Ceria Nanostructures Obtained by Hydrothermal Synthesis: Exploring the Experimental Parameter Landscape for Precise Morphology and Size Control

Many oxidation catalysts rely on ceria nanomaterials as efficient supports for platinum group metal nanoparticles, where morphology affects the catalytic performance. Rational exploitation of the chemical parameter space enables the tuning and control of these morphological features. This study presents a systematic investigation of conventional and microwave-assisted hydrothermal syntheses of ceria nanorods and nanocubes. The specific role of Ce(III) counter-ions in nanorod formation was systematically investigated, identifying chloride ions as essential for anisotropic growth. Microwave heating proved superior to conventional methods, yielding high-aspect-ratio rods in 10 min while preventing the surface area loss associated with thermal coarsening. For the nanocubes, an acid-buffered route was developed to narrow the polydispersity. The reactor filling ratio in the microwave syntheses emerged as a key parameter to modulate solvent evaporation, allowing tuning of the nanocube size (from 14 to 26 nm) and truncation degree. Structural and morphological characterisation by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller specific surface area analysis (BET) confirmed the formation of highly crystalline and porous nanomaterials, providing a rational framework for the synthesis of ceria nanostructures with controlled morphology via microwave-assisted heating. The effect of autogenous pressure was rationalised by numerical calculations using a Python script developed by the authors.