Abstract:
Adsorption of nitrogen on Ni/TiO{sub 2}, Ni/Al{sub 2}O{sub 3}, Ni/Al, Ni-Ti alloy, TiO{sub 2}, and other surfaces prepared in situ in an electron spectrometer has been investigated by X-ray and UV photoelectron spectroscopy to understand the nature of the strong metal-support interaction (SMSI) state in the annealed Ni/TiO{sub 2} catalyst system. The annealed Ni/TiO{sub 2} surface has a considerable proportion of Ti{sup 3+} and exhibits dissociative adsorption of N{sub 2} along with weak molecular chemisorption at 80 K just as a Ni-Ti alloy surface. This is in contrast with the nonannealed Ni/TiO{sub 2} surface where there is only molecular chemisorption at 80 K similar to the Ni/Al{sub 2}O{sub 3} surface. The adsorption behavior of the annealed Ni/TiO{sub 2} surface is also different from that of TiO{sub 2} (showing only physisorption), TiO{sub x} (reduced surface showing physisorption and dissociation) or Ni/TiO{sub x} (dissociation and stronger chemisorption as on Ni/TiO{sub 2}). It is suggested that the annealed Ni/TiO{sub 2} surface may correspond to the SMSI state.
