First-Principles Theoretical Study On Dry Reforming Of Methane Over Perfect And Boron-Vacancy-Containing H-Bn Sheet-Supported Ni Catalysts

The entire reaction mechanism of the dry reforming of methane (DRM) as well as the competition processes over perfect and boron-vacancy-containing h-BN sheet-supported Ni-catalysts (labeled Ni-2/h-BN and Ni-2/h-BN-B-D) was studied by density functional theory calculations in the present work. Our calculation results show that B-defected h-BN strongly binds to the Ni-2 active sites (i.e., shows a strong metal-support interaction (SMSI) character) due to the better electron transfer between Ni-2 sites and the support. It was found that CH4 is easier to activate than molecular CO2. The activation of CO2 occurs on the surface of Ni-2/h-BN through a direct route, whereas it is prone to follow a hydrogen-assisted path for Ni-2/h-BN-B-D via the COOH* intermediate, and the results show that the oxidant O* is easily formed on the surface of Ni-2/h-BN-B-D. It was also found that O* is the main oxidant agent for CHx* intermediates through the CH3-O oxidation mechanism. The reaction kinetic analysis indicated that the reverse water gas shift reaction (RWGS) is much more favorable than DRM (1.30 vs. 1.72 eV) over the Ni-2/h-BN system, whereas the RWGS and DRM are comparable on Ni-2/h-BN-B-D (1.77 vs. 1.66 eV), suggesting a high DRM activity on Ni-2/h-BN-B-D. Moreover, neither methane cracking nor a Boudouard reaction to form C* species is thermodynamically and kinetically unfavorable over Ni-2/h-BN-B-D; hence, Ni-2/h-BN-B-D has strong resistance to carbon deposition. Compared to Ni(111), both Ni-2/h-BN-B-D and Ni-2/h-BN show strong resistance to carbon deposition. Our results provide a further mechanistic understanding of the DRM over an Ni-based catalyst through the SMSI characteristic and the SMSI favors strong resistance to carbon deposition.