Adsorption and Reaction Pathways of 1H-Pyrazole on Cu(100) and O/Cu(100)

Temperature-programmed reaction/desorption (TPR/D), reflection–absorption infrared spectroscopy (RAIRS), X-ray photoelectron spectroscopy (XPS), and near-edge X-ray absorption fine structure (NEXAFS) have been employed, with the aid of density functional theory calculations, to investigate the adsorption and reaction mechanisms of 1H-pyrazole on Cu(100) and oxygen-precovered Cu(100) (O/Cu(100)). On Cu(100), the adsorbed 1H-pyrazole molecules interact with each other through hydrogen bonding, exhibiting broad infrared absorptions between ∼2750 and ∼3300 cm–1, but without the N–H stretching peak detected. Near a monolayer coverage, heating the surface to ∼200 K induces a change in the adsorption layer structure and generates upright or near upright 1H-pyrazole molecules attaching to the surface through the imine nitrogens. The 1H-pyrazole undergoes N–H bond cleavage first to evolve H2 (∼230 K) and leaves pyrazolate on the surface. This intermediate is proposed to be adsorbed perpendicularly via the two nitr...