Tuning of Shape, Defects, and Disorder in Lanthanum-Doped Ceria Nanoparticles: Implications for High-Temperature Catalysis

The design of nanomaterials by tailoring the size, shape, and surface chemistry has a significant impact on their properties. The fine-tuning of structural defects of ceria rod-like and cube-like-shaped nanoparticles was performed via La3+ doping in molar ratios of 0-70 mol %. Morphology control was achieved by varying the hydrothermal synthesis temperature. For LaxCe1-xO2-x/2 samples prepared at 110 degrees C, nanorod-like structures are obtained for x < 0.30 and a random morphology of interconnecting polyhedra is achieved for a larger x. The ceria fluorite crystalline structure is maintained at an x of up to 0.60, and both Raman and X-ray diffraction results indicate a high level of defects and disorder in the crystalline structure. For LaxCe1-xO2-x/2 samples prepared at 180 degrees C, cubeshaped particles are predominant for an x of up to 0.10; however, for x > 0.20, two fluorite phases with different lattice parameters are associated with two distinct shapes, cubes and rods The La concentration in nanocubes is limited to x = 0.10 even for samples prepared with higher nominal La concentrations, whereas the nanorods contain larger La concentrations. The demonstrated morphology and defect control on La-doped ceria nanoparticles are critical for applications such as high-temperature oxide catalysts.