In this paper, copper-doped ceria oxides with different hollowness and size are fabricated by changing the Cu²⁺ doping concentration in the mixed water-glycol system. Results show that the copper-doped CeO₂ oxides undergo a morphology transformation from the solid nanospheres to core–shell, then to hollow nanospheres with the increase of the Cu²⁺ doping concentration. The corresponding size becomes smaller during this transfer process. The Cu²⁺ doping induced acceleration in the nucleation and growth process is further investigated. The resultant Cu²⁺-doped CeO₂ oxides exhibit enhanced CO conversion performance and better reduction behaviors.

In this paper, a simple one-step hydrothermal method has been developed to prepare three-dimensional CeO₂ microflower structures via a cerium oxalate precursor. X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), field-emission scanning electron microscopy (FE-SEM) and thermal gravimetric (TG) analysis were utilized to characterize the products. Herein, unlike the conventional calcination of a cerium oxalate precursor, oxalic acid acted not only as a precipitator but also as a modifier of morphology with a defined amount of C₂O₄ ²⁻, while hydrogen peroxide (H₂O₂) was introduced as an oxidant to make the full conversion from Ce₂(C₂O₄)₃·10H₂O to CeO₂ in the hydrothermal process with the preserved flowerlike morphology. The as-obtained CeO₂ microflowers displayed a high surface area of 147.6 m² g⁻¹ and narrow pore size of 3.759 nm by N₂ adsorption and desorption measurement, and the H₂-TPR test showed its better reduction behavior. Furthermore, CeO₂ microflowers with hierarchical structures presented a higher catalytic activity for CO oxidation.

Surface Cu–O–Ce species can be reduced by CO and active oxygen can easily react with Cu ⁺ –CO to form CO ₂ .

In this paper, a series of well-dispersed nickel–ceria catalysts with high surface area were successfully fabricated using a simple solvothermal approach and characterized by XRD, TEM, EDS, N₂-sorption, Raman and TPR techniques. The results show that the amount of nickel species can have an impact on the morphology of the nickel–ceria catalysts, i.e. the hollow structure, particle size and porous structures. The prepared nickel–ceria samples (with the atomic ratio Ni : Ce (At% (Ni/Ce)) at approximately 6.58%) exhibit high catalytic performance in carbon monoxide (CO) oxidation with 100% conversion at 200 °C. The XRD, Raman, XPS and H₂-TPR data confirm that the nickel species are the main promoting factor in the catalysis, including the doped nickel species, highly dispersed free NiO and the interfacial Ni–[O]–Ce structures. Further, the as-prepared nickel–ceria catalysts show high stability in the catalysis.