Study of Self-Sensitization of Wide-Gap Oxides Photocatalysts

ABSTRACT: The self-sensitization of wide-gap oxide photocatalysts to the region beyond the long-wave edge by changing the stoichiometry is discussed. The results of in situ investigations in three phases: gas—adsorbate—surface obtained by a variety of complementary experimental methods are analyzed. Dielectrics (MgO, Al₂O₃, BeO) were sensitized by creating colored F- and V- type photocatalysis centers via the thermal reduction of oxides in a vacuum. For semiconductors, the 2D structures of ZnO/ZnO1−x and TiO2/TiO2−x were formed through surface photo-reduction. In all self-sensitization cases, enhanced photosorption activity was observed. The quantum yields in the model POIE (photo-induced oxygen isotope exchange) redox reaction under VIS illumination of 2D structures and resonant exciton illumination of a layered 2D structure ZnO/ZnO1−x/O− are 5–7 times higher than those of the initial samples. Both 2D structures showed stable activity in the redox reaction  $$\mathrm{CO+NO}\overset{\mathrm{hv}}{\operatorname*{\rightarrow}}1/2\mathrm{N}_{2}\uparrow+\mathrm{CO}_{2\mathrm{ads}}$$ with quantum yields 5–7 times higher than those of the initial oxides in their intrinsic absorption region.