Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5370237 | Applied Surface Science | 2006 | 9 Pages |
Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) is applied to study NH3, adsorbed from the gas phase, and its decomposition products, i.e. NHx species, on Rh nanoparticles, produced by spincoating from a RhCl3 solution in water followed by reduction. A silicon ATR crystal with a hydroxilated SiO2 layer acts as the support for the nanoparticles. Upon exposure to NH3 in the vacuum chamber, NH3 adsorbed to both silica and Rh is detected (sensitivity â¼5 Ã 10â5 absorbance units). Interaction of the NH3 with the silica OH groups is observed around â¼2840 cmâ1 in combination with peaks showing the disappearance of unperturbed OH vibrations between 3500 and 3700 cmâ1. In addition, NH bend vibrations at 1634 cmâ1 and NH stretch vibrations at 3065 and 3197 cmâ1 are observed for substrate temperatures between 20 and 100 °C. The latter two correspond to NH on Rh, as verified with a sample without Rh, and probably correspond to undecomposed NH3. Moreover, they remain after evacuation, suggesting strongly bound species. For a substrate temperature of 75 and 100 °C, additional NH stretch peaks at 3354 and 3283 cmâ1 are observed, possibly due to NH2 intermediates, indicating NH3 decomposition. It is shown that ATR-FTIR can contribute to the sensitive detection of adsorption and decomposition of gaseous species on realistic planar model catalysts.