Recently, the Theoretical Catalysis Research Group of the State Key Laboratory of Catalysis Basics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences and researchers from the University of St Andrews in the UK have made progress in the study of the interaction between carbon and transition metals. The relevant results were published in the latest issue of "Nano Express Letter (Nano Letter, 2011, 11 (2), pp 424–430, DOI: 10.1021 / nl103053t).
In-depth study of the interaction between carbon and transition metal catalysts is of great significance for understanding the formation of carbon deposits during catalytic reactions such as synthesis gas conversion, alkane activation, and water gas changes, suppressing catalyst deactivation, and improving catalyst stability. At the same time, this study is of great reference value for understanding the growth mechanism of graphene on metal surfaces. As a new type of two-dimensional carbon material, graphene has very important application prospects in the fields of high-performance nanoelectronic devices, composite materials, field emission, gas sensors, and energy storage.
Researcher Li Weixue and his doctoral student Xiufang Ma combined with the R. Schaub research group of the University of St Andrews in the UK using density functional theory calculations and tunnel scanning electron microscopy experiments. Through the adsorption of ethylene on the surface of Rh (111) and the temperature-programmed cracking, they conducted in-depth research. Nucleation process and growth mechanism of graphene on Rh (111) surface. Theoretical calculation results show that the difficulty of nucleation and the size of its precursors are determined by the relative strength of carbon-carbon bonding and the competition between carbon and metal bonding. On this basis, through the cooperation of theory and experiment, the researchers accurately determined that the precursor of graphene nucleation on the surface of Rh (111) is composed of clusters of seven six rings and a total of 24 carbon atoms; After the nucleation precursor is formed, the carbon clusters further grow into complete graphene through the SmoluchowskiRipening mechanism.
Since the strength of the interaction between carbon and metal will vary with the metal catalyst and surface orientation, the results of this study mean that the difficulty of carbon nucleation on the surface area of ​​the catalyst can be affected by changing the composition and structure of the catalyst. Controlling the size of the precursor helps to improve the ability of the catalyst to resist carbon deposition and suppress deactivation.
The research results also have some enlightenment value on how to further improve the large-scale preparation of high-quality graphene.
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