Low-Temperature H2 Reduction of Copper Oxide Subnanoparticles.

Subnanoparticles (SNPs) with sizes of ~1 nm are attractive for enhancing the catalytic performance of transition metals and their oxides. Such SNPs are of particular interest as redox-active catalysts in selective oxidative reactions. However, the electronic states and oxophilicity of copper oxide SNPs are still a subject of debate in terms of their redox properties during oxidation reactions for hydrocarbons. In this work, in situ X-ray absorption fine structure (XAFS) measurements of Cu 28 O x SNPs, which were prepared using a dendritic phenylazomethine template, during temperatureprogrammed reduction (TPR) with H 2 achieved lowering of the temperature ( T 50 = 138 °C) reported thus far for the Cu(II) → Cu(I) reduction reaction because of Cu-O bond elongation in the ultrasmall copper oxide particles.