Thermal and UV photo-induced decomposition of azomethane on Rh(111)†
Abstract
The thermal and UV photo-induced decomposition of azomethane, CH3NNCH3, was investigated by means of reflection absorption infrared spectroscopy (RAIRS) and temperature-programmed desorption spectroscopy (TPD). The RAIRS data revealed that azomethane adsorbs in the trans-configuration mode on Rh(111) at 90 K. During thermal treatment, azomethane decomposes exclusively by N–N bond scission, yielding H2, N2, C2N2 and traces of HCN. Upon UV irradiation at 90 K, adsorbed azomethane undergoes tautomerization, forming formaldehyde methylhydrazone, CH3NHNCH2. The important features of the post-irradiation TPD spectra are the significant suppression of C2N2 and N2 formation, and the appearance of the new products methylamine (CH3NH2) and CH4. C–N bond scission also occurred in the illuminated chemisorbed layer at 90 K.