不同金属催化水煤气变换反应活性的DFT研究  

DFT STUDIES OF ACTIVITY OF WATER GAS SHIFT REACTION BY SEVERAL METALS CATALYZED

作　　者：赵国利[1] 刘丹[1] 刘实[1] 张晓彤[1] 桂建舟[1] 孙兆林[1] 

机构地区：[1]辽宁石油化工大学石油化工学院,辽宁抚顺113001

出　　处：《石油化工高等学校学报》2005年第2期19-22,共4页Journal of Petrochemical Universities

基　　金：国家自然科学基金资助项目 (2 0 3430 0 6 )。

摘　　要：采用密度泛函理论(DFT)对水煤气变换反应中的CO分子在M (10 0 ) (M代表Cu、Ag、Au、Pd和Pt)表面上的吸附行为和吸附在金属表面上的H2 O分子的解离过程进行了研究。计算结果表明,CO在金属表面吸附后,C─O键长均在0 .114 3～0 .116 0nm (气相为0 .112 8nm)内,C─O键都不同程度地伸长了,表明它们削弱了C─O键,活化了CO分子。在对C─O键长、表面结合能(EB)、电子集居数等的分析中得到各表面对CO的吸附强度以Pd(10 0 )、Pt(10 0 )、Cu(10 0 )、Ag(10 0 )、Au(10 0 )顺序减弱;同时将此表面结合能、d电子转移数分别与水煤气变换反应的活性数据进行了关联,说明铜具有最好的活化性能。通过对水分子在不同金属表面上的解离过程的活化能研究发现,各表面对应的能量势垒以Au(10 0 )、Pt(10 0 )、Ag(10 0 )、Pd(10 0 )、Cu(10 0 )顺序下降,从而进一步解释了金属铜的催化活性优于其它金属催化剂的原因,此结论与实验结果相符。The difference in adsorption for CO on the M(100) (M denotes Cu, Ag, Au, Pd and Pt) surfaces and the H2O activation energies of the dissociations on the surfaces were investigated by first-principle density functional theory. The calculation results show that C-O bond distance is 0.1143-0.1160 nm (compared to 0.112 8 nm in the gas phase) and demonstrate C-O bond is weakened and CO is activitied after adsorption. CO bond distance, bind energy analysis and Miilliken population analysis of CO/M(100) adsorption systems were calculated by DFT method. It can be concluded from the analyzed results that the absorbability of CO decreases in the order of Pd(100), Pt(100), Cu(100), Ag(100) and Au(100). The implications of these results in terms of the catalysis of the water gas shift (WGS) reaction were discussed. From the volcano-shaped relationship between metal turnover number and bind energy of carbon monoxide and the electron transfer number of d orbital, it can be easily concluded that copper may be the optimum reactivity component of the catalyst in corresponding to the WGS reaction. By comparison the activation energies difference of an important elementary step in surface redox mechanism over different metals, it was found that the activity energy decreases in the order of Au(100), Pt(100), Ag(100), Pd(100) and Cu(100), which further consolidates the conclusion. Calculations agree well with the experimental values and may explain the reason why copper is more activitive than other metals in a qualitative view.

关 键 词：一氧化碳 过渡金属 吸附 模拟 水煤气变换反应 

分 类 号：O641.12[理学—物理化学]