Mechanistic Insights into the Role of CH4 and CO2 Activation in Dry Reforming of Methane over Ni/CeO2 Catalysts with Different Crystal Planes

The activation of CH4 and CO2 as well as the formation of carbon deposit are crucial for dry reforming of methane (DRM), and mechanistic insights into the relationship between reactant activation and carbon evolution during the DRM process are expected to provide guidance for the design of high-performance catalysts. Herein, by utilizing carefully defined Ni/CeO2 model catalysts with different CeO2 crystal planes, we elucidate at the atomic scale the roles of crystal plane in determining the reactant activation and carbon deposit formation in DRM by a joint experimental–theoretical method. The crystal planes of CeO2 determine the active sites and activation ability for CH4 and CO2 by influencing Ni–CeO2 interactions and oxygen vacancy (OV) concentrations. Both the metal and interface active sites of Ni/CeO2(111) and Ni/CeO2(110) can activate CH4 and exhibit good DRM activity. In contrast, only the metal site on Ni/CeO2(100) can activate CH4, leading to a reduced DRM activity. The relatively balanced CH4 and CO2 activation pathways for Ni/CeO2(110) and Ni/CeO2(100) catalysts ensured the stability of the catalysts, whereas Ni/CeO2(111) was rapidly deactivated due to carbon deposits. This study provides insights into the roles of metal–support interactions and OV sites on catalysts for CH4 dissociation activity, CO2 activation, and carbon deposit elimination in the DRM process, which can provide valuable guidance for the design of efficient catalysts with high activity and stability in DRM.