Structural Characterization and Catalytic Activity of Nanosized Ceria−Terbia Solid Solutions

Abstract

Structural characteristics and catalytic activity of nanosized ceria-terbia mixed oxides have been investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ion scattering spectroscopy, temperature-programmed reduction/oxidation, and Brunauer-Emmett-Teller surface area techniques. The catalytic usefulness has been evaluated for oxygen storage-release capacity (OSC) and CO oxidation activity. The XRD and TEM results suggest that the crystallite sizes of these nano-oxides are in the range 5-12 nm within the investigated temperature range of 773-1073 K. The mixed oxide solid solutions adopted a fluorite-type structure and exhibited cell parameters with respect to Vegard's rule. The XPS measurements revealed that both cerium and terbium are in 3+ and 4+ oxidation states, 4+ being dominant in both cases. The reduction temperature of the Ce-Tb oxide is observed to be lower than that of the pure ceria and exhibited better redox properties due to the formation of solid solution. The OSC is substantially higher for the mixed oxide, and the presence of oxygen vacancies favored better CO oxidation activity. The nanosized ceria-terbia mixed oxide is also found to be thermally quite stable and capable of manifesting redox behavior after severe heat treatment.

Enhanced Catalytic Activity of Supported Gold Catalysts for Oxidation of Noxious Environmental Pollutant CO

“…It reveals the formation of face-centered cubic (fcc) fluorite type phase of CeO 2 . In the synthesized samples, no prominent peak for any other phase was found demonstrating the high purity of the synthesized product which in turn is in accordance with the literature [19,20]. Literature shows that, on doping metallic cation with radius smaller than Ce 4+ , the peak positions are slightly shifted towards the higher diffraction angles (2 ) [21].…”

Thin Film Deposition of Tb3Al5O12:Ce by Pulsed Laser Ablation and Effects of Low-temperature Post-annealing

“…binding energies of the Tb, Al, O, and Ce were well in agreement with reported values [16]. The Ce 3d feature in (d) shows a complex structure consisting of Ce 3d 5/2 and Ce 3d 3/2 spin-orbit doublet around 885 and 904 eV, respectively, which is a characteristic property of the Ce 3+ ion [17]. This spectral feature confirms that the chemical valence of Ce ions doped in the TAG:Ce thin film is trivalent.…”

The influence of promoters (Zr, La, Tb, Pr) on the catalytic performance of CuO-CeO2 systems for the preferential oxidation of CO in the presence of CO2 and H2O

“…and M 4+ oxidation states, (adopting M 3+ oxidation state more easily than bulk ceria) [28], induces the formation of ordered intrinsic and extrinsic oxygen vacancies thereby enhance the OSC [29,30]. Despite of the doping is a key factor in the OSC, other factors can also influence the reducibility of ceria such as surface area, nature and distribution of dopant, oxygen vacancies and bulk oxygen mobility [31].…”

“…The second step, at about 700 ºC, is attributed to the reduction of the bulk oxide, which should be easier than for pure CeO2,because of the distortion of the framework. The change of Ce 4+ cations by Tb 4+ cations, which have smaller atomic ratio, diminishes the cell volume and favors the reduction [28]. The incorporation of praseodymium into the ceria also shifts the reduction of the ceria towards lower temperature.…”