Preparation of Mo2C by the temperature-programmed reaction between h-MoO3 and CO

Abstract

In the work, the temperature-programmed reaction (TPR) between hexagonal-shaped h-MoO3 and high-purity CO under different heating rates was investigated in order to prepare Mo2C. Various technologies such as TG-DTA-DTG, XRD, FESEM, FT-IR and Raman spectrum as well as the thermodynamic calculation were adopted to analyze the experimental data. The results showed that the physically adsorbed water on the sample surface, the residual ammonium and coordinated water in the internal structure of h-MoO3 were successively released as the temperature increased, and then α-MoO3 and Mo4O11 were formed when the temperature arrived at around 791 K. Upon further increasing the temperature, the reduction process occurred and MoO2 will be generated. Thereafter, the carburization reaction was taken place and the subsequent reaction pathways were significantly different at lower and higher heating rates: at lower heating rates (8 and 12 K/min), the carburization process of MoO2 to Mo2C followed MoO2→MoO2+Mo2C→Mo2C + Mo→Mo2C; while at higher heating rates (16 and 20 K/min), the reaction pathways followed MoO2→MoO2+Mo2C→MoO2+Mo2C + Mo + MoOxCy→Mo→Mo2C, single-phase metallic Mo can be generated. The work also discovered that the as-prepared Mo2C always kept the same platelet-shaped morphology as that of the newly-formed MoO2; while due to the removal of oxygen and the decrease of molar volume during the transformation process, the as-prepared Mo2C exhibited a rougher and more porous morphological structure.