| Abstract
| - Nanocrystalline ceria is under study to improve performance in high-temperature catalysis and fuelcells. We synthesize porous ceria monolithic nanoarchitectures by reacting Ce(III) salts and epoxide-based proton scavengers. Varying the means of pore-fluid removal yields nanoarchitectures with differentpore−solid structures: aerogels, ambigels, and xerogels. The dried ceria gels are initially X-ray amorphous,high-surface-area materials, with the aerogel exhibiting 225 m2 g-1. Calcination produces nanocrystallinematerials that, although moderately densified, still retain the desirable characteristics of high surfacearea, through-connected porosity in the mesopore size range and nanoscale particle sizes (∼10 nm). Theelectrical properties of calcined ceria ambigels are evaluated from 300 to 600 °C and compared to thoseof commercially available nanoscale CeO2. The pressed pellets of both ceria samples exhibit comparablesurface areas and void volumes. The conductivity of the ceria ambigel is 5 times greater than thecommercial sample and both materials exhibit an increase in conductivity in argon relative to oxygen at600 °C, suggesting an electronic contribution to conductivity at low oxygen partial pressures. The ceriaambigel nanoarchitecture responds to changes in atmosphere at 600 °C faster than does the nanocrystalline,non-networked ceria. We attribute the higher relative conductivity of CeO2 ambigels to the bondedpathways inherent to the bicontinuous pore−solid networks of these nanoarchitectures.
- Ceria nanoarchitectures endow the material with faster electrical response times to changes in atmosphere (between O2 and Ar) and higher conductivity at 600 °C for oxygen ion transport than does nanocrystalline ceria of comparable surface area, nanocrystallite size, and void volume. The improved electrical properties of CeO2 ambigels arise from the bonded pathways inherent to the bicontinuous pore−solid networks of the nanoarchitecture.
|
