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 CH₃CN desorption. In the conditions studied, formation of H₂, 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

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 CH₃CN desorption. In the conditions studied, formation of H₂, 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

Study on the Adsorption and Reactions of FCH₂CH₂OH and ClCH₂CH₂OH on Ni(111): Effects of Halogen and Preadsorbed Oxygen

Temperature-programmed reaction/desorption (TPR/D), reflection–absorption infrared spectroscopy (RAIRS), and X-ray photoelectron spectroscopy (XPS) have been employed to investigate the reactions of FCH₂CH₂OH and ClCH₂CH₂OH on Ni(111) and oxygen-precovered Ni(111) (O/Ni(111)). In the chemical process of FCH₂CH₂OH on Ni(111), only FCH₂CH₂O- is found to be the stable reaction intermediate, which starts to appear at ∼190 K. At low coverages, this intermediate decomposes into H₂ and CO. Additional C₂H₄ (219 K) is generated at higher exposures. On Ni(111) at 200 K, ClCH₂CH₂OH mainly dissociates to form ClCH₂CH₂O- and -CH₂CH₂O- at lower exposures, with H₂ and CO as the final products, while ClCH₂CH₂O- becomes predominant at higher exposures and is responsible for the extra C₂H₄ channel of 218 K. C₂H₄ is also generated at 161 and 174 K as the exposure is increased to render multilayer adsorption. Due to the competition in the scission of the carbon–halogen and carbon–hydrogen bonds, ClCH₂CH₂OH has better reactivity toward C₂H₄ formation than FCH₂CH₂OH. No -CH₂CH₂OH is found in the decomposition of FCH₂CH₂OH and ClCH₂CH₂OH on Ni(111), which is the intermediate in the reaction of ICH₂CH₂OH on Ni(100) and Pd(111). The presence of preadsorbed oxygen can enhance the ethylene formation at low coverages of FCH₂CH₂OH and ClCH₂CH₂OH. At higher coverages, additional acetaldehyde is formed in the reaction of FCH₂CH₂OH, in contrast to the ethylene oxide from ClCH₂CH₂OH

Study on the Adsorption and Reactions of FCH₂CH₂OH and ClCH₂CH₂OH on Ni(111): Effects of Halogen and Preadsorbed Oxygen

Temperature-programmed reaction/desorption (TPR/D), reflection–absorption infrared spectroscopy (RAIRS), and X-ray photoelectron spectroscopy (XPS) have been employed to investigate the reactions of FCH₂CH₂OH and ClCH₂CH₂OH on Ni(111) and oxygen-precovered Ni(111) (O/Ni(111)). In the chemical process of FCH₂CH₂OH on Ni(111), only FCH₂CH₂O- is found to be the stable reaction intermediate, which starts to appear at ∼190 K. At low coverages, this intermediate decomposes into H₂ and CO. Additional C₂H₄ (219 K) is generated at higher exposures. On Ni(111) at 200 K, ClCH₂CH₂OH mainly dissociates to form ClCH₂CH₂O- and -CH₂CH₂O- at lower exposures, with H₂ and CO as the final products, while ClCH₂CH₂O- becomes predominant at higher exposures and is responsible for the extra C₂H₄ channel of 218 K. C₂H₄ is also generated at 161 and 174 K as the exposure is increased to render multilayer adsorption. Due to the competition in the scission of the carbon–halogen and carbon–hydrogen bonds, ClCH₂CH₂OH has better reactivity toward C₂H₄ formation than FCH₂CH₂OH. No -CH₂CH₂OH is found in the decomposition of FCH₂CH₂OH and ClCH₂CH₂OH on Ni(111), which is the intermediate in the reaction of ICH₂CH₂OH on Ni(100) and Pd(111). The presence of preadsorbed oxygen can enhance the ethylene formation at low coverages of FCH₂CH₂OH and ClCH₂CH₂OH. At higher coverages, additional acetaldehyde is formed in the reaction of FCH₂CH₂OH, in contrast to the ethylene oxide from ClCH₂CH₂OH