摘要
采用广义梯度密度泛函理论研究了0.25ML覆盖度下CO_2在α-U(001)表面上的吸附和解离,得到了CO_2的稳定吸附构型和吸附能,确定了CO_2的解离过渡态和解离能垒,探讨了CO_2与表面U原子的相互作用本质.结果表明CO_2趋向以C(O)-U多键结合方式在α-U(001)面发生强化学吸附,吸附能为1.24-1.67 eV;C-O键的活化程度依赖于表面电子向CO_2发生转移的程度.CO_2与表面U原子的相互作用主要来自于U原子电子向CO_2最低空轨道(LUMO)2π_u转移,以及CO_2π_u/1π_g/3σ_u-U 6d轨道间杂化而生成新的化学键.以形成3个C-U键和6个O-U键模式在穴位1和穴位2上发生吸附的CO_2(H1-C_3O_6和H2-C_3O_6)的解离吸附能分别为3.15和3.13 eV,解离能垒分别为0.26和0.36 eV,预示着吸附CO_2分于易于解离形成CO分子和O原子.
The adsorption and dissociation of CO2 on the α-U（001） surface at 0.25 monolayer （ML） coverage was studied using density functional theory （DFT） within the generalized gradient approximation （GGA）, Stable structures and corresponding energies of CO2 adsorbed on the α-U（001） surface were obtained while the transition state and corresponding energy barrier for CO2 dissociation was determined. We discussed the interaction mechanism between CO2 and the α-U（001） surface. We found that CO2 strongly chemisorbed onto the α-U（001） surface in a multi-bonding manner with adsorption energies of 1.24-1.67 eV and the degree of C-- O bond activation depended on the degree of electron transfer from surface to the adsorbed CO. The interaction between the U atoms and the CO2 molecules mainly comes from the population of the CO2 2πu lowest unoccupied molecular orbital （LUMO） by U electrons with CO2 2πu/1πg/3σ-U 6d orbital hybridization. The dissociative adsorption energies for the CO2 adsorbed on the hollow1 and hollow2 sites with three C-- U bonds and six O-- U bonds （H1-C3O6 and H2-C3O6 ） are 3.15 and 3.13 eV, respectively. The corresponding dissociation barriers are 0.26 and 0.36 eV, which indicates that the dissociation of adsorbed CO2 into CO and O occurs easily.
出处
《物理化学学报》
SCIE
CAS
CSCD
北大核心
2011年第10期2319-2325,共7页
Acta Physico-Chimica Sinica
基金
国防科技重点实验室基金(9140C6601010901)
中国工程物理研究院科学技术基金(2008A0301013)资助项目~~
