Optical observation of oxidation and reduction of small supported copper particles

Abstract

In situ and real-time optical absorption measurements of supported copper particles (4–10 nm) at wavelengths of 300 to 800 nm are carried out under H 2, CO, and O 2 respectively as ambient gases in the temperature range of 300 to 673 K. We observe a reversible change in the optical spectra caused by oxidation of copper and reduction of copper oxide. The data strongly indicate that the oxidation of small copper particles is composed of a fast process of Cu to CuO x ( x ≈ 0.67) and a slow process of CuO x ( x≈ 0.67) to CuO.