Low‐Temperature H2 Reduction of Copper Oxide Subnanoparticles

• Published in: Chemistry : a European journal Vol. 27; no. 33; pp. 8452 - 8456
• Main Authors: Sonobe, Kazutaka, Tanabe, Makoto, Imaoka, Takane, Chun, Wang‐Jae, Yamamoto, Kimihisa
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 10.06.2021
• Subjects: Catalysts; Chemical reduction; Chemistry; Copper; Copper oxides; dendrimers; Electron states; Elongation; Fine structure; Heavy metals; mesoporous silica; metal oxides; Oxidation; oxidation reactions; Redox properties; Transition metals; Ultrastructure
• ISSN: 0947-6539; 1521-3765; 1521-3765
• DOI: 10.1002/chem.202100508

Subnanoparticles (SNPs) with sizes of approximately 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 oxidation 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 Cu28Ox SNPs, which were prepared by using a dendritic phenylazomethine template, during temperature‐programmed reduction (TPR) with H2 achieved lowering of the temperature (T50=138 °C) reported thus far for the CuII→CuI reduction reaction because of Cu−O bond elongation in the ultrasmall copper oxide particles. The lowering of the CuII→CuI reduction temperature for subnano CuO particles (ca. 1 nm) was demonstrated, compared to the nanoparticles, which was monitored by in situ XAFS H2‐TPR experiments. The enhanced performance with a release of the atomic oxygen from the copper oxide is attributed to the surface‐strained structure and the elongation of the Cu−O bonds.