Supercharged Low-Temperature Oxygen Storage Capacity of Ceria at the Nanoscale.

We provide an explanation for the experimental finding of a dramatically enhanced low-temperature oxygen storage capacity for small ceria nanoparticles. At low temperature, small octahedral ceria nanoparticles will be understoichiometric at both oxidizing and reducing conditions without showing explicit oxygen vacancies. Instead, rather than becoming stoichiometric at oxidizing conditions, such particles are stabilized through oxygen adsorption forming superoxo (O2(-)) ions and become in this way supercharged with oxygen. The supercharging effect is size-dependent and largest for small nanoparticles where it gives a direct increase in the oxygen storage capacity and simultaneously provides a source of active oxygen species at low temperatures.