(513t) Ni-Based Catalysts with Enhanced Coke Resistance for Dry Reforming of Methane

The discoveries of abundant shale gas reserves offer the possibility of catalytic converting light alkanes from shale gas to hydrogen through dry reforming reactions. However, large-scale implementation of this process has been stalled by lack of stable catalysts owing to the rapid deactivation caused by carbon deposition and sintering. Herein, Ni/CeO₂-nanorod catalysts with high activity and stability are synthesized by a hydrothermal method for dry reforming of methane, providing an effective way to solve the deactivation of Ni-based catalysts. Dry reforming reactions are believed to occur via the direct C-H bond dissociation of CH₄ to form surface carbon intermediates over the active metal followed by the oxidation of carbon intermediates to CO. The enhanced stability of the Ni/CeO₂-nanorod catalysts is attributed to the fact that the oxidation rate of carbon species is comparable to their generation rate, which is evidenced by a series of systematical characterization. Compared with commercial supports, CeO₂ nanorods with stronger lattice oxygen mobility and higher oxygen storage capacity generate more mobile active oxygen species that participate in eliminating the carbon deposition. Moreover, the fraction of Ni species in higher oxidation state, which are less active for direct methane dissociation over Ni/CeO₂-nanorod is increased as a result of the strong metal-support interaction. As a consequence, the balance between the rate of carbon generation (i.e., direct C-H bond dissociation of CH₄) and the rate of carbon consumption (i.e., oxidation of formed carbon intermediates) can be achieved for dry reforming of methane over Ni/CeO₂-nanorod, leading to less coke accumulation and thereafter an improved overall catalytic performance. Therefore, the stability of catalysts for dry reforming reactions can be improved through accelerating the rate of carbon oxidation or slowing down the rate of carbon generation, shedding a new light on tuning the catalytic performance of Ni-based heterogeneous catalysts.