Hydrothermal Synthesis and in Situ Powder X-ray Diffraction Study of Bismuth-Substituted Ceria Nanoparticles

Ceria is a widely used material for multiple purposes, e.g., as catalysts, sensors, and solid electrolytes. Substitution of Ce with Bi in nanocrystalline ceria facilitates an even broader field of applications. Here we present an easy, reproducible autoclave-based hydrothermal route for preparing phase-pure nanocrystalline bismuth-substituted ceria as well as a continuous flow synthesis method that is suitable for large-scale production. The produced materials were characterized using a wide range of techniques to understand the synthesis-dependent changes in crystallographic structure, crystallite size, optical properties, type and number of surface adsorbed groups, and overall nanostructure. Furthermore, photodecomposition of a model dye compound (rhodamine B) was performed to investigate the photocatalytic properties of the as-synthesized materials. To investigate the formation mechanisms, in situ powder X-ray diffraction data were measured, revealing that miniscule crystallites of BixCe1-xO2-x/2 formed already during mixing of the precursor solutions via coprecipitation at room temperature. Pristine samples with tunable crystallite size and band gaps were obtained, thus demonstrating that the method is viable for tailoring of bismuth-doped ceria with controllable physical properties.