Revealing the dynamic formation mechanism of porous Mo₂C: an in-situ TEM study

Abstract

In-situ transmission electron microscopy (TEM) enables direct observation of the micromorphology and microstructure evolution of catalysts in the chemical atmosphere. Studying the structural evolution during the formation of molybdenum carbide using in-situ TEM is helpful for the preparation of high-performance carbide catalysts. Herein, the formation mechanism of porous Mo₂C from MoO₂ nanoparticles (NPs) was studied by in-situ TEM. The formation of Mo₂C was induced by the defects of MoO₂, and the formed Mo₂C facilitated the carbonization of neighboring MoO₂ NPs. The growth rate of Mo₂C between MoO₂ NPs was slower compared to that within a single MoO₂ NP. In addition, the formation and growth of pores in Mo₂C were also studied; the pores grew radially during the early stages from the nucleation sites and later grew branched and curved. As Mo₂C underwent competitive growth, the pores transitioned from straight to curved. Eventually, during prolonged carbonization at high temperatures, Mo₂C underwent sintering.

Keywords

Mo₂C / porous structure / growth mechanism / in-situ TEM

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