The catalytic mechanism of carbon dioxide hydrogenation to methanol was revealed

The use of renewable energy such as solar energy, hydrogen production from hydrogen production coupled with carbon dioxide hydrogenation to methanol through photocatalysis, photocatalysis or electrocatalysis, is an effective strategy to achieve the goal of carbon neutrality, and it is also one of the important paths of artificial photosynthesis. Recently, the team of academician Li Can and researcher Feng Zhaochi of Dalian Institute of Chemical Physics, Chinese Academy of Sciences has made new progress in the research on the mechanism of carbon dioxide hydrogenation to methanol. Using operando IR-MS technology, the team revealed the synergistic promotion mechanism of adjacent Zn-O-Zr asymmetric active centers for carbon dioxide activation and catalytic hydrogenation on ZnZrOx solid solution catalysts. The results were published in the Journal of the American Chemical Society.

Schematic diagram of the catalytic mechanism of carbon dioxide hydrogenation to methanol. Photo courtesy of Dalian Chemical Properties

At present, the selective regulation of the product and the stability of the catalyst in the process of CO2 hydrogenation to methanol are the key factors restricting the efficient preparation of methanol. In response to this problem, Li Can’s team developed a series of bimetallic oxide solid solution catalysts in the early stage. Among them, ZnZrOx catalyst is the representative, which can achieve high selectivity and high stability of methanol synthesis at the same time. Moreover, the modification and doping of the catalyst can further improve the catalytic performance of the reaction. At present, solid solution catalysts have been widely used by researchers at home and abroad to convert carbon dioxide to methanol and other carbon dioxide hydrogenation conversion reactions. Nevertheless, the adsorption activation of hydrogen and carbon dioxide on the surface of solid solution catalysts and the microscopic mechanism of how hydrogen and carbon dioxide can be hydrogenated into methanol are still not clear. 

In this work, operando technology and theoretical calculation methods are used to track surface reaction processes and catalyst performance. The results showed that the asymmetric active center of Zn-O-Zr on the ZnZrOx catalyst played an active role in activating and promoting the formation and transformation of carbonate and formate intermediate species. At the beginning of the reaction, carbon dioxide is mainly adsorbed on the surface by carbonate species in the double-tooth configuration, and hydrogen is activated in the form of heterocleavage dissociation, which is easy to form C-H bonds, and methanol is produced by coupling proton transfer with equal molar amounts.

During the whole reaction, the Zn-O-Zr asymmetric sites on the surface of the catalyst exhibited a synergistic effect at the atomic level, so it was found that the asymmetric active centers of such adjacent heterogenes were found to be the essential reason for catalyzing the high-performance synthesis of methanol. (Source: Sun Danning, China Science News)

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