Dissociative adsorption of methane on Pt(111) induced by hyperthermal collisions

Abstract

Measurements have been made of the dissociative adsorption of methane on a Pt(111) surface at surface temperatures of 150 and 550 K using hyperthermal beam techniques. Sticking coefficient measurements made at 550 K are in close agreement with existing literature data. Measurements made at 150 K extend our understanding of the dissociative sticking of methane into a new, low-temperature regime. Reflection–absorption infrared (RAIR) spectral measurements made at 150 K definitively identify the primary product of the dissociative adsorption as the methyl (CH₃) moiety. The thermal evolution of this moiety has subsequently been followed by RAIRS and temperature-programmed desorption (TPD). The observation of the C₂ ethylidyne moiety at temperatures above 300 K provides clear evidence for the formation of C—C bonds during the thermal chemistry of the methyl moiety.