Detection of key transient Cu intermediates in SSZ-13 during NH3-SCR deNO  by modulation excitation IR spectroscopy.The small pore zeolite Cu-SSZ-13 is an efficient material for the standard selective catalytic reduction of nitrogen oxides (NO  ) by ammonia (NH3). 
modulation excitation IR spectroscopy
In this work, Cu-SSZ-13 has been studied at 250 °C under high conversion using a modulation excitation approach and analysed with phase sensitive detection (PSD). 
phase sensitive detection (PSD)
While the complementary X-ray absorption near edge structure (XANES) spectroscopy measurements showed that the experiments were performed under cyclic Cu+/Cu2+ redox, Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) experiments provide spectroscopic evidence for previously postulated intermediates Cu-N([double bond, length as m-dash]O)-NH2 and Cu-NO3 in the NH3-SCR deNO  mechanism and for the role of [Cu2+(OH-)]+. 
X-ray absorption near edge structure (XANES) spectroscopy
While the complementary X-ray absorption near edge structure (XANES) spectroscopy measurements showed that the experiments were performed under cyclic Cu+/Cu2+ redox, Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) experiments provide spectroscopic evidence for previously postulated intermediates Cu-N([double bond, length as m-dash]O)-NH2 and Cu-NO3 in the NH3-SCR deNO  mechanism and for the role of [Cu2+(OH-)]+. 
Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS)