Monitoring
surface species and their bonding structures in link
to specific chemical processes has long been an active, important
subject in heterogeneous catalysis. In this article, with employment
of temperature-programmed reaction/desorption, reflection–absorption
infrared spectroscopy, Auger electron spectroscopy, and X-ray photoelectron
spectroscopy in combination with density functional theory computation,
we present three CH<sub>3</sub>CN formation channels from reaction
of CH<sub>2</sub>CN generated by ICH<sub>2</sub>CN dissociative adsorption
on Cu(100) and first spectroscopic evidence for CHCN on single crystal
surfaces. The CH<sub>3</sub>CN formation mechanisms are dependent
on CH<sub>2</sub>CN adsorption geometries. At lower coverages, CH<sub>2</sub>CN is adsorbed with the C–C–N approximately
parallel to the surface. Reaction of these adsorbates produces CH<sub>3</sub>CN via first- and second-order kinetics, with the largest
desorption rates occurring at 213 K and ∼400 K, respectively.
At or near a saturated first-layer coverage, decomposition of ICH<sub>2</sub>CN forms C-bonded CH<sub>2</sub>CN (−CH<sub>2</sub>CN), which then transforms to N-bonded −NCCH<sub>2</sub> with
tilted orientation. Disproportionation of the −NCCH<sub>2</sub> generates CH<sub>3</sub>CN at ∼324 K. Thermal products of
H<sub>2</sub>, HCN and (CN)<sub>2</sub> evolving at higher temperatures
are originated from the CHCN dissociation. On oxygen-precovered Cu(100),
reaction of CH<sub>2</sub>CN forms new surface intermediates of vertical
−NCO and −CCO, in addition to perturbed CH<sub>3</sub>CN desorption. In the conditions studied, formation of H<sub>2</sub>, HCN, and (CN)<sub>2</sub> is terminated due to the presence of
preadsorbed O. −NCO and −CCO on O/Cu dissociate at ∼525
and 610 K, respectively, into CO and CO<sub>2</sub>