Adsorption and Reaction Pathways of 1 H-1,2,3-Triazole on Cu(100) and O/Cu(100)

The adsorption and reactions of 1H-1,2,3-triazole on Cu(100) and oxygen-precovered Cu(100) [O/Cu(100)] have been investigated using the combinative techniques of temperature-programmed reaction/desorption, X-ray photoelectron spectroscopy, reflection-absorption infrared spectroscopy, and near-edge X-ray absorption fine structure in addition to density functional theory calculations. Although the 1,2,3-triazole molecules may have 2H-tautomeric form, it is found that the 1H-form is predominantly adsorbed on Cu(100) at 120 K. The adsorbed 1H-1,2,3-triazole molecules interact with each other via hydrogen bonding. The triazole molecules on Cu(100) undergo N-H bond scission first to form nearly perpendicular 1,2,3-triazolate on the surface. H₂ evolves below 350 K through two different mechanisms depending on the coverage. The triazolate on Cu(100) further decomposes to form H₂, HCN, N₂, and CH₃CN at ∼550 K. The latter three products are generated by the triazole ring opening with preferential bond dissociation steps. On O/Cu(100), the triazole molecules deprotonate first by N-H breakage, forming H₂O at ∼200 K but without H₂ desorption below 350 K. The 1,2,3-triazolate reacts to generate H₂, N₂, H₂O, CO, and CO₂ at a lower temperature of ∼465 K in the presence of surface oxygen. C-C-N and/or C=N containing intermediates are likely to be formed on the surface from the triazole ring rupture and are suggested to be responsible for the formation of 1H-azirine or vinylideneamine.