A Density Functional Theory and Microkinetic Study of Acetylene Partial Oxidation on the Perfect and Defective Cu(2)O (111) Surface Models

The catalytic removal of C(2)H(2) by Cu(2)O was studied by investigating the adsorption and partial oxidation mechanism of C(2)H(2) on both perfect (stoichiometric) and Cu(CUS)-defective Cu(2)O (111) surface models using density functional theory calculations. The chemisorption of C(2)H(2) on perfect and defective surface models needs to overcome the energy barrier of 0.70 and 0.81 eV at 0 K. The direct decomposition of C(2)H(2) on both surface models is energy demanding with the energy barrier of 1.92 and 1.62 eV for the perfect and defective surface models, respectively. The H-abstractions of the chemisorbed C(2)H(2) by a series of radicals including H, OH, HO(2), CH(3), O, and O(2) following the Langmuir–Hinshelwood mechanism have been compared. On the perfect Cu(2)O (111) surface model, the activity order of the adsorbed radicals toward H-abstraction of C(2)H(2) is: OH > O(2) > HO(2) > O > CH(3) > H, while on the defective Cu(2)O (111) surface model, the activity follows the sequence: O > OH > O(2) > HO(2) > H > CH(3). The Cu(CUS) defect could remarkably facilitate the H-abstraction of C(2)H(2) by O(2). The partial oxidation of C(2)H(2) on the Cu(2)O (111) surface model tends to proceed with the chemisorption process and the following H-abstraction process rather than the direct decomposition process. The reaction of C(2)H(2) H-abstraction by O(2) dictates the C(2)H(2) overall reaction rate on the perfect Cu(2)O (111) surface model and the chemisorption of C(2)H(2) is the rate-determining step on the defective Cu(2)O (111) surface model. The results of this work could benefit the understanding of the C(2)H(2) reaction on the Cu(2)O (111) surface and future heterogeneous modeling.