论文部分内容阅读
本文应用原子交迭和电子离域-分子轨道(ASED-MO)理论,研究了CO在Ni(100)表面活化及硫中毒机理。计算结果表明,CO顶位吸附比四度中心位吸附有更大的结合能。当CO分子被吸附于顶位时,其2π反键轨道将获得0.72个电子,解离能将从自由CO分子的11.1eV降到2.15eV。当吸附于四度中心位时,2π轨道将获得1.22个电子,解离能进一步降到1.85eV。由此看来,吸附于四度中心位的CO分子将具有更大的活性。当Ni(100)面上同时存在S原子吸附时,不同相对位置CO吸附结合能的计算结果表明,一个吸附S原子将“堵塞”四个最近邻顶位和四个最近邻中心位对CO的吸附作用,而对更远一些的吸附位则没有什么影响。这些结果支持了被吸附S原子对CO吸附的影响主要是近程性“结构效应”的观点。被吸附S原子的上述“堵塞”作用,吸附S原子后CO激活吸附位的减少,及可能存在的其它因素,构成了Ni表面的硫中毒。
In this paper, atomic activation and electron delocalization-molecular orbital (ASED-MO) theory are used to study the mechanism of CO activation on Ni (100) surface and sulfur poisoning. The calculated results show that the top adsorption of CO has greater binding energy than the fourth-degree center. When the CO molecule is adsorbed at the top position, the 2π antibonding orbital will get 0.72 electrons and the dissociation energy will drop from 11.1eV of the free CO molecule to 2.15eV. When adsorbed at the center of the fourth degree, the 2π orbit will acquire 1.22 electrons and the dissociation energy further drops to 1.85eV. Seen in this light, CO molecules adsorbed to the center of the fourth degree will have greater activity. When S atoms are adsorbed on Ni (100) surface simultaneously, the CO binding energy at different relative positions shows that one adsorbed S atom will “block” the four nearest neighbors and the four nearest neighbors to CO Adsorption, while the farther adsorption sites have no effect. These results support the view that the effect of adsorbed S atoms on CO adsorption is mainly a “structural effect” of proximity. The “plugging” effect of adsorbed S atoms, the reduction of CO-activated adsorption sites after the adsorption of S atoms, and possibly other factors, constitute sulfur poisoning on the Ni surface.