摘要
采用密度泛函理论(Density Functional Theory DFT)研究Au(100)和Au(111)表面含有不同Pd构型时表面的形成能.结果表明,非连续Pd构型的形成能较连续Pd构型的低,在表面易形成,其中第二临位Pd对构型被证实是乙烯与醋酸结合生成醋酸乙烯反应中催化活性最高的构型.随后计算CO在不同表面Pd原子的顶位吸附能和Pd原子的d带中心,结果显示表面Pd原子与相邻金原子之间几乎没有电子传递,并且PdAu(111)表面的Pd原子d带中心随周围Au原子个数的增加而远离费米能级,伴随着CO在其上吸附能的减小,但是同样的趋势在PdAu(100)表面不存在.最后,通过计算,CO在金属表面的吸附机理为CO成键轨道5σ的电子传递给Pd原子的d带,而Pd原子的d带电子又反馈回CO的反键轨道2π*.
Density Functional Theory （DFT） was carried out to calculate the formation energy of different ensem- bles in Au（100） and Au（ 111 ） surfaces. The ensembles of noncontinous Pd atoms were found to be more energy- stable than continuous configurations on surfaces, and the second neighbor Pd pair was the most active sites for syn- thetizing vinyl acetate. The adsorption energy of CO on atop site and d band center of Pd in different ensembles were also investigated to research the synergistic effect between Pd and Au. The results showed that there was little electron transfer between Pd atoms and adjacent Au atoms on both surfaces and d band center and adsorption energy of CO decreased with the increasing number of Au atoms around Pd atoms in PdAu（lll ） surfaces, which didn＇t exist in PdAu（100） surfaces. Finally, the mechanism of CO-metal interaction can be considered as donation from the CO-5σ state to metal and back donation from metal to the CO-2π＊ state.
出处
《分子催化》
EI
CAS
CSCD
北大核心
2013年第1期63-69,共7页
Journal of Molecular Catalysis(China)
