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.
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