Critical Role of Interfacial Sites between Nickel and CeO2 Support in Dry Reforming of Methane: Revisit of Reaction Mechanism and Origin of Stability

摘要

Dry reforming of methane (DRM) is one of the effective catalytic routes to utilize methane and carbon dioxide molecules. The supported Ni catalysts on lanthanide oxides show remarkable reactivities and stabilities in DRM. However, it remains inconclusive regarding the mechanism and origin of stability of supported Ni catalysts. In this work, first-principles density functional theory (DFT) calculations are performed to investigate the catalytic properties of CeO2-supported Ni-based catalyst. The reactivities of several sites including metal, support, interface, and vacancy on support and interface are evaluated on the same footing for the activation of reactants, CH4 and CO2. The distinct features revealed from comparisons provide the decisive proof to identify the active sites in DRM. Moreover, the different routes leading to the formation of products of H-2 and CO are described. Besides CO2 dissociation, CO is also possibly formed from the successive oxidation of CH*. The stability of catalysts is attributed to the facile elimination of cokes, which are mostly consumed by the interfacial oxygen. The calculations also indicate the inadequate description provided by the current accepted mechanism of supported Ni. Instead, an updated reaction mechanism is proposed, which is consistent with the experimental observations and underscores the importance of interface. The current work not only deepens the understanding of catalytic properties of supported Ni catalysts in DRM but also signifies the effectiveness of interface engineering for the improvement of catalytic performance.