A novel approach to the synthesis of bulk and supported β-Mo2C using dimethyl ether as a carbon source

Abstract

In view of the fact that H₂ was necessarily added into gas-state carbon sources in order to remove the surface carbon barrier for the complete carburization of Mo oxides to form Mo carbides, in this paper we proposed a simple synthetic route to overcome this issue. The current approach used a new carbon source, dimethyl ether (DME), as feed gas without H₂ addition and employed a pre-heating (PH) method before introducing DME into the reactor. With this novel approach we successfully prepared bulk and CNT supported molybdenum carbides. Note that the removal of carbon deposit by H₂ from DME thermal decomposition and PH-induced surface reconstruction can promote the carburization process. The formation mechanism of Mo carbides was proposed using X-ray diffraction (XRD) and rapid heating reaction mass spectrometry (RH-MS) characterizations. The complete synthesis process involved reduction–carburization of Mo precursors by DME and their thermal decomposition product CH₄, via the pathway of MoO₃/Mo₄O₁₁ → MoO₂ → MoO_xC_y/MoC_1−x → β-Mo₂C. The composition of gas-phase products was predominantly H₂, CO and CH₄ with a very small amount of CO₂ and (or almost no) H₂O.