Adsorption and reactions of ICH₂CN on Cu(100) and O/Cu(100)

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 CH₃CN formation channels from reaction of CH₂CN generated by ICH₂CN dissociative adsorption on Cu(100) and first spectroscopic evidence for CHCN on single crystal surfaces. The CH₃CN formation mechanisms are dependent on CH₂CN adsorption geometries. At lower coverages, CH₂CN is adsorbed with the C-C-N approximately parallel to the surface. Reaction of these adsorbates produces CH₃CN 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 ICH₂CN forms C-bonded CH₂CN (-CH₂CN), which then transforms to N-bonded -NCCH₂ with tilted orientation. Disproportionation of the -NCCH₂ generates CH₃CN at ∼324 K. Thermal products of H₂, HCN and (CN)₂ evolving at higher temperatures are originated from the CHCN dissociation. On oxygen-precovered Cu(100), reaction of CH₂CN forms new surface intermediates of vertical -NCO and -CCO, in addition to perturbed CH ₃CN desorption. In the conditions studied, formation of H ₂, HCN, and (CN)₂ 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 CO₂.