The adsorption of N2 by alumina-supported Rh surfaces has been studied by high-sensitivity infrared transmission methods. For 14N2 on Rh, a single N-N absorption band at 2257 cm-1 is observed at high N2 pressure (218 torr) and at temperatures below about 240 K. This chemisorbed N2 species exhibits an adsorption energy of about 2.2 kcal mol-1, based on infrared studies of the equilibrium situation. Physisorbed N2 on Al2O3 was also detected below 200 K by its infrared spectrum. Its stretching frequency (2331 cm-1) is identical with that of N2(g), indicating a very weak electronic interaction. The adsorption energy for this physisorbed species is about 1.6 kcal mol-1. This work is an example of the usefulness of high-sensitivity IR techniques, coupled with multiple-scan data acquisition methods, for studying weakly absorbing surface species in detail. The work also illustrates the utility of IR cells designed for working at cryogenic sample temperatures and capable of studying support and metal adsorption simultaneously.
|Number of pages||5|
|Journal||Journal of Physical Chemistry|
|Publication status||Published - 1984 Dec 1|
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry