Ru修饰前后Pd(111)面的性质及对糠醛吸附的比较研究

采用密度泛函理论研究了Pd(111)面和Ru-Pd(111)面的性质及对糠醛的吸附.原子尺寸因素、相对键长、形成能及d带中心等计算结果表明,Ru-Pd(111)面比Pd(111)面稳定且活性强,Ru的修饰优化了Pd(111)面的几何构型.糠醛在Pd(111)面及Ru-Pd(111)面的初始吸附位分别为P(top-bridge)位及P(Pd-fcc-Ru-fcc)位时,吸附能最大,吸附构型最稳定.由电荷布局和差分电荷密度可得,糠醛在Ru-Pd(111)面上电荷转移数更多,相互作用更强烈,因此吸附能更大.分析态密度可知,产生吸附的主要原因是位于-7.34 eV处至费米能级处的p,d轨道杂化.吸附于Ru-Pd(111)面后糠醛分子的p轨道向低能级偏移程度更明显,使Ru改性后的Pd催化剂具有更好的催化活性.

Comparative Study on the Properties and Adsorption of Furfural of Pd( 111) Surface Before and After Ru Modification

The properties of Pd(111), Ru-Pd(111) surfaces and their adsorption of furfural were investiga-ted via periodic density functional theory( DFT) calculations. The results of atomic size factor, relative bond length, formation energy and d-band center showed that Ru-Pd(111) surface was more stable and active than Pd( 111 ) , Ru modification could improve the geometric configuration. For the adsorption of furfural on Pd(111) and Ru-Pd(111) surfaces, the results showed that when the initial adsorption at P(top-bridge) or P(Pd-fcc-Ru-fcc) site, the adsorption energy was the highest and the adsorption configuration was the most stable. After analyzing Mulliken atomic charge population and the deformation density, it was found that for the adsorption of furfural on Ru-Pd(111) surface, the number of charge transferred was more and the interaction was stronger, therefore it' s adsorption energy was higher. The result of state density indicated that the main reason for the adsorption was that the p and d orbitals hybridization existed at-7. 34 eV relative to Fermi level. Meanwhile, the p-orbital of furfural shifted to the low-level was more obvious on Ru-Pd(111) surface, so Pd catalyst after Ru modification had better catalytic activity.