γ-Mo2N catalysts exhibit excellent activity and stability in ammonia decomposition reactions. However, the influence of oxygen on its activity is still unknown. In this work, two γ-Mo2N catalysts with different oxygen content are synthesized using temperature-programmed nitridation of α-MoO3. The γ-Mo2N catalysts are highly oxidized and their ammonia decomposition performance is closely related to their oxygen content. The activity of γ-Mo2N with high oxygen content (HO-γ-Mo2N) is much higher, whose H2 formation rate at 550°C is 3.3 times higher than the γ-Mo2N with low oxygen content (LO-γ-Mo2N). This is mainly attributed to two aspects: on the one hand, the higher valence state of Mo in the HO-γ-Mo2N leads to stronger Mo─NH3 bonds, which promotes the adsorption and activation of NH3. On the other hand, the H generated by N─H bond breaking is more easily migrated to O, which avoids excessive H occupying the γ-Mo2N active sites and alleviates the negative effect of hydrogen poisoning.
Read full abstract