Insights on active sites of Cu/CeO2 catalyst for CO2 hydrogenation to methanol: A density functional theory study

Abstract

Methanol is well-known as liquid sunshine, and the synthesis of methanol from CO 2 hydrogenation can be an effective path to mitigate the greenhouse effect and convert energy. In this work, the active sites over Cu/CeO 2 catalyst on reaction mechanisms of CO 2 hydrogenation to methanol were studied based on density functional theory calculations. Through the electron density and density of states analysis, the interaction between key intermediates and active sites are elucidated, CO 2 is more easily activated by CeO 2 , whereas the H 2 dissociation occurs on Cu clusters. Meanwhile, the Cu cluster exhibit a significant interaction with the carbon atom in some key intermediates, which makes the Cu cluster the primary sites for hydrogenation of carbonate intermediates. Migration of spilled H to interfacial sites facilitates activation of CO 2 , highlighting the importance of interfacial sites in this process. CO 2 activation to COOH and H-assisted dissociation to CO are the most charge transferring processes, making them more reactive, thus facilitating subsequent reactions towards the reverse water-gas shift (RWGS) reaction and CO-hydrogenation pathways. The dominant pathway for methanol synthesis is CO 2 → COOH→ CO (or CO 2 +H→ CO ​+ ​OH) → COH → HCOH→ H 2 COH → CH 3 OH, and the rate-determining steps are CO ​+ ​H → COH and COH ​+ ​H → HCOH with energy barriers of 1.26 and 1.27 ​eV, respectively. • The synergy of Cu cluster, CeO 2 and interfacial sites facilitate the CO 2 hydrogenation to methanol. • Electron density analysis elucidates the distinct roles of active sites in governing intermediate adsorption and activation. • Hirshfeld charge change can serve as a descriptor distinguishing the strength of catalyst-intermediate interactions. • Elucidation of the reaction mechanism for CO 2 hydrogenation to methanol over Cu/CeO 2 catalyst.

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