Structure, Dynamics, and Reactivity of Co3O4 Spinel Interacting with 2-Propanol and Water: Insights from Ab Initio Molecular Dynamics Simulations

Heterogeneous catalysis plays a crucial role in the chemical industry, accounting for approximately 25% of industrial chemical production. Transition metal oxides (TMOs) have gained increasing attention as heterogeneous catalysts due to their abundance and lower cost compared to noble metal catalysts. Moreover, conducting oxidation reactions in the liquid phase instead of the gas phase offers several advantages, including milder reaction conditions and catalyst reusability. However, the transition from the metal/gas interface to the TMO/liquid interface introduces a new level of complexity that is challenging to investigate in detail using conventional experimental techniques. Ab initio Molecular Dynamics (AIMD) simulations have emerged as a powerful tool for studying these complex interfaces and capturing their dynamics at the atomistic level. Therefore, this study utilizes AIMD simulations to investigate the oxidation of 2-propanol at the Co3O4 (001)/H2O interface. The choice of 2-propanol as a model reaction allows for the detailed study of a reaction that is complex enough to yield various products but simple enough to be thoroughly examined.

Quantum-mechanical Density Functional Theory with a Hubbard U value (DFT+U) is employed to describe the electronic structure of the Co3O4 spinel. The interaction between Co3O4 ​​​​​​​(001) and 2-propanol is thoroughly investigated, considering the influence of different parameters such as temperature, hydroxylation, and surface termination on the structure and activity of the interface. The activity of the Co3O(001) surface is then compared with that of the Co3O4 ​​​​​​​(111) and Co3O4 ​​​​​​​(110) surfaces. The partial oxidation of 2-propanol is explored in both the liquid and gas phases. In the liquid phase, the impact of temperature, electrochemical conditions, and surface structure is taken into account. Various stages of 2-propanol oxidation are examined through charge analysis. The favorability of the B-terminated Co3O(001) surface for 2-propanol oxidation is discussed. Additionally, the oxidation process in the gas phase is studied by incorporating a true oxidizing agent, such as oxygen species. Furthermore, the fundamental differences between the partial oxidation of 2-propanol in the liquid and gas phases are elucidated.


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