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

Abstract

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.

Characterisation and reactivity of oxygen species at the surface of metal oxides

“…Transition metal oxides such as Ti- [127,128], Cu- [129][130][131] and V-oxide [132][133][134][135] single site heterogeneous catalysts have been widely constructed in various types of porous materials such as zeolite and also immobilized on various inert oxide supports such as silica. Detailed characterization studies have been carried out at the molecular level by applying various spectroscopies such as UV-Vis, FT-IR and Raman, ESR, XAFS (XANES and FT-EXAFS) and PL spectroscopies.…”

Bulk and Surface Properties of Dispersed CuO Phases in Relation with Activity of NO x Reduction

“…Catalysts based on finely divided copper oxide have displayed interesting activity towards total oxidation of CO, [6][7][8], hydrocarbons [6,9] and alcohols [10,11], and NO x , and SO 2 reduction reactions [3][4][5][6][7][8][9][10][11][12][13][14][15][16]. In the case of selective catalytic reduction of nitrogen oxides (NO x ) by hydrocarbons in an oxygen-rich atmosphere, (HC-SCR process), various catalytic systems based on CuO dispersed with different methods on supports of different nature have been successfully reported in the literature [17][18][19][20][21].…”

Tetragonal Distortion in Thermochromic Copper(II) Diamine Complex Induced by the Fixation on Silica Surfaces and Their Catalytic Investigations

“…/ SiO 2 and [Cu(dieten) 2 ](ClO 4 ) 2 complex in both LT and HT phases. The resonance at *8983 eV is ascribed to the dipole-allowed transition from the Cu 1 s core to the pp level [16][17][18]. The [Cu(dieten) 2 ](ClO 4 ) 2 complex in the LT phase consists of the square-planar unit and the pp intensity should be most enhanced [19].…”