摘要
采用密度泛函理论(DFT)计算了Pd(111)表面含有N(N=1-4)个Au原子数目时的表面形成能,选取最优构型进一步研究了噻吩在Au/Pd(111)双金属表面的吸附模式及加氢脱硫反应过程.结果表明:当Pd(111)表面含有1个Au原子时,其形成能最低.在Au/Pd(111)双金属表面噻吩初始吸附于Pd-Hcp-30°位时,其构型最稳定.在各加氢脱硫过程中,反应总体均放出热量.对于直接脱硫机理,其所需活化能较低,但脱硫产物较难控制;对于间接脱硫机理,反应最有可能按照顺式加氢方式进行,C―S键断裂开环时所需活化能最高,是反应的限速步骤.此外,与单一Au(111)面及Pd(111)面相比,Au/Pd(111)双金属表面限速步骤的反应能垒最低,表明AuPd双金属催化剂比Au、Pd单金属催化剂更有利于噻吩加氢脱硫反应的进行.
The formation energy of different ensembles on Pd（111） surfaces containing N （N=1-4） Au atoms were investigated using a density functional theory model. The best model for exploring the adsorption of thiophene was selected, and the mechanism of competitive hydrodesulfurization on a Au/Pd（111） bimetallic surface was investigated. The results showed that Au/Pd（111 ） has the lowest formation energy, and adsorption at the hexagonal close-packed site is most stable when the thiophene plane is tilted at 30°to the Au/Pd（111） bimetallic surface with S atom. The reactions are exothermic, and desulfurization can be either direct or indirect. The direct desulfurization pathway has a low activation energy, but it is difficult to control the products. The indirect desulfurizaUon pathway is the best fit for the cis-hydrogenation process; C--S cleavage has the highest reaction energy barrier, and is the rate-determining step. The activation energy barrier of the rate-determining step on Au/Pd（111 ） is lower than those on Au（111 ） and Pd（111 ）. This indicates that bimetallic AuPd is more active than single Au and Pd in the hydrodesulfurization of thiophene.
出处
《物理化学学报》
SCIE
CAS
CSCD
北大核心
2014年第10期1847-1854,共8页
Acta Physico-Chimica Sinica
