding of the interaction between Zn _2GeO _4 and the CO _2 molecule is vital for developing its role in the photocatalytic reduction of CO _2. In this study, we present the structure and energetics of CO _2 adsorbed onto the stoichiometric perfectly and the oxygen vacancy defect of Zn _2GeO _4 (010) and (001) surfaces using density functional theory slab calculations. The major finding is that the surface structure of the Zn _2GeO _4 is important for CO _2 adsorption and activation, i.e., the interaction of CO _2 with Zn _2GeO _4 surfaces is structure-dependent. The ability of CO _2 adsorption on (001) is higher than that of CO _2 adsorption on (010). For the (010) surface, the active sites O _2c ?Ge _3c and Ge _3c-O _3c interact with the CO _2 molecule leading to a bidentate carbonate species. The presence of Ge 3c-O 2c ?Ge _3c bonds on the (001) surface strengthens the interaction of CO _2 with the (001) surface, and results in a bridged carbonate-like species. Furthermore, a comparison of the calculated adsorption energies of CO _2 adsorption on perfect and defective Zn _2GeO _4 (010) and (001) surfaces shows that CO _2 has the strongest adsorption near a surface oxygen vacancy site, with an adsorption energy -1.05 to -2.17 eV, stronger than adsorption of CO _2 on perfect Zn _2GeO _4 surfaces (E _(ads) = -0.91 to -1.12 eV) or adsorption of CO _2 on a surface oxygen defect site (E _(ads)) = -0.24 to -0.95 eV). Additionally, for the defective Zn _2GeO _4 surfaces, the oxygen vacancies are the active sites. CO _2 that adsorbs directly at the Vo site can be dissociated into CO and O and the Vo defect can be healed by the oxygen atom released during the dissociation process. On further analysis of the dissociative adsorption mechanism of CO 2 on the surface oxygen defect site, we concluded that dissociative adsorption of CO 2 favors the stepwise dissociation mechanism and the dissociation process can be described as CO _2 + Vo → CO _2 ~(δ-)/Vo → CO _(adsorb