Surface reaction pathways of methylamine on the Ni(111) surface

Abstract

The interaction and bond scission sequence of methylamine, CH3NH2, on Ni(111) have been investigated by means of Auger electron spectroscopy and temperature programmed desorption under UHV conditions in the temperature range 87–800 K. Comparisons have been made to the NH3/Ni(111) and N/Ni(111) systems. Methylamine is found to absorb molecularly through its lone pair up to ∼330 K after which a dehydrogenation channel opens which competes with the desorption channel. The sequence of the initial bond breaking was investigated by measuring the initial reactive sticking coefficient of deuterium labeled molecules at 363 K. Methylamine decomposition was found to take place through both ends of the molecule, initially with a slight rate preference at the C end. The CN residue left on the surface by the dehydrogenation process resulted in self-poisoning of the active sites. This residual species was found to decompose at ∼530 K, leading to N2 desorption and the diffusion of carbon into the crystal at 700–800 K.