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Breakthrough in the synthesis of methanol from carbon dioxide via hydrogenation Author/Source: Sinochem News Network Date: 2021-06-09 Clicks: 4 Recently, the research team led by Professor Liu Changjun from the School of Chemical Engineering at Tianjin University used density functional theory to study the feasibility of using indium oxide-supported silver catalysts for the hydrogenation of carbon dioxide to produce methanol. They established the theoretical pathways for this reaction and verified those predictions through experiments, achieving a breakthrough in the development of highly active and selective catalysts for the hydrogenation of carbon dioxide to methanol. In the context of carbon neutrality, how to efficiently convert carbon dioxide has become a focus of interest for chemists. Among the various possible chemical reactions, the one with the greatest potential for large-scale application is the reaction of carbon dioxide hydrogenation to produce methanol. Currently, carbon dioxide hydrogenation catalysts with high activity and high selectivity have become key to further applications. Silver catalysts have been used to study the photocatalytic and electrochemical reduction of carbon dioxide. However, no studies have yet confirmed its high activity for the selective hydrogenation of carbon dioxide to methanol. Liu Changjun explained that since 2013, they and their collaborators have confirmed through theoretical calculations and experiments that indium oxide containing oxygen vacancies, along with metal catalysts such as palladium, platinum, gold, nickel, rhodium, and iridium loaded on it, exhibit high methanol selectivity and high activity in the hydrogenation of carbon dioxide to produce methanol; moreover, these metal catalysts loaded on indium oxide also show good stability. There are no reports yet on the use of indium oxide-supported silver catalysts in the heterogeneous hydrogenation of carbon dioxide to methanol. In this latest study, Liu Changjun’s research team focused on metal silver catalysts as partners for indium oxide, and by adjusting the combination of silver and indium oxide, they turned the Ag/In₂O₃ catalyst into a highly active catalyst for the hydrogenation of carbon dioxide to produce methanol. The researchers first analyzed the interaction between silver and the surface of indium oxide containing oxygen vacancies through density functional theory calculations. The calculation results show that the interfacial sites between the two can effectively activate carbon dioxide molecules, making it easier for them to undergo hydrogenation reactions at these sites. Based on the results of theoretical calculations, the researchers prepared Ag/In₂O₃ catalysts using the deposition-precipitation method, and evaluated their reaction activity in comparison with indium oxide catalysts. The comparison results show that the addition of silver improved the ability to produce methanol via carbon dioxide hydrogenation, significantly reducing the apparent activation energy for its conversion. The results of the stability tests also show that the Ag/In₂O₃ catalyst possesses better catalytic stability; after 10 hours of reaction, its activity retention rate was 90.5%, compared to 80.4% for the In₂O₃ catalyst. Furthermore, characterization experiments also confirmed that the addition of silver promotes the formation of surface oxygen vacancies, thereby increasing the number of such vacancy sites and facilitating the adsorption and dissociation of carbon dioxide. The researchers say they hope this work will provide guidance for the rational design of highly selective indium-based catalysts.