A Density Functional Theory and Microkinetic Study of Acetylene Partial Oxidation on the Perfect and Defective Cu₂O (111) Surface Models

Abstract

The catalytic removal of C2H2 by Cu2O was studied by investigating the adsorption and partial oxidation mechanism of C2H2 on both perfect (stoichiometric) and CuCUS-defective Cu2O (111) surface models using density functional theory calculations. The chemisorption of C2H2 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 C2H2 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 C2H2 by a series of radicals including H, OH, HO2, CH3, O, and O2 following the Langmuir–Hinshelwood mechanism have been compared. On the perfect Cu2O (111) surface model, the activity order of the adsorbed radicals toward H-abstraction of C2H2 is: OH > O2 > HO2 > O > CH3 > H, while on the defective Cu2O (111) surface model, the activity follows the sequence: O > OH > O2 > HO2 > H > CH3. The CuCUS defect could remarkably facilitate the H-abstraction of C2H2 by O2. The partial oxidation of C2H2 on the Cu2O (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 C2H2 H-abstraction by O2 dictates the C2H2 overall reaction rate on the perfect Cu2O (111) surface model and the chemisorption of C2H2 is the rate-determining step on the defective Cu2O (111) surface model. The results of this work could benefit the understanding of the C2H2 reaction on the Cu2O (111) surface and future heterogeneous modeling.

Keywords

• acetylene
• partial oxidation
• density functional theory calculations
• Cu₂O (111) surface
• defects