Study on the mechanism of methane activation on Co-based catalysts with variable valence

Abstract

Methane is an important hydrocarbon gas that plays a key role in energy production and utilization. In this study, the mechanism of methane activation on Co (1 0 0), CoO (1 0 0), and Co₃O₄ (1 1 0) surfaces is thoroughly analyzed using density functional theory, revealing the performance differences in methane activation due to different valence states of cobalt. On the Co (1 0 0) surface, methane dehydrogenation mainly proceeds through direct dehydrogenation and O-assisted dehydrogenation, with the O-assisted dehydrogenation having a higher energy barrier. The energy barrier on the CoO (1 0 0) surface is significantly higher than that on the Co (1 0 0) surface, thus it is not favorable for methane activation. In contrast, the energy barrier for methane dissociation and dehydrogenation on Co₃O₄ (1 1 0) is the lowest, with Co³⁺ exhibiting the best catalytic performance. Additionally, the activation effect of Co²⁺ sites on methane is similar to that on the CoO (1 0 0) surface, and is less effective than Co⁰ and Co³⁺, indicating that the Co²⁺ and Co³⁺ on the Co₃O₄ (1 1 0) surface do not show a significant synergistic effect in catalytic reactions. These research findings help to reveal the mechanistic role of different cobalt valence states in methane activation at the atomic level, providing important guidance for the design of efficient methane catalytic conversion catalysts.