Ab-initio Insight Into Unravel The Active Sites And Mechanisms For C-S Bond Activation In Alumina-supported Pt Catalysts

How to reduce the sulfur content in diesel products effeciently has become the key to produce ultra sulfur clean fuels.Supported noble metal catalysts have higher desulfurization activity compared with the traditional Mo based sulfide catalysts.In recent years,related studies have shown that the interface site can also be the active sites of catalyticreaction.Therefore understanding the active sites of metal/oxide catalysts is of great significance in heterogeneous catalysis.In this work,we performed periodic density functional theory calculations to study the C-S bond activation of CH₃SH on Pt/?-Al₂O₃ catalysts.First principle periodic DFT calculations have been used to study the C-S bond activation of CH₃SH on Pt/?-Al₂O₃ catalysts.Five different types of sites were investigated,which are single Pt atom site in Pt₁/?-Al₂O₃,Pt?111?site in Pt slab/?-Al₂O₃,and top-edge,interface,atop-Al sites in Pt nanorod/?-Al₂O₃ respectively.By the analysis of Methanthiol C-S bond activation,interface site have the lowest barrier?1.07 eV?and the maximum reaction energy?-1.05 eV?.On the basis of energetic analysis,we propose that the interfacial Pt?type I?site,summarized as the“Pt-Al”dual perimeter site,could be the active site for the C-S bond activation.Thiophene tends to adsorb at the bridge-hollow site of Pt nanorod.The adsorption energy of thiophene at the top layer seems to be the largest?-3.05 eV,-3.07 eV?.By analyzing the energy barrier and reaction energy of thiophene C-S bond activation,it is found that thiophene prefer breaking C-S bond at the topedge site and interface site.The presence of alumina support adversely impact catalytic performance of Pt nanoparticle itself,but exert positive influence along Pt/alumina interfacial boundary.The origin of this positive effect on the C-S bond activation over the“Pt-Al”dual perimeter site can be understood from the electronic perspective,in which the active interfacial Pt atoms act as electron acceptors(Pt^?-)while alumina support acts as electron donors.The electron-rich property of Pt^?-and the energy-level downshifting of the C-S anti-bonding orbitals of CH₃SH both facilitate the electronic transition from Pt to the C-S anti-bonding orbitals,leading to subsequent C-S bond cleavage.The charge transferred from support to Pt is the determining factor to activate the C-S bond of CH₃SH and is dependant on the temination type of alumina and particle size of Pt.The present work provides geometric and electronic insights into the nature of active sites and shed light on the design of more active metal/oxide catalysts toward catalytic desulfurization.