Researchers reveal structural evolution during molybdenum carbide formation at atomic level

1–x In situ studies on structural evolutions during the simple synthesis of catalysts. Credits: Yu Jiafeng” width=”650″ height=”393″/>

In situ investigations on structural evolutions during simple synthesis of cubic α-MoC1–x catalysts. Credit: Yu Jiafeng

Transition metal carbides have received great attention due to their unique catalytic properties similar to precious metals. Among them, α phase molybdenum carbides (α-MoC1-x) shows high activity in the activation of water at an ultra-low temperature in the water-gas transition and the aqueous phase reforming of the methanol reaction.

However, the cubic α-MoC preparation process1-x often with high energy consumption requires an extra ammonification process or substantial precious metal aid which severely limits its application.

Recently, Professor of the Chinese Academy of Sciences (CAS) Dalian Institute of Chemical Physics (DICP). SunJian, Dr. Yu Jiafeng and Dr. A joint research team led by Liu Yuefeng, Professor of the Chinese Academy of Sciences. Germany Karlsruhe Institute of Technology (KIT) observed the dynamic evolution of the crystal structure at the atomic level, confirming that it is cubic MoO.x phase was the key intermediate for synthesis of face-centered cubic α-MoC1-x with a one-step carburizing process.

This work has been published Journal of the American Chemical Society on November 23.

The researchers performed qualitative and quantitative analyzes of the crystalline phases formed as intermediates during the carburization process, and also followed the evolution of morphology and crystal structure by environmental transmission electron microscopy.

They found MoO3 first to the cubic oxygen-deficient Mo oxide (MoOx) at a low temperature (300°C) due to H activation2 with traces of Rh. Next, carbon atoms can occupy oxygen vacancies to form cubic MoO.xCy Intermediate products required for further conversion to α-MoC1–x over the topological path. The final stage of carbides was dependent on the primary structure and structural evolution path of the first intermediates during the carburization process, where a slow and gradual reduction is required for active α-MoC formation.1–x.

prof. “This study reveals the key factor of structural evolution during the carburizing process,” Sun said. “It provides an easier and universal strategy for the one-step synthesis of α-MoC.1–x

More information:
Xingtao Sun et al., In situ Investigations on Structural Evolutions During Easy Synthesis of Cubic α-MoC1–x catalysts, Journal of the American Chemical Society (2022). DOI: 10.1021/jacs.2c08979

Provided by the Chinese Academy of Sciences

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