CO在某些过渡金属表面吸附活化的DFT研究

采用DFT方法对CO在M(100)(M= Cu、Ag、Au、Pd、Pt)表面上的吸附行为进行了系统的比较性研究.结果表明,CO分子在这些过渡金属单晶表面上发生的是非解离性吸附,吸附后C－O键长都变长了,均不同程度地削弱了C－O键,继而活化了CO分子；从表面结合能、重叠集居数、轨道电子数变化等方面分析了成键强弱顺序,发现CO的吸附强度随Pd(100)、Pt (100)、Cu (100)、Ag(100)、Au(100)顺序依次减弱,并且将CO与过渡金属间的结合能(BE)、过渡金属的d电子转移数分别与水煤气变换反应活性数据进行了关联,在定性上比较好地解释了金属铜的催化活性优于其它金属的原因.

DFT Studies of CO Adsorption and Activation on Some Transition Metal Surfaces

The difference in adsorption for CO on the M(100) (M= Cu, Ag, Au, Pd, Pt) surfaces has been systematically investigated by first-principle density functional theory. The results indicate that the chemisorption of CO on these transition metal surfaces belongs to non-dissociative adsorption. The increased theoretical CO bond length of 0.1154～0.1161 nm (compared to 0.1128 nm in the gas phase) demonstrates the activation of the CO bond. We have carried out binding energy analysis, a natural bond orbital analysis and Mülliken population analysis of CO/M(100) adsorption systems. It can be concluded from the analyzed results that the adsorbability of CO decreases in the order of Pd(100),Pt(100),Cu(100),Ag(100) and Au(100).We have also discussed the implications of these results in terms of the catalysis of the water gas shift (WGS) reaction. From the volcano-shaped relationship between metal turnover number at 300 ℃ and binding energy of carbon monooxide and the electron transfer number of d orbital, it can be found that copper may be the optimum reactivity component of the catalyst in corresponding to the WGS reaction. Our calculations agree well with the experimental values and may explain the reason why copper is more activitive than other metals in a qualitative view.