Photocatalytic Decomposition of N2O into N2and O2at 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

Cu(I) (Cu + ) ion catalysts anchored onto various oxides (SiO 2 ·Al 2 O 3, Al 2 O 3, and SiO 2 ) 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 SiO 2 ·Al 2 O 3, while they exist as planar three-coordinate Cu + on Al 2 O 3 or SiO 2 . It was also found that the typical photoluminescence observed at 430 nm for the Cu + /(SiO 2 ·Al 2 O 3 ) catalyst and that observed at 510 nm for the Cu + /Al 2 O 3 and Cu + /SiO 2 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 N 2 O onto the Cu + ion catalyst leads to the quenching of the photoluminescence of Cu +, indicating that N 2 O interacts with the photoexcited Cu + ion. UV irradiation of the catalysts in the presence of N 2 O led to the formation of N 2 and O 2 at 298 K, indicating that the photocatalytic decomposition of N 2 O proceeds on the Cu + ion catalysts. The reaction was found to proceed more efficiently on the Cu + /(SiO 2 ·Al 2 O 3 ) catalyst than on the Cu + /Al 2 O 3 or Cu + /SiO 2 catalysts, suggesting that the two-coordinate Cu + species show higher activity for this reaction than the three-coordinate Cu + species.