Experimental and theoretical characterization of NOx species on Ag/α-Al2O3

The adsorption of NOx species on α-alumina and Ag/α-alumina is investigated by in situ diffuse reflection infrared Fourier transform (DRIFT) spectroscopy and density functional theory (DFT) calculations. The vibrational spectra obtained by DRIFTS experiments show broad spectral bands in the range between 1650 and 1200 cm−1. The absence of distinct features is attributed to the heterogeneity of powder samples, i.e., variation in Ag cluster size and α-alumina surface termination. DFT calculations are employed to evaluate ground-state structures and vibrational wavenumbers of different NOx species adsorbed either on alumina or Ag1–Ag4 clusters supported on alumina. In agreement with experiments, Ag cluster size and surface termination strongly influence the calculated vibrational properties. Although, an unambiguous identification of surface species from the DRIFT spectra is difficult, the theoretical results provide valuable guidance. As such, this approach has the potential to further increase the understanding of the reaction mechanism during hydrocarbon assisted selective catalytic reduction (HC-SCR) of NOx.

The adsorption of NOx species on α-alumina and Ag/α-alumina is investigated by in situ diffuse reflection infrared Fourier transform (DRIFT) spectroscopy and density functional theory (DFT) calculations.Figure optionsDownload as PowerPoint slide