Recently, researchers from the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences and the Karlsruhe Institute of Technology in Germany used multidimensional characterization methods to reveal the carbonization process and formation mechanism of molybdenum carbide (MoC) catalytic materials. The dynamic evolution process of crystal structure was observed at the atomic scale, confirming that cubic molybdenum oxide (MoOx) is a one-step carbonization synthesis α Key intermediate for phase MoC.



According to China Tungsten Online, molybdenum carbide is an ultra-fine gray black powder with a closely arranged hexagonal lattice structure. Due to its electronic structure and catalytic properties similar to precious metals, good thermal stability, mechanical stability, wear resistance and corrosion resistance, it is widely used in the catalytic field. The main types of catalytic reactions include hydrogenation, isomerization, hydrodesulfurization, hydrodenitrogenation, ammonia synthesis Hydrocarbon conversion and synthesis reactions.



In recent years, although molybdenum carbide catalytic materials have attracted widespread attention due to their unique catalytic properties similar to precious metals, their structural evolution process is still not well understood. According to the different crystal structures, MoC can be divided into hexagonal crystalline phases β Molybdenum carbide and cubic crystalline phase α Molybdenum carbide. Hexagonal phase β Compared to molybdenum carbide, cubic crystalline phase α The preparation process of molybdenum carbide is more demanding, generally requiring high pollution, high energy consumption ammoniation treatment or loading of high content precious metals, which increases the production cost of this catalytic material and limits its application.



In order to gain a deeper understanding of the evolution process of molybdenum carbide structure and reduce production costs, researchers from the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences and other institutions have adopted the flame spraying method (FSP) to prepare metastable oxides.



Research has found that after loading trace amounts of rhodium (Rh) on molybdenum oxide prepared by flame jet method, a phase transition can preferentially occur at low temperatures to produce a cubic molybdenum oxide metastable structure rich in oxygen vacancies. Then, carbon insertion and substitution occur while maintaining the crystal phase unchanged, and finally convert into a highly active cubic phase α Molybdenum carbide catalyst. In this process, the formation of cubic MoOx intermediates is crucial, so that the subsequent carbonization process follows a topological transformation carbonization path.



The research findings have been presented in the form of "In Situ Investments on Structural Evolution during the Facile Synthesis of Cubic α- MoC1 – x Catalysts "was published in the Journal of the American Chemical Society.



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