This research investigates the effect of metal particle size on carbon formation and carbon oxidation during dry reforming of methane over Ni/Gd-doped ceria catalysts. Dry reforming of methane (DRM, CH4 + CO2 2CO + 2H2) is an attractive process for syngas production from methane and carbon dioxide, the two major greenhouse gases. The application of this process, however, is limited because of the rapid catalyst deactivation caused by carbon buildup, especially on transition-based catalysts like nickel. Gadolinium-doped ceria (GDC, Gd0.1Ce0.9O1.95), a ceramic material with high oxygen ion conductivity, is a promising catalyst support for DRM as it could provide oxygen ions for Ni metal to oxidize carbon. Our previous work has shown that oxygen ion conductivity improved catalyst activity but was not conclusive on reducing carbon deposition. Carbon accumulation will be prevented when the rate of oxygen transport and oxidation rate of carbon are greater than the rate of carbon formation. A high metal-support interface is necessary for the efficient transportation of oxygen from GDC to the metal surface. A large metal-support interface can be achieved by preparing a catalyst with high metal dispersion or small metal particle size. This work examines how the metal particle sizes and metal-support interfaces influence carbon gasification efficiency as well as catalytic activity and stability. By varying the Ni metal loadings and catalyst preparation methods (wet impregnation, co-precipitation, deposition-precipitation, strong electrostatic adsorption), Ni catalysts supported on GDC with different Ni particle sizes are prepared. We aim to provide an insightful understanding of the relationship of between metal particle size, metal-support interface, carbon formation, and carbon removal by oxygen vacancies of GDC in methane dry reforming.
