Raman Analysis of Mode Softening in Nanoparticle CeO_2−δ and Au-CeO_2−δ during CO Oxidation

Abstract

Oxygen vacancy levels are monitored during the oxidation of CO by CeO(2-δ) nanorods and Au-CeO(2-δ) nanorods, nanocubes, and nanopolyhedra by using Raman scattering. The first-order CeO(2) F(2g) peak near 460 cm(-1) decreases when this reaction is fast (fast reduction and relatively slow reoxidation of the surface), because of the lattice expansion that occurs when Ce(3+) replaces Ce(4+) during oxygen vacancy creation. This shift correlates with reactivity for CO oxidation. Increases in the oxygen deficit δ as large as ~0.04 are measured relative to conditions when the ceria is not reduced.

Effect of Reduction Treatment on CO Oxidation with CeO2 Nanorod‐Supported CuOx Catalysts

“…[30,31] In Au-CeO 2 ,i tw as reported that this firstorder CeO 2 F 2g peak shift correlates with the reactivity for CO oxidation. [30] The most possible location of these oxygen-containingc opper speciess houldb ea tt he CuO x -CeO 2 interface for the reduced 10 wt %C uO x -CeO 2 nanorods sample, probably owing to the abundance of surface oxygen and defects located on the CeO 2 nanorods. Ultimately,t his demands ag reat deal of furtheri nvestigation to understand the oxygen and copperd istribution at the interface with high spatial resolution techniques, which are underway.…”

Effect of Microgravity on Synthesis of Nano Ceria

“…This was attributed to the generation of oxygen vacancies of ceria [32]. Flytzani-Stephanopoulos and colleagues synthesized nano-polyhedra, rods and cubic ceria particles using hydrolysis method and examined its catalytic activity for various reactions [19,[34][35][36][37]. They demonstrated that different shapes of ceria nanoparticles exposing different crystal planes on the catalyst surface significantly influenced the Au dispersion on the ceria support.…”

Hydrogen Production from Chemical Looping Reforming of Ethanol Using Ni/CeO2 Nanorod Oxygen Carrier

“…Li et al [26] reported that Vanadium atom would bond to the surface of CeO 2 -NR by generating V-O-Ce species, thus covering oxygen defects and stabilizing adjacent Ce atoms. The inconspicuous peak at 258.1 cm −1 results from the second order transverse acoustic mode (2TA) or doubly degenerate transverse optical mode (TO), which are Raman inactive in a perfect crystal [27]. The peak at 1179.9 cm −1 may be related to the stretching mode of the short terminal Ce=O.…”

“…The inconspicuous peak at 258.1 cm −1 results from the second order transverse acoustic mode (2TA) or doubly degenerate transverse optical mode (TO), which are Raman inactive in a perfect crystal [27]. The peak at 1179.9 cm −1 may be related to the stretching mode of the short terminal Ce=O.…”