In situ measurement of the redox behavior of individual ceria zirconia nanoparticles

Ceria zirconia solid solution nanopowders have been widely used as automobile three-way catalysts to adjust the local oxygen environment in order to reduce pollution. The correlations between the structure, chemistry, and reducibility of individual ceria zirconia nanoparticles were studied and the critical factors that may improve their performance were identified. Nanoparticles with similar size were sometimes observed to have different redox property. A comparison of reduction behavior of two particles as a function of temperature confirmed that activity in one particle was higher as its oxidation state changed from 4 to 3 while negligible change was observed for the other. Structure of one particle had changed during ex-situ heat treatment in reducing environment, probably due to oxygen vacancy ordering. Statistical measurements obtained from 10 individual particles showed that the activity of Ce might be directly related to the variation in local chemical composition (Ce/Zr ratio) and dropped with increasing Ce concentration. This is an abstract of a paper presented at the 2007 AIChE Annual Meeting (Salt Lake City, UT 11/4-9/2007).