A Theoretical Study Of Xenon And Krypton Adsorption On Graphene Decorated With Transition Metal

Both Xenon and Krypton are playing important roles in the industry, medical, lifeand research and their preparation is mainly from the air liquefaction separation.However, their properties are so similar that it’s hard to separate them, which impedestheirs further application. How to separate them effectively has been a big question.Solvent absorption by solid is the most common method to do so. If we can find out theessence of the Xenon’s and Krypton’s adsorption on the solid surface, we will achieveremarkable results when choosing the adsorption substrate. By far, the researches ofgas-solid week interaction in experiments are mainly from the perspective of scatteringand spectroscopy. But there are some difficulties and limitations during the operation.Theoretical calculation provides a new method and idea to reveal the nature ofinteraction between Xe, Kr and solid surface.The adsorptions of Xe, Kr on solid surfaces are such ideal model to study weakinteraction that they are extensively investigated all the time. However, almost all thesubstrates are metal or metallic oxide surface. Graphene, which has unique structure andexcellent properties, has attracted the attention of researchers both from home andaboard. In recent years, researches mainly focus on the decorating and doping ofgraphene with transition metals. And it has been proved that graphene decorated withtransition metal has higher gas sensitivity and catalytic activity. However, theadsorptions of rare-gas atoms on the metal-decorated graphene surface have not beeninvestigated. Therefore, in the present work, we aim to understand the rare-gas atoms’,including Kr and Xe, adsorption behavior on Pd-and Pt-decorated graphene. Thecalculation is carried out by MP2and M06-2x methods. The results of this study areshown as follows:(1)The adsorption of Xe, Kr on the graphene is physisorption. The order of theadsorption energy of the three site is Hollow> Bridge> Top. The greater the adsorptionenergy the smaller the equilibrium distance, mostly as a rule. The interaction betweenXe and graphene is stronger than that between Kr and graphene. The results atMP2/AVTZ level is in excellent agreement with the previous experimental andtheoretical study.(2)Xe and Kr preferentially adsorb at the bridge site of the metal-decoratedgraphene and the energy of top site is very similar with that of bridge site. Theinteraction between Xe, Kr and metal-decorated graphene is much higher than thatbetween Xe, Kr and pure graphene or metal surface. Besides, the decorating of metalhas enlarged the difference between the adsorption energy of Xe on graphene and that of Kr on graphene. It is clear that the metal-decorated graphene has much higher Xe, Krsensitivity and selectivity.(3)The NEDA is carried out at M06-2x/ARD level. It shows that the Polarizationplays the most important role in the adsorption. In addition, the charge transfer energydoes a very large contribution to the total energy when Xe, Kr adsorbed on the bridgesite of the metal-decorated graphene.