NiMn双金属与MgO载体间的相互作用对氢气解离的影响

摘要

Density functional theory has been employed to investigate the interaction between NiMn bimetal and MgO support,further to investigate the influence of the interaction on H adsorption and H2 dissociation,and the results were compared with those on Ni/MgO.Two catalyst models,i.e.,perfect and defective MgO supported Ni2Mn2 clusters were built to represent the modeling catalyst.The results show that the interaction of defective MgO and active component Ni2Mn2 is stronger than that between perfect MgO and active component Ni2Mn2,and the adsorption of H on defective Ni2Mn2/MgO is stronger than that on perfective one,and further,H2 dissociation is favorable on defective Ni2 Mn2/MgO compared that on perfect Ni2 Mn2/MgO.Compared to MgO supported Ni4,the addition of a second metal Mn makes the interaction between active component and MgO support decrease,correspondingly,the ability of H adsorption is increased while the ability of H2 dissociation is reduced.This study provides the theoretical clue for experimental preparation to modify the interaction of metal and support through addition a second metal,further to tune the catalyst performance.%采用密度泛函理论,在电子水平上研究了NiMn双金属与MgO载体间的相互作用以及这种相互作用对H原子吸附和H2解离的影响,并把所得结果与Ni/MgO上相应的结果作比较.研究过程中分别采用完美的和有缺陷的MgO载体负载Ni2Mn2簇,构建了两种催化剂模型.结果表明,表面有缺陷的MgO与活性组分Ni2Mn2间的相互作用大于完美面MgO与活性组分间的相互作用,H原子在有缺陷的MgO负载的Ni2Mn2催化剂上的吸附能大于完美面MgO负载的Ni2Mn2催化剂上的吸附能,并且有缺陷的MgO负载的Ni2Mn2催化剂更有利于H2解离;与Ni4负载的MgO上金属与载体间相互作用相比较,添加第二种金属Mn会使活性组分与MgO载体间的相互作用减弱,吸附H原子的能力增强,但是不利于H2解离.此结果为通过加入第二种金属或改变载体来调变金属-载体间相互作用进而改变催化剂性能的实验研究提供了理论线索.