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Unknown monoclinic NO[Ni(NO3)3] and triclinic modifications of NO[M(NO3)3] (M: Ni, Co) are obtained from mixtures of N2O5, N2O4, HNO3, and Ni(NO3)2 or Co powder at 40 °C and 70 °C, resp. [ABSTRACT FROM AUTHOR]

The thermal carburization of MoO 3 nanobelts (nb) and SiO 2 -supported MoO 3 nanosheets under a 1 : 4 mixture of CH 4  : H 2 yields Mo 2 C-nb and Mo 2 C/SiO 2 . Following this process by in situ Mo K-edge X-ray absorption spectroscopy (XAS) reveals different carburization pathways for unsupported and supported MoO 3 . In particular, the carburization of α-MoO 3 -nb proceeds via MoO 2 , and that of MoO 3 /SiO 2 via the formation of highly dispersed MoO x species. Both Mo 2 C-nb and Mo 2 C/SiO 2 catalyze the dry reforming of methane (DRM, 800 °C, 8 bar) but their catalytic stability differs. Mo 2 C-nb shows a stable performance when using a CH 4 -rich feed (CH 4  : CO 2 = 4 : 2), however deactivation due to the formation of MoO 2 occurs for higher CO 2 concentrations (CH 4  : CO 2 = 4 : 3). In contrast, Mo 2 C/SiO 2 is notably more stable than Mo 2 C-nb under the CH 4  : CO 2 = 4 : 3 feed. The influence of the morphology of Mo 2 C and its dispersion on silica on the structural evolution of the catalysts under DRM is further studied by in situ Mo K-edge XAS. It is found that Mo 2 C/SiO 2 features a higher resistance to oxidation under DRM than the highly crystalline unsupported Mo 2 C-nb and this correlates with an improved catalytic stability. Lastly, the oxidation of Mo in both Mo 2 C-nb and Mo 2 C/SiO 2 under DRM conditions in the in situ XAS experiments leads to an increased activity of the competing reverse water gas shift reaction., Competing Interests: The authors declare that there is no conflict of interest regarding the publication of this article., (This journal is © The Royal Society of Chemistry.)

Molybdenum carbide (β-Mo 2 C) supported on carbon spheres was prepared via a carbothermal hydrogen reduction (CHR) method from delaminated nanosheets of molybdenum(vi) oxide (d-MoO 3 /C). The carburization process was followed by combined in situ XANES/XRD analysis revealing the formation of molybdenum oxycarbide Mo 2 C x O y as an intermediate phase during the transformation of d-MoO 3 /C to β-Mo 2 C/C. It was found that Mo 2 C x O y could not be completely carburized to β-Mo 2 C under a He atmosphere at 750 °C, instead a reduction in H 2 is required. The β-Mo 2 C/C obtained showed activity and stability for the dry reforming of methane at 800 °C and 8 bar. In situ XANES/XRD evaluation of the catalyst under DRM reaction conditions combined with high resolution TEM analysis revealed the evolution of β-Mo 2 C/C to Mo 2 C x O y /C. Notably, the gradual oxidation of β-Mo 2 C/C to Mo 2 C x O y /C correlates directly with the increased activity of the competing reverse water gas shift reaction.