CO分子在不同类型Al2O3表面的吸附构型和电子结构

采用基于赝势平面波基组的密度泛函理论方法对CO分子在α-Al₂O₃（0001）以及γ-Al₂O₃的（100）、（110C）、（110D）表面上的吸附构型和电子结构进行系统研究.计算结果表明,CO倾向于选取C端吸附在表层Al原子上,并主要通过其5σ轨道与表面发生作用,吸附后部分电子从CO转移到底物,导致各Al₂O₃表面功函均发生不同程度的下降,与气相相比,吸附后CO分子的C-O伸缩振动频率均发生蓝移.通过对比CO在各表面上的吸附情况,可以看出CO可作为检测Al₂O₂不同类型表面活性中心的有效探针分子.

Geometry and Electronic Structure of the Adsorption of CO Molecules on Different Al2O3 Surfaces

Periodic density functional theory calculations using pseudopotential plane-waves were performed systematically to investigate the surface relaxation of different Al₂O₃ surfaces includingα-Al₂O₃ （0001） andγ-Al₂O₃（110）,（110C）,and（110D） surfaces,as well as the adsorption of CO molecules on these surfaces.Our calculated results indicate that the CO molecules tend to adsorb perpendicularly on the Al atoms at the surface through carbon atoms and interactions were observed between the CO 5σstate and the substrate.After adsorption,some electrons transferred from the CO molecules to the surface and accordingly the surface work functions of the different Al₂O₃ surfaces decreased.The adsorption results in small perturbations of the C-O bond length and the corresponding C-O stretching frequency was blue-shifted in all the adsorption structures.By examining the results of the CO adsorption on the different surfaces,it is clear that CO can be used as an effective probe molecule to distinguish the active adsorption sites on the different Al₂O₃ surfaces.