Precursor-mediated reactivity of vibrationally hot molecules: Methane activation on Ir(111)

• DOI: 10.1016/j.cattod.2014.10.025
• Publication Date: 2014-12-05T01:41:20Z
• Authors: Eric Dombrowski; Eric Peterson; Deno Del Sesto; A.L. Utz
• Keywords: 02 engineering and technology; 0210 nano-technology; 7. Clean energy

Abstract Industrial steam reformers use temperatures greater than 1000 K to activate methane dissociation. At these temperatures, typical translational energies (Etrans) are much lower than the energy threshold for reaction, but the majority of methane molecules are vibrationally excited. A combination of molecular beam techniques and state-resolved infrared laser excitation allowed us to quantify reaction probability, S0, for vibrationally excited methane in v = 1 of the ν3 C–H stretching vibration (Evib = 36 kJ/mol) at Etrans ranging from 2 to 48 kJ/mol. On a 1000 K Ir(1 1 1) surface, ν3 excitation enhanced S0 at all Etrans studied, and two distinct reaction channels appeared. When Etrans > 15 kJ/mol, S0 increased with Etrans, as expected for direct dissociative chemisorption. When Etrans