Ceria Nanoparticles’ Morphological Effects on the N2O Decomposition Performance of Co3O4/CeO2 Mixed Oxides

Abstract

Ceria-based oxides have been widely explored recently in the direct decomposition of N2O (deN2O) due to their unique redox/surface properties and lower cost as compared to noble metal-based catalysts. Cobalt oxide dispersed on ceria is among the most active mixed oxides with its efficiency strongly affected by counterpart features, such as particle size and morphology. In this work, the morphological effect of ceria nanostructures (nanorods (ΝR), nanocubes (NC), nanopolyhedra (NP)) on the solid-state properties and the deN2O performance of the Co3O4/CeO2 binary system is investigated. Several characterization methods involving N2 adsorption at −196 °C, X-ray diffraction (XRD), temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (ΤΕΜ) were carried out to disclose structure–property relationships. The results revealed the importance of support morphology on the physicochemical properties and the N2O conversion performance of bare ceria samples, following the order nanorods (NR) > nanopolyhedra (NP) > nanocubes (NC). More importantly, Co3O4 impregnation to different carriers towards the formation of Co3O4/CeO2 mixed oxides greatly enhanced the deN2O performance as compared to bare ceria samples, without, however, affecting the conversion sequence, implying the pivotal role of ceria support. The Co3O4/CeO2 sample with the rod-like morphology exhibited the best deN2O performance (100% N2O conversion at 500 °C) due to its abundance in Co2+ active sites and Ce3+ species in conjunction to its improved reducibility, oxygen kinetics and surface area.

K-Modified Co–Mn–Al Mixed Oxide—Effect of Calcination Temperature on N2O Conversion in the Presence of H2O and NOx

“…Based on our recent XPS study using appropriate standards [14,26,34] and work [35], we assigned the component with lower BE (780 eV) to tetrahedral Co 2+ and the component with higher BE (782 and 783.5 eV) to octahedral Co 3+ . However, in the literature can also be found opposite assignment [36][37][38][39]. These findings could be explained by the position of maxima for Co(OH) 2 , which is located at the position of second fitting peak of Co 3 O 4 [32].…”

Facet-Dependent Reactivity of Fe2O3/CeO2 Nanocomposites: Effect of Ceria Morphology on CO Oxidation

“…The Fe2O3/CeO2-NX mixed catalysts were prepared by the wet impregnation method, employing an aqueous solution of Fe(NO3)3•9H2O, in order to obtain an atomic ratio Fe/(Fe+Ce) of 0.2, which corresponds to a Fe loading of 7.5 wt.%. This particular ratio was dictated from our previous studies over a series of MOx/CeO2 catalysts where the M/(M + Ce) atomic content is always kept constant to 0.2 [18,78]. Moreover, relevant literature studies over FeOx/CeO2 catalysts revealed that optimum redox/surface properties can be obtained at similar metal contents, e.g.…”

Recent Advances on the Rational Design of Non-Precious Metal Oxide Catalysts Exemplified by CuOx/CeO2 Binary System: Implications of Size, Shape and Electronic Effects on Intrinsic Reactivity and Metal-Support Interactions

“…On the other hand, metal oxides (MOs) prepared from earth-abundant, and inexpensive transition metals have attracted considerable attention as alternatives to rare and expensive NMs, due to their particular features, such as enhanced redox properties, thermal stability and catalytic performance in conjunction to their lower cost [2,3,5,[28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43]. The latter is clearly manifested in Figure 1, which schematically depicts the cost of noble metals in comparison with copper (a typical transition metal massively involved in MOs) for the past five-year period.…”