+ Site Statistics
References:
52,654,530
Abstracts:
29,560,856
PMIDs:
28,072,755
+ Search Articles
+ Subscribe to Site Feeds
Most Shared
PDF Full Text
+ PDF Full Text
Request PDF Full Text
+ Follow Us
Follow on Facebook
Follow on Twitter
Follow on LinkedIn
+ Translate
+ Recently Requested

Oxygen transport in unreduced, reduced and Rh(III)-doped CeO2 nanocrystals



Oxygen transport in unreduced, reduced and Rh(III)-doped CeO2 nanocrystals



Faraday Discussions 134: 377-97; Discussion 399-419



Ceria, CeO2, based materials are a major (active) component of exhaust catalysts and promising candidates for solid oxide fuel cells. In this capacity, oxygen transport through the material is pivotal. Here, we explore whether oxygen transport is influenced (desirably increased) compared with transport within the bulk parent material by traversing to the nanoscale. In particular, atomistic models for ceria nanocrystals, including perfect: CeO2; reduced: CeO1.95 and doped: Rh0.1Ce0.9O1.95, have been generated. The nanocrystals were about 8 nm in diameter and each comprised about 16,000 atoms. Oxygen transport can also be influenced, sometimes profoundly, by microstructural features such as dislocations and grain-boundaries. However, these are difficult to generate within an atomistic model using, for example, symmetry operations. Accordingly, we crystallised the nanocrystals from an amorphous precursor, which facilitated the evolution of a variety of microstructures including: twin-boundaries and more general grain-boundaries and grain-junctions, dislocations and epitaxy, isolated and associated point defects. The shapes of the nanocrystals are in accord with HRTEM data and comprise octahedral morphologies with {111} surfaces, truncated by (dipolar) {100} surfaces together with a complex array of steps, edges and corners. Oxygen transport data was then calculated using these models and compared with data calculated previously for CeO1.97/ YSZ thin films and the (bulk) parent material, CeO197. Oxygen transport was calculated to increase in the order: CeO2 nanocrystal < (reduced) CeO1.95 nanocrystal approximately Rh0.1Ce0.9O1.95 nanocrystal < CeO1.97/YSZ thin film < (reduced) CeO1.97 (bulk) parent material; the mechanism was determined to be primarily vacancy driven. Our findings indicate that reducing one- (thin film) or especially three- (nanocrystal) dimensions to the nanoscale may prove deleterious to oxygen transport. Conversely, we observed dynamic evolution and annihilation of surface vacancies via surface oxygens migrating to the bulk of the nanocrystal; the vacancies left are then filled by other oxygens moving to the surface. Coupled with previous simulation studies, in which we calculated that oxygen extraction from the surface of a ceria nanocrystal was energetically easier compared with the bulk surface, our calculations predict that ceria nanocrystals would facilitate effective oxidative catalysis. This study describes framework simulation procedures, which can be used in partnership with experiment, to explore transport in nanocrystalline ionic systems, which include complex microstructures. Such data can provide predictions for experiment or help reduce the number of experiments required.

(PDF emailed within 1 workday: $29.90)

Accession: 049839007

Download citation: RISBibTeXText

PMID: 17326580


Related references

Analysis of dopant atom distribution and quantification of oxygen vacancies on individual Gd-doped CeO2 nanocrystals. Chemistry 20(21): 6288-6293, 2014

Comparative study of CeO2 and doped CeO2 with tailored oxygen vacancies for CO oxidation. Chemphyschem 12(15): 2763-2770, 2011

Atomic and electronic structure of unreduced and reduced CeO2 surfaces: a first-principles study. Journal of Chemical Physics 120(16): 7741-7749, 2004

Superparamagnetism in iron-doped CeO₂-y nanocrystals. Journal of Physics. Condensed Matter 24(45): 456001, 2012

Suppression of inherent ferromagnetism in Pr-doped CeO₂ nanocrystals. Nanoscale 4(17): 5469-5476, 2012

Surface capping-assisted hydrothermal growth of gadolinium-doped CeO₂ nanocrystals dispersible in aqueous solutions. Langmuir 30(40): 12049-12056, 2014

Oxygen vacancy-induced microstructural changes of annealed CeO2?x nanocrystals. Journal of Raman Spectroscopy 43(1): 76-81, 2012

Sm doped mesoporous CeO2 nanocrystals: aqueous solution-based surfactant assisted low temperature synthesis, characterization and their improved autocatalytic activity. Dalton Transactions 45(4): 1679-1692, 2016

Extra-low-temperature oxygen storage capacity of CeO2 nanocrystals with cubic facets. Nano Letters 11(2): 361-364, 2011

Morphology-dependent interplay of reduction behaviors, oxygen vacancies and hydroxyl reactivity of CeO2 nanocrystals. Physical Chemistry Chemical Physics 17(47): 31862-31871, 2015

Controlled pollination with sorted reduced and unreduced pollen grains reveals unreduced embryo sac formation in Diospyros kaki Thunb. 'Fujiwaragosho'. Journal of the Japanese Society for Horticultural Science 76(2): 133-138, 2007

A DFT+U study on the contribution of 4f electrons to oxygen vacancy formation and migration in Ln-doped CeO2. Physical Chemistry Chemical Physics 18(18): 12938-12946, 2016

Examination of oxygen vacancy formation in Mn-doped CeO2 (111) using DFT+U and the hybrid functional HSE06. Langmuir 29(32): 10120-10131, 2014

Synthesis and characterization of reduced graphene oxide decorated with CeO 2 -doped MnO 2 nanorods for supercapacitor applications. Journal of Colloid and Interface Science 494: 338-344, 2017

NO reduction by CO over CuO supported on CeO2-doped TiO2: the effect of the amount of a few CeO2. Physical Chemistry Chemical Physics 17(24): 16092-16109, 2015