Photocatalytic Decomposition of N2O into N2 and O2 at 298 K on Cu(I) Ion Catalysts Anchored onto Various Oxides. The Effect of the Coordination State of the Cu(I) Ions on the Photocatalytic Reactivity

• Published in: The journal of physical chemistry. B 2000-05, Vol.104 (20), p.4911-4915
• Main Authors: Matsuoka, Masaya, Ju, Woo-Sung, Takahashi, Kenzo, Yamashita, Hiromi, Anpo, Masakazu
• Format: Article
• Language: English
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp9940001

Cu(I) (Cu+) ion catalysts anchored onto various oxides (SiO2·Al2O3, Al2O3, and SiO2) were prepared by the combination of an ion-exchange method and a thermovacuum treatment. XAFS (X-ray absorption fine structure) investigations revealed that Cu+ ions exist as linear two-coordinate Cu+ on SiO2·Al2O3, while they exist as planar three-coordinate Cu+ on Al2O3 or SiO2. It was also found that the typical photoluminescence observed at 430 nm for the Cu+/(SiO2·Al2O3) catalyst and that observed at 510 nm for the Cu+/Al2O3 and Cu+/SiO2 catalysts could be attributed to the radiative decay from the excited electronic state of the linear two-coordinate Cu+ ions and planar three-coordinate Cu+ ions, respectively. The addition of N2O onto the Cu+ ion catalyst leads to the quenching of the photoluminescence of Cu+, indicating that N2O interacts with the photoexcited Cu+ ion. UV irradiation of the catalysts in the presence of N2O led to the formation of N2 and O2 at 298 K, indicating that the photocatalytic decomposition of N2O proceeds on the Cu+ ion catalysts. The reaction was found to proceed more efficiently on the Cu+/(SiO2·Al2O3) catalyst than on the Cu+/Al2O3 or Cu+/SiO2 catalysts, suggesting that the two-coordinate Cu+ species show higher activity for this reaction than the three-coordinate Cu+ species.