Double-Site Doping of a V Promoter on Ni_x-V-MgAl Catalysts for the DRM Reaction: Simultaneous Effect on CH₄ and CO₂ Activation

A series of V-dopAed layered double hydroxide-derived Ni-x-V-MgAl catalysts were prepared and applied in the dry reforming of methane (DRM) reaction. The catalyst activity was enhanced with increasing amounts of a V promoter and was optimal at Ni/V = 10. Various characterizations showed that an appropriate amount of the V additive was doped in both the Ni sites and the MgAl mixed-oxide support. The addition of the V promoter not only improved the dispersion of Ni sites but also increased their electron cloud density. The activation energy of CH4 cracking to form CH3 and H species decreased from 72.1 kJ.mol(-1) on pure Ni(111) to 37.1 kJ.mol(-1) on V0.50Ni(111). Meanwhile, the adsorption and activation abilities of CO2 were affected by the insertion of V species in the MgAl mixed-oxide support. In situ CO2 infrared spectrometry verified that the addition of the V promoter inhibited the formation of nonactivated multidentate carbonate and significantly increased the content of the monodentate carbonate species, which was considered as the intermediate of CO2 activation. Thus, the enhanced CO2 activation ability of the Ni-10-V-MgAl catalyst suppressed the generation of carbon deposits during the DRM reaction, thereby achieving excellent stability in long-term testing compared to undoped Ni-MgAl.