Suppression of formation of ethylidyne on Pt(111) by reversibly adsorbed di-σ-bonded ethylene studied by in situ IRAS

Abstract The suppression of ethylidyne formation on Pt(111) by reversible adsorption of di-σ-bonded ethylene in the presence of 1.3×10 2  Pa of ethylene was observed using infrared reflection absorption spectroscopy (IRAS). Di-σ-bonded ethylene was converted to ethylidyne at 260–300 K in 1.3×10 2  Pa of ethylene, while it was converted at 240–260 K in vacuum. The vacant sites adjacent to di-σ-bonded ethylene are regarded as being necessary for ethylidyne formation, which were occupied by di-σ-bonded ethylene equilibrated with gaseous ethylene. The reversible adsorption of di-σ-bonded ethylene was notified by an IRAS peak at 2906 cm −1 even at 300 K, which was confirmed by the substitution of isotopically labeled ethylene at 200 K.