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IRAS Study Of Formic Acid Decomposition On NiO(111)Ni(111) Surface: Comparison Of Vacuum And Catalytic Conditions
Published 1996 · Chemistry
Decomposition of formic acid on an NiO(111) surface grown on Ni(111) under vacuum and catalytic conditions was investigated by infrared reflection absorption spectroscopy. It was found that adsorbed formic acid under ultra-high vacuum conditions formed bidentate formate which was tilted along the molecular plane. Formic acid decomposed catalytically over the NiO(111) surface at 423 K and 10−3 Pa of formic acid with small activation energies of 22 and 16 kJ mol−1 for dehydrogenation and dehydration, respectively. Both monodentate and bidentate formate were observed on the surface under the catalytic condition. The monodentate formate was identified as an intermediate of decomposition from the similarity between the pressure dependence of the coverage and that of the decomposition rate estimated from the partial pressures of the products. The bidentate species observed under the catalytic condition was oriented normal to the surface in contrast to the titled orientation in vacuum, indicating structural change of the surface.