“…It is suggested that the more oxygen vacancies and higher surface acidity derived from electron redistribution of Ce and W ions. It can be concluded that an increase in the Brønsted acidity led to higher catalytic activity for CeWTiO x [17].…”
Section: Resultsmentioning
confidence: 96%
“…It is suggested that the more oxygen vacancies and higher surface acidity derived from electron redistribution of Ce and W ions. It can be concluded that an increase in the Brønsted acidity led to higher catalytic activity for CeWTiO x [17]. Figure 3 (a) FTIR spectra (B: Brønsted, L: Lewis), (b) NH 3 -TPD profiles and the amount of NH 3 adsorbed on the acid sites for CeTiO x and CeWTiO x .…”
Section: Resultsmentioning
confidence: 99%
“…Recent studied have revealed that the relation between oxygen vacancies and acidity [15,16]. In our previous study [17], an amorphous CeWTiOx catalyst was synthesised through the sol-gel method, and the improvement of catalytic activity was studied in terms of structural change. It is also necessary to understand the electronic change and acid sites of the catalyst, since the surface acidity is one of the important factor for the catalytic activity.…”
The enhancement of surface acidity for tungsten-doped CeTiO x was investigated through electronic structure. Tungsten doping increased the ratio of Ce 3+ from 12.0% to 29.6%, which was confirmed by XPS. The doped tungsten was present as W 5+ in a ratio of 71.5%. In O K-edge XAS spectra, increase in I eg /I t2g indicated the formation of oxygen vacancies through tungsten doping. The decrease in W 5d-e g peak intensity demonstrated the occupation of the W 5d orbital by electrons formed at the oxygen vacancies. The enrichment of W 5+ was owing to transfer of electrons to 5d-e g orbital of tungsten rather than to cerium ions. The acid sites were analysed using FTIR and NH 3 -TPD. The peak intensity of Brønsted acid sites and amount of NH 3 desorption increased from 66.2 to 136.1 µmol g −1 with tungsten doping. The doped tungsten formed Brønsted acid sites and led to enhanced surface acidity and catalytic activity.
“…It is suggested that the more oxygen vacancies and higher surface acidity derived from electron redistribution of Ce and W ions. It can be concluded that an increase in the Brønsted acidity led to higher catalytic activity for CeWTiO x [17].…”
Section: Resultsmentioning
confidence: 96%
“…It is suggested that the more oxygen vacancies and higher surface acidity derived from electron redistribution of Ce and W ions. It can be concluded that an increase in the Brønsted acidity led to higher catalytic activity for CeWTiO x [17]. Figure 3 (a) FTIR spectra (B: Brønsted, L: Lewis), (b) NH 3 -TPD profiles and the amount of NH 3 adsorbed on the acid sites for CeTiO x and CeWTiO x .…”
Section: Resultsmentioning
confidence: 99%
“…Recent studied have revealed that the relation between oxygen vacancies and acidity [15,16]. In our previous study [17], an amorphous CeWTiOx catalyst was synthesised through the sol-gel method, and the improvement of catalytic activity was studied in terms of structural change. It is also necessary to understand the electronic change and acid sites of the catalyst, since the surface acidity is one of the important factor for the catalytic activity.…”
The enhancement of surface acidity for tungsten-doped CeTiO x was investigated through electronic structure. Tungsten doping increased the ratio of Ce 3+ from 12.0% to 29.6%, which was confirmed by XPS. The doped tungsten was present as W 5+ in a ratio of 71.5%. In O K-edge XAS spectra, increase in I eg /I t2g indicated the formation of oxygen vacancies through tungsten doping. The decrease in W 5d-e g peak intensity demonstrated the occupation of the W 5d orbital by electrons formed at the oxygen vacancies. The enrichment of W 5+ was owing to transfer of electrons to 5d-e g orbital of tungsten rather than to cerium ions. The acid sites were analysed using FTIR and NH 3 -TPD. The peak intensity of Brønsted acid sites and amount of NH 3 desorption increased from 66.2 to 136.1 µmol g −1 with tungsten doping. The doped tungsten formed Brønsted acid sites and led to enhanced surface acidity and catalytic activity.
“…The H 2 consumption and specific surface area were 1110 mmol/g and 103.0 m 2 /g for CT, and 1354 mmol/g and 113.1 m 2 /g for CT_H 2 O 2 , respectively as shown in Table 1 . This is due to the smaller particle size of CT_H 2 O 2 or the formation of dangling bonds due to the disordering of Ce-O [ 31 , 32 , 33 ]. These two facts suggest that the active surface area of CT_H 2 O 2 is larger.…”
Amorphous CeO2-TiO2 nanoparticles synthesized by the H2O2-modified sol-gel method were investigated in terms of the Ce-O-Ce and Ti-O-Ti linkage, local structure, and redox properties. The decrease in the crystallinity of CeO2-TiO2 by H2O2 addition was confirmed. The metal–oxygen linkage analysis showed the difference in size of the metal–oxygen network between crystalline CeO2-TiO2 and amorphous CeO2-TiO2 due to the O22− formed by H2O2. The local structure of CeO2-TiO2 was analyzed with an extended X-ray absorption fine structure (EXAFS), and the oscillation changes in the k space revealed the disordering of CeO2-TiO2. The decrease in Ce-O bond length and the Ce-O peak broadening was attributed to O22− interfering with the formation of the extended metal–oxygen network. The temperature-programmed reduction of the H2 profile of amorphous CeO2-TiO2 exhibited the disappearance of the bulk oxygen reduction peak and a low-temperature shift of the surface oxygen reduction peak. The H2 consumption increased compared to crystalline CeO2-TiO2, which indicated the improvement of redox properties by amorphization.
“…Thus, other additives were also introduced to further enhance the NH3-SCR activity and anti-SO2 poisoning of CeO2/TiO2 via the synergistic effect of components [42], for example, Cu [43], Mo [44], Mn [45] or W [46] et al The W-based composites exhibit excellent electrical, mechanical and thermal properties and the introduction of WO3 could enhance the concentrations of the active oxygen species and acid sites through the synergistic effect of cerium and titanium components, thereby significantly improved the NH3-SCR activity of cerium-titanium mixed oxide catalyst [47][48][49]. Park et al found that the tungsten-doped CeTiOx catalyst could achieve 100% NOx conversion at 250⁓400 °C due to the enhancement of tungsten-doping on its oxygen vacancy and reduction properties [50]. Thus, cerium-tungsten-titanium mixed oxide is a suitable replacement for the conventional V2O5-WO3(MoO3)/TiO2 catalyst owing to the excellent NH3-SCR activity.…”
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