THE ADSORPTION AND DECOMPOSITION OF METHYLAMINE ON PD(111)

The thermal decomposition of methylamine (CH3NH2) on a clean Pd{111} surface has been investigated using X-ray photoelectron spectrometry (XPS), secondary ion mass spectrometry (SIMS) and thermal desorption spectrometry (TDS). We find that methylamine undergoes only a dehydrogenation reaction on Pd{111} upon thermal treatment. The TDS and SIMS data from deuterium labeled d3-methylamine indicate that the methyl-hydrogens (H-CH2NH2) are more stable than amino-hydrogens (CH3NH-H). The decomposition products detected by TDS are H-2 and HCN, and there is no influence of coverage on the reaction pathway. The stable surface intermediates identified by XPS and SIMS are CH3NHads, CH2Nads, CHNads and CNads, and no C-N bond activation is observed. No evidence of s-triazine formation is found in the thermal decomposition process. All adsorbed species desorb by 500 K. An adsorption geometry of CHxNads is proposed from the evaluation of XPS and SIMS results.