| In recent years,the composition and structure of Au-base bimetallic nano-catalysts have been widely concerned by researchers.The synergistic effect of metal can directly affect the structure and performance of single metal particle catalyst,thus it can improve the catalytic performance of the bimetallic catalyst.Bimetallic catalysts show excellent catalytic activity and selectivity in catalytic hydrogenation reaction,catalytic cracking reaction and catalytic oxidation reaction.Thus bimetallic catalysts have been widely used in various industrial processes.In this paper,we have performed first-principle density functional theory calculations to investigate how the transition metal?TM=Ni,Co,Fe,Ru,Rh,Pd,Os,Ir or Pt?affects the energetics,the electronic structure and the adsorption of small molecules?O2,CO?on the Au surfaces.The results show that the TM?TM=Fe,Co,Ni,Ru,Rh,Pd,Os,Ir or Pt?can activate Au?111?surfaces,thus remarkably improving the ability of gold surfaces to adsorb oxygen,oxygen and carbon monoxide.At the same time,using the Bader charge,we quantitatively analyzes the charge transfer at TM-Au-monomer,TM-Au-dimer and TM-Au-SNMP surface?figure 3-1?.We found that the electrons were mainly transferred from the transition metal atoms to oxygen and carbon monoxide.The charge transfer made the adsorption of O2 on TM-Au surfaces to form a similar O22-or O2-adsorption species,and its O-O and C-O bond length were obviously elongated,which further illustrates that the O2,O,CO interacts with these Au-base bimetallic surfaces.So the importance of the doping of transition metal atoms to the activation of oxygen molecules and carbon monoxide molecules is further explained.Our calculations showed that on the surfaces of Co-Au-dimer,Ir-Au-dimer,Os-Au-dimer,Ru-Au-dimer and Os-Au–SNMP,the oxygen molecule is unstable,and automatically decomposed to O atoms in the process of geometry optimization.The most stable adsorption sites of O2,O on the surface of Au-base bimetallic nano-catalysts are different,but adsorption of CO in the most stable adsorption sites are top site?figure 5-1 a?.In general,for different TM-Au?TM=Fe,Co,Ni,Ru,Rh,Pd,Os,Ir or Pt?bimetallic nano-catalysts surface structures,which have good adsorption properties for O2 and Co adsorption and the adsorption stability of O2,O and CO is:TM-Au-dimer>TM-Au-monomer>TM-Au-SNMP.For different metals,The orders of adsorption stability for O2,O and CO are different.Based on the calculating results,we believed that Ni,Rh,Pd and Pt are ideal doping elements.Secondly,we found that Ni,Rh,Pt doped Au?111?surface have higher activation performance for both oxygen molecule and carbon monoxide.Both Rh and Pt are expensive metals that are not conducive to control the cost of the catalyst.Ni doping on the surface of Au?111?shows a high catalytic activity,which should be further explored in experiment. |
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