Real-time optical observation of morphological change of small supported copper particles during redox treatments

Abstract

In situ optical observation was used as a technique to study the effects of cyclic oxidation and reduction (redox) treatment made at temperatures below 673 K on small copper particles supported on porous glass. The in situ real-time observation revealed decreases both in size of copper particles and volume fraction of metallic copper during the cyclic redox treatment. The decreases correspond to an increase in fraction of nonmetallic copper species on the support surface. This is confirmed by comparing the measured with calculated optical spectra and tracing the change in the rate of oxidation of copper particles. This phenomenon is enhanced by using 500 ppm O 2 rather than 1% O 2, and at higher temperatures. The role of a lower oxygen concentration in the mechanism of the phenomenon is discussed.