Auger electron spectroscopy (AES) and high-resolution electron energy loss spectroscopy (HREELS) showed that hydrogen reduction at 700 °K of a 120-Å nickel film deposited on TiO2 results in the segregation of TiOx (x close to 1) onto the nickel surface. Titanium oxide appears to diffuse rapidly through nickel. Room-temperature CO uptake was found to decrease with increasing surface titanium oxide concentration. HREELS showed that the concentration of bridge-bonded CO relative to on-top CO after room-temperature CO exposure decreases with increasing titanium oxide coverage on nickel. A site giving rise to a CO stretching frequency of 1850 cm-1 was found to survive after extended reduction. This was attributed to a site near the surface titanium oxide on nickel. The present study suggests that both physical coverage of the nickel surface by TiOx and the chemical interaction between nickel and TiOx on the surface are involved in SMSI.
ASJC Scopus subject areas
- Process Chemistry and Technology