Local Structures of Copper Ion Catalysts Anchored onto Various Oxide Supports and their Photocatalytic Reactivities for the Decomposition of N₂O at 298 K. In Situ XAFS, Photoluminescence, EPR Investigations

Abstract
Cu⁺/(SiO₂/Al₂O₃), Cu⁺/Al₂O₃ and Cu⁺/SiO₂ catalysts were prepared by a combination of the ion-exchange method and thermovacuum treatment. In-situ XANES and EXAFS investigations of the catalysts have revealed that Cu⁺ ions are anchored onto Al₂O₃ or SiO₂ as planar 3-coordinate Cu⁺, while being anchored onto SiO₂/Al₂O₃ as linear 2-coordinate Cu⁺. Photoluminescence measurements of the catalysts and their quenching by the addition of N₂O indicated that the Cu⁺ ions interact with N₂O in their photo excited state (3d⁹4s¹). 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. Reaction proceeds more efficiently on the Cu⁺/(SiO₂/Al₂O₃) catalyst than on the Cu⁺/Al₂O₃ or Cu⁺/SiO₂ catalysts, suggesting that the 2-coordinate Cu⁺ species show the higher activity for the photocatalytic decomposition of N₂O than the 3-coordinate Cu⁺ species.