Interaction of NH₃ with Cu-SSZ-13 Catalyst: A Complementary FTIR, XANES, and XES Study

In the typical NH₃–SCR temperature range (100–500 °C), ammonia is one of the main adsorbed species on acidic sites of Cu-SSZ-13 catalyst. Therefore, the study of adsorbed ammonia at high temperature is a key step for the understanding of its role in the NH₃–SCR catalytic cycle. We employed different spectroscopic techniques to investigate the nature of the different complexes occurring upon NH₃ interaction. In particular, FTIR spectroscopy revealed the formation of different NH₃ species, that is, (i) NH₃ bonded to copper centers, (ii) NH₃ bonded to Brønsted sites, and (iii) NH₄⁺·<i>n</i>NH₃ associations. XANES and XES spectroscopy allowed us to get an insight into the geometry and electronic structure of Cu centers upon NH₃ adsorption, revealing for the first time in Cu-SSZ-13 the presence of linear Cu⁺ species in O_fw–Cu–NH₃ or H₃N–Cu–NH₃ configuration