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Photocatalytic Reaction NO + CO + hν → CO2 + 1/2N2 Activated on ZnO1–x in the UV–Vis Region

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journal contribution
posted on 04.12.2017, 00:00 by Ilya V. Blashkov, Lev L. Basov, Andrey A. Lisachenko
It is shown for the first time that the photocatalytic reaction of NO reduction by CO into N2 can occur on self-sensitized ZnO1–x catalysts upon visible light irradiation (λ > 400 nm) at room temperature with the selectivity reaching 95%. The reaction proceeds in two stages through the intermediate product N2O. The formed CO2 remains on the surface and can be completely desorbed after completion of the photoreaction by heating ZnO1–x up to 820 K. The spectral dependencies of the first and of the second stages repeat the optical absorption spectra of the ZnO1–x intrinsic color centers: the oxygen vacancies having captured one or two electrons (F+ and F centers), the Zn+ ions, and the Zn vacancies having trapped the hole (V centers). High values of quantum yields in the vis region are caused by large (up to 103 s) lifetimes of photoexcited centers.The reaction mechanism is proposed; it includes the following stages: (a) the NO photoadsorption (PA) on the F-type and on V-type centers producing the adsorbed NO and NO2 species, respectively; (b) the reduction of NO and NO2 into N2O and further into N2 by CO which regenerates the donor centers.