Abstract
Ceria has been widely studied either as catalyst itself or support of various active phases in many catalytic reactions, due to its unique redox and surface properties in conjunction to its lower cost, compared to noble metal-based catalytic systems. The rational design of catalytic materials, through appropriate tailoring of the particles’ shape and size, in order to acquire highly efficient nanocatalysts, is of major significance. Iron is considered to be one of the cheapest transition metals while its interaction with ceria support and their shape-dependent catalytic activity has not been fully investigated. In this work, we report on ceria nanostructures morphological effects (cubes, polyhedra, rods) on the textural, structural, surface, redox properties and, consequently, on the CO oxidation performance of the iron-ceria mixed oxides (Fe2O3/CeO2). A full characterization study involving N2 adsorption at –196 °C, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), temperature programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS) was performed. The results clearly revealed the key role of support morphology on the physicochemical properties and the catalytic behavior of the iron-ceria binary system, with the rod-shaped sample exhibiting the highest catalytic performance, both in terms of conversion and specific activity, due to its improved reducibility and oxygen mobility, along with its abundance in Fe2+ species.
Highlights
Ceria (CeO2 ), or cerium oxide, has been extensively used in a variety of catalytic applications such as oxidation processes, steam reforming, water-gas shift reaction, reduction of NOx, among others [1,2,3].Ceria’s unique properties, such as improved thermal stability, high oxygen storage capacity (OSC), and oxygen mobility render it an exceptional component for ceria-based catalytic materials [2,4,5,6]
Sudarsanam et al [40] studied the role of support morphology in copper-ceria and iron-ceria nanorods for diesel soot combustion, and revealed an abundance in oxygen vacancies in both catalytic systems, with copper-ceria nanorods, exhibiting the best catalytic performance, which was ascribed to the high reducibility of ceria and the large amount of acid sites
In view of this fact, the above statements regarding structure–function relationships can be further corroborated by the perfect relationship between the catalytic performance and the surface-to-bulk ratio (Os /Ob ) (Figure 9), as it has been reported by our group [18] for CO oxidation in copper-ceria samples
Summary
Ceria (CeO2 ), or cerium oxide, has been extensively used in a variety of catalytic applications such as oxidation processes, steam reforming, water-gas shift reaction, reduction of NOx, among others [1,2,3]. Sudarsanam et al [40] studied the role of support morphology in copper-ceria and iron-ceria nanorods for diesel soot combustion, and revealed an abundance in oxygen vacancies in both catalytic systems, with copper-ceria nanorods, exhibiting the best catalytic performance, which was ascribed to the high reducibility of ceria and the large amount of acid sites. Namely N2 adsorption at –196 ◦ C (Brunauer–Emmett–Teller (BET) method), X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature programmed reduction using H2 (H2 -TPR), and X-ray photoelectron spectroscopy (XPS), have been employed in order to gain insight into the effect of support morphology on the textural, structural, redox, surface properties and, on the catalytic performance of the iron-ceria binary system. The oxidation of CO was employed as probe reaction in order to disclose structure–activity relationships
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