Surface and Inner Defects in Au/CeO₂ WGS Catalysts: Relation between Raman Properties, Reactivity and Morphology

Abstract

Defects (O vacancies) with different Raman properties (A–C, see graphic) and reactivity are present on Au/CeO2. A is Raman inactive, located in external layers, able to form O22− species with O2; B, formed by a Au‐catalysed reduction in H2, is Raman active, located in non‐stoichiometric surface layer, and reacts with O2 without forming O22− species; C is Raman active, located in inner positions, and gives negligible reactivity upon O2. Only A and B defects react with H2O.

Au/TiO2-CeO2 Catalysts for Photocatalytic Water Splitting and VOCs Oxidation Reactions

“…This could be due to a less crystalline and more defective structure of ceria in the presence of gold. In fact, Raman has been reported to be sensitive to the degree of crystallinity of samples, with broader, less intense Raman peaks in the case of less crystalline material [56]. Figure 3c shows the position of the main vibrational mode of anatase Eg, pointing out that there was only a slight red shift (about 2 cm −1 ) on the TiO2-10%CeO2 and Au/TiO2-10%CeO2 samples.…”

“…This could be due to a less structure of ceria in the presence of gold. In fact, Raman has been degree of crystallinity of samples, with broader, less intense Ram crystalline material [56]. Figure 3c shows the position of the main vibrational mode of an was only a slight red shift (about 2 cm −1 ) on the TiO2-10%CeO2 and considering that the Eg anatase mode at 148 cm −1 is associated with th of CeO2 in the TiO2 lattice could probably cause a bond distortion re the vibration band.…”

“…This could be due to a less crystalline and more defective structure of ceria in the presence of gold. In fact, Raman has been reported to be sensitive to the degree of crystallinity of samples, with broader, less intense Raman peaks in the case of less crystalline material [56]. Au/TiO2-10%CeO2 sample, the peak associated with cubic CeO2 was less to lower frequencies compared to over the TiO2-10%CeO2 sample ( Figure respectively).…”

Gold Clusters and Nanoparticles Stabilized by Nanoshaped Ceria in Catalysis

“…These surface oxygen vacancies have also been studied by Raman spectroscopy in combination with HRTEM by Vindigni et al [19], who proposed three families of oxygen vacancies. The first family locates at the external surfaces and readily reacts with O 2 with the formation of O 2 − 2 species.…”

Preparation, characterization of a ceria loaded carbon nanotubes nanocomposites photocatalyst and degradation of azo dye Acid Orange 7

“…Ceria (CeO 2 ) is one of the rare earth oxides that has widely been used in the water gas shift reaction (Rodriguez et al 2007, Vindigni et al 2011, automotive three-way catalytic converters (Matsumoto 2004), green phosphors (Long et al 2006), oxygen storage material (Campbell et al 2005, Esch et al 2005, solid fuel cells (Park et al 2000) and antioxidants in biological model systems (Karakoti et al 2010, Singh et al 2011 due to its unique cubic fl uorite structure (Trovarelli 2002), oxygen storage capacity (Walton 2011) and high activity.…”