采用基于密度泛函理论的第一原理计算方法,研究了氢分子(H2)在清洁、空位缺陷及Pd原子吸附的Mg(0001)表面的吸附与解离性能.结果显示:H2在清洁Mg(0001)表面呈较弱的物理吸附,H2解离需克服较高的能垒(1.3774 eV);空位缺陷的存在增强了Mg表面对H2的物理吸附能力,且使H2的解离能垒(1.2221 eV)有所降低;而清洁表面吸附的Pd原子则会与H2产生强烈的化学吸附作用,极大地降低了H2的解离能垒(0.2860 eV).电子结构分析发现:3种表面对H2吸附与解离的催化活性与Mg(0001)表面最上层与H2直接产生吸附作用的金属原子在费米能级(EF)附近s轨道的成键电子数密切相关.
By the first-principles calculations method based on the density functional theory, H2 adsorption and dissociation properti-es on clean, vacancy defective and Pd atom coadsorption Mg(0001) surfaces are investigated systematically. The calculation results show that the model of H2 adsorption on clean surface is weak physisorption, and there is a high energy barrier, i.e., 1.3774 eV, when H2 dissociates into two separate H atoms. Vacancy defect not only benefits enhancing of the physisorption interaction between H2 and Mg surface, but also decreasing of the energy barrier, i.e., 1.2221 eV, of H2 dissociation to some extent. For Pd atom coadsorp-tion Mg(0001) surface, there is a strong chemisorption interaction between Pd atom and H2, and the energy barrier, i.e., 0.2860 eV, of H2 dissociation is reduced significantly. Further analysis of electronic structures shows that the catalytic activity for H2 adsorption and dissociation on three different surfaces is closely related to the bonding electrons number of s orbital of the topmost layer metal atoms which interact directly with H2 around Fermi level.
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