Rational Design of Mesoporous CuO-CeO₂ Catalysts for NH₃-SCR Applications Guided by Multiple In Situ Spectroscopies

Efficient nontoxic catalysts for low-temperature NH₃ selective catalytic reduction (NH₃-SCR) applications are of great interest. Owing to their promising redox and low-temperature activity, we prepared CuO-CeO₂ catalysts on a mesoporous SBA-15 support using targeted solid-state impregnation (SSI), guided by multiple in situ spectroscopy. The use of template P123 allowed dedicated modification of the surface properties of the SBA-15 matrix, resulting in a changed reactivity behavior of the metal precursors during the calcination process. To unravel the details of the transformation of the precursors to the final catalyst material, we applied in situ diffuse reflectance infrared Fourier transform (DRIFT), UV-visible (UV-vis), and Raman spectroscopies as well as online Fourier transform infrared (FTIR) monitoring of the gas-phase composition, in addition to ex situ surface, porosity, and structural analysis. The in situ analysis reveals two types of nitrate decomposition mechanisms: a nitrate-bridging route leading to the formation of a CuO-CeO₂ solid solution with increased low-temperature NH₃-SCR activity, and a hydrolysis route, which facilitates the formation of binary oxides CuO + CeO₂ showing activity over a broader temperature window peaking at higher temperatures. Our findings demonstrate that a detailed understanding of catalytic performance requires a profound knowledge of the calcination step and that the use of in situ analysis facilitates the rational design of catalytic properties.