Identifying active sites of Co3O4 catalysts for C2H2 oxidation using combined computational and experimental methods

Abstract

Combined computational and experimental studies are carried out to unravel the role of active centers on C₂H₂ oxidation over Co₃O₄ catalysts. Density functional theory (DFT) studies indicate that Co²⁺ ions on Co₃O₄ (110)-A exhibit stronger reducibility than Co³⁺ and oxygen species activated by Co²⁺ have better catalytic performance. On the Co₃O₄ (110)-B surface, Co²⁺ ions represent the presence of oxygen vacancies. O₂ can be adsorbed on oxygen vacancies to form active O²⁻ species, which oxidize C₂H₂ to CO₂ and H₂O. Co₃O₄ catalysts with different Co²⁺ contents are prepared to experimentally verify calculation results. The catalytic activity varies in the order of Co₃O₄-sheets-reduced > Co₃O₄-sheets > Co₃O₄-sticks-reduced > Co₃O₄-sticks, in accordance with the trend of Co²⁺ contents. Furthermore, microkinetic studies prove that the key factor of C₂H₂ oxidation is C–C dissociation. Decreasing the C–C cleavage barrier significantly enhances the overall reaction rates. Both computational and experimental results show that the presence of Co²⁺ on the surface of the Co₃O₄ catalyst is the main contributing factor to the activity of C₂H₂ oxidation. As minimal research has been reported on C₂H₂ oxidation, this study may provide a guideline for eliminating other volatile organic compounds over Co₃O₄ catalysts.