Preparation and process investigation of molybdenum carbide and their N-doped analogue by calcination

The crystal structure of Mo2C can be derived from close packed Mo atoms with partial occupation of C atoms in the octahedral interstices. Mo2C and MoC were successfully synthesized by calcinaiton of the lab-made precursor containing 1,8-diaminonaphthalene and ammonium molybdate at carbon/molybdenum ratio of 2.0, 2.25, 2.7 and 4.5, respectively. High temperature XRD was used in the formation process study of Mo2C, which presents MoO2 as an important intermediate in formation of Mo2C. A reduction of the carbon/molybdenum ratio to 1.8 in the precursor caused shifts of XRD reflections in Mo2C-0.4. Rietveld refinement of the XRD reflections of Mo2C-0.4 reveals a partial nitrogen substitution of carbon atoms in Mo2C, which is confirmed by the theoretical calculation. The theoretical carbon and nitrogen contents of Mo2N0.6C0.4 agree with the experimental carbon and nitrogen content results of Mo2C-0.4 from element analysis. This confirms the substitution of carbon by nitrogen in the Mo2C lattice.