Properties of nitrogen-oxygen surface compounds on ZrO₂ samples with different phase compositions according to in situ IR spectroscopy data

The zirconium dioxide surface has a wide variety of adsorption sites differing in their nature. The proportions of these sites can be changed by varying the oxide preparation and pretreatment conditions. This fact shows itself as a wide diversity of surface structures resulting from NO and O₂ adsorption. Under conditions of the selective catalytic reduction of NO_x, the most stable nitrogen oxide species are nitrates that result from the interaction between NO_x and the ZrO₂ surface. The concentrations of the other nitrogen-oxygen surface compounds are two orders of magnitude lower. The routes of NO₃^- formation and decomposition on the ZrO₂ surface are discussed. In these routes, monodentate nitrates (which show themselves at 1550-1555 cm^-1) are considered as intermediates in the formation and decomposition of bidentate NO₃^-.