Effect of sodium nitrate on microwave-assisted synthesis of ceria nanocubes

Fluorite-structured cerium oxide (ceria; CeO_2-x, 0≤x<0.5) possesses unique catalytic activity to promote redox reactions. Among the most common facets of ceria, the {100} facets of ceria nanocubes have been found to be more catalytically active as well as better noble metal supports than the {111} facets of ceria nanopolyhedra. Here we report a facile microwave-assisted synthesis of ceria nanocubes using sodium nitrate as the surface modifying agent (SMA). Microwave methods directly scaled from conventional hydrothermal parameters were found to produce mixtures of ceria nanocubes and ceria nanorods. The effect of sodium nitrate on the shape-control growth of ceria nanocubes was investigated by using various mole ratios of sodium nitrate to the cerium nitrate precursor in the synthetic study. From our morphological analysis of resulting ceria products, the mechanistic roles of the SMA were postulated to destabilize the growth of {110} and {111} facets of ceria nanocrystals as well as influencing the incorporation rate of precursors on the surfaces of ceria crystals.