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本文用SCC-DV-X_a方法研究了Co与K在Ni(100)面上共吸附时,K对CO助催作用机理。计算表明,Ni(100)面上区域电荷密度的提高对CO活性没有较大的影响,K对CO助催作用主要表现在K~(δ+)对CO的静电作用,并由此导致K→Ni→CO的电荷传递。使CO 2π电子占据数上升,CO活性提高。K与CO之间没有强的化学成键作用。在Ni(100)表面存在CO~(δ-)…K~(δ+)离子络合对。CO在Ni(100)面上吸附时,5σ电子与Ni表面σ电子发生排斥,其电子云由C向O移动。而4σ、1π的电子云则由O向C移,结果在Ni-CO键中,4σ的成键作用较5σ强。CO 5σ中C原子的杂化形式也由sp杂化转化为sp~2杂化。K的共吸附使CO各轨道的电离势有所上升。
In this paper, using SCC-DV-X_a method to study the co-promoting mechanism of K on CO when Co and K are co-adsorbed on Ni (100) surface. Calculations show that the increase of the charge density on the Ni (100) surface has no significant effect on the CO activity. The promoting effect of K on CO is mainly reflected by the electrostatic effect of K ~ (δ +) on CO, which leads to the increase of K → Ni → CO charge transfer. So that the CO 2 π electronic occupancy increased, CO activity increased. There is no strong chemical bonding between K and CO. CO ~ (δ-) ... K ~ (δ +) ion complexation exists on Ni (100) surface. When CO is adsorbed on the Ni (100) surface, 5σ electrons and the σ surface on the Ni surface repel each other, and the electron cloud moves from C to O. However, the electron cloud of 4σ and 1π shifts from O to C, and as a result, in the Ni-CO bond, the bonding effect of 4σ is stronger than that of 5σ. The hybrid form of C atom in CO 5σ is also transformed from sp hybrid to sp ~ 2 hybrid. The co-adsorption of K increases the ionization potential of CO orbits.