Study of Ag/Ce Nd1-O2 nanocubes as soot oxidation catalysts for gasoline particulate filters: Balancing catalyst activity and stability by Nd doping

Soot Oxidation over CeO2 or Ag/CeO2: Influences of Bulk Oxygen Vacancies and Surface Oxygen Vacancies on Activity and Stability of the Catalyst

“…The lattice fringes of Ag in HRTEM images observed in Figure e, Figure h, and Figure i measured about 0.24 nm, which corresponds to the {111} crystal planes of Ag. AgO x was not observed, corroborating the results obtained by the XRD analysis . Moreover, metallic Ag particles dispersed on the CeO 2 have the same particle size for all the Ag/CeO 2 catalysts as presented in Figure S2, indicating that the effect of Ag particle size on soot catalytic oxidation can be ruled out.…”

“…For the Ag/CeO 2 catalysts, the D bands grow remarkably at the expense of the F 2g mode and redshift to 532 cm –1 , 543 cm –1 , and 571 cm –1 , respectively, after impregnation of Ag, compared with those in the Raman spectra for the CeO 2 catalysts as illustrated in Figure b. These results demonstrate that Ag can promote the generation of V O–b as a result of bulk oxygen diffusing onto the catalyst surface . The I D / I F2g value of Ag/CeO 2 ‐50 given in Table increases dramatically from 0.04 to 0.38, larger than the value of Ag/CeO 2 ‐30, which indicates that the effect of Ag impregnation on V O–b of Ag/CeO 2 ‐50 is greater than those of Ag/CeO 2 ‐30 and Ag/CeO 2 ‐70.…”

“…All the cerium oxides presented in Figure e, Figure g, and Figure k selectively expose {110} and {111} crystal planes as evidenced by their lattice fringes of 0.19 nm and 0.31 nm, respectively . After the impregnation of Ag, the morphologies and sizes of all the Ag/CeO 2 catalysts do not change much , . The lattice fringes of Ag in HRTEM images observed in Figure e, Figure h, and Figure i measured about 0.24 nm, which corresponds to the {111} crystal planes of Ag.…”

“…Ag impregnation remarkably reduces the ratio of Ce 3+ /Ce 4+ , given in Table , and reduces the [V O–s ] for all the CeO 2 due to the reaction between Ag and surface oxygen vacancies (Ag + + Ce 3+ → Ag 0 + Ce 4+ ) , . However, the introduction of Ag onto CeO 2 dramatically increases the ratio of O‐ x to O 2– in catalysts as shown in Table , which is attributed to the activation of O 2 on the Ag , .…”

“…The lower oxygen content and almost no NO x in GDI exhausts make the commercial catalyst, Pt, quite ineffective for removing soot in diesel exhausts . On the basis of some previous studies, CeO 2 and Ag/CeO 2 are considered as promising catalysts in diesel exhausts, and are comparable to the commercial catalyst Pt. Meanwhile, the ability of ceria to deliver active oxygen onto a soot surface from the cerium lattice along with supported silver nanoparticles as an oxygen collector could facilitate catalytic soot oxidation under oxygen‐poor conditions.…”