Syngas to ethanol on MoCu(211)surface:Effect of promoter Mo on C-O bond breaking and C-C bond formation

摘要

The mechanism of syngas to ethanol on MoCu(211)surface has been researched by density functional theory(DFT)calculation,and the effects of Mo as a promoter on C-O bond breaking and C-C bond formation have been discussed.Calculations show that Cu-Mo atoms constitute the active sites on MoCu(211)surface after Mo atom being served as a promoter of Cu catalyst.Compared with Cu(211),MoCu(211)has two improvements.Firstly,CH_(3) is the most advantageous monomer on the MoCu(211)surface,which provides abundant CH_(3) intermediate for syngas to ethanol.Secondly,the C-C bond is formed mainly by inserting CHO into the abundant CH_(3),and the generated CH_(3)CHO through multiple steps of hydrogenation to generate C_(2)H_(5)OH.The key of the promoter Mo on the MoCu(211)surface also has been verified by the analysis of its electronic properties.Differential charge density shows that the massive electron transfer from Mo to Cu,projected density of states(pDOS)shows that the electron transfer from Mo to Cu makes the d-band center of MoCu(211)nearer to the Fermi level,these indicate that the MoCu(211)catalytic capacity increased.The addition of Mo in the Cu-based catalyst not only can effectively solve the problem of C-O bond breaking,but also promote C-C bond formation.About the influence of Mo content on C-O bond breaking and C-C bond formation,compared with MoCu(211),the DFT results and the d-band center of Mo_(2)Cu(211)show that the increase of Mo content could not promote the synergistic effect of Cu/Mo on the generation of ethanol more effectively.