THE ADSORPTION AND DECOMPOSITION OF METHYLAMINE ON PD(111)

The thermal decomposition of methylamine (CH3NH2) on a clean Pd{111} s urface has been investigated using X-ray photoelectron spectrometry (X PS), secondary ion mass spectrometry (SIMS) and thermal desorption spe ctrometry (TDS). We find that methylamine undergoes only a dehydrogena tion reaction on Pd{111} upon thermal treatment. The TDS and SIMS data from deuterium labeled d3-methylamine indicate that the methyl-hydrog ens (H-CH2NH2) are more stable than amino-hydrogens (CH3NH-H). The dec omposition products detected by TDS are H-2 and HCN, and there is no i nfluence of coverage on the reaction pathway. The stable surface inter mediates identified by XPS and SIMS are CH3NHads, CH2Nads, CHNads and CNads, and no C-N bond activation is observed. No evidence of s-triazi ne formation is found in the thermal decomposition process. All adsorb ed species desorb by 500 K. An adsorption geometry of CHxNads is propo sed from the evaluation of XPS and SIMS results.