ADSORPTION OF CARBON MONOXIDE ON Ni/Ti AND Ni/TiO2 SURFACES PREPARED IN SITU IN THE ELECTRON SPECTROMETER: A COMBINED UPS-XPS STUDY

Adsorption of CO on a clean Ti surface is partly associative at 80 K with a 1 pi-4 sigma separation of 4.2 eV, becoming dissociative at 130 K. On Ni- covered Ti surfaces, however, associative adsorption (4 sigma- 1 pi, 3.3 eV) occurs at 80 K and partial dissociation, around 200 K. TiO2 is reduced more effectively on annealing, when it is covered with Ni. On the surfaces of Ni deposited on TiO2, there is only dissociative adsorption, unlike on Ni/Al2O3 and Ni/TiO2 (non-annealed) surfaces.