<p>To overcome the challenges of high temperatures and incomplete pyrolysis in conventional methods for preparing CeO₂, a study was conducted on the preparation of CeO₂ via spray drying and thermal decomposition of cerium chloride solutions. Based on the thermodynamic investigation and thermal behavior study of cerium chloride thermal decomposition, the thermal decomposition mechanisms of the precursor obtained from cerium chloride spray drying were revealed, and its low-temperature thermal decomposition mechanism was investigated. Experimental results indicated that the thermal decomposition of the cerium chloride precursor prepared by spray drying could be completed at just 400&#xa0;°C, which is significantly lower than the temperature required by traditional thermal decomposition methods. The CeO₂ obtained from this process exhibited a chlorine content of only 70.51&#xa0;ppm and displayed a relatively uniform spherical particle morphology. Microstructural characterization reveals that the precursor particle size did not change significantly during heat treatment. However, due to the release and escape of internal gases, its dense solid structure gradually evolved into a loose and porous morphology. This transformation markedly enhanced the porosity of the particles, creating a larger effective surface area to facilitate optimal interaction between O₂/H₂O and CeCl₃ during the gas–solid reaction. Based on the gas–solid reaction kinetic model, such a porous structure reduces diffusion resistance and enhances interfacial mass transfer efficiency, thereby promoting the conversion of CeCl₃ to CeO₂ under thermodynamically favorable conditions.</p> Graphical Abstract <p></p>