Reaction of sulfur dioxide with Ni(1 0 0) and Ni(1 0 0)-p(2 × 2)-O

XPS, TPD, LEED and STM have been used to probe the interaction between sulfur dioxide and the Ni(1 0 0) and Ni(1 0 0)-p(2 × 2)-O surfaces. On Ni(1 0 0) at 300 K SO2 disproportionates according to 2SO2 → S(a) + SO3(a) + O(a). Sulfur and sulfite occupy sites in a p(2 × 2) arrangement, while oxygen adsorbs into c(2 × 2) domains amid Ni chains of (n√2 × 2√2)R45°/(2√2 × n√2)R45° (n = 7-12) periodicity that are presumed to be due to segregation of oxygen to the subsurface. On Ni(1 0 0)-p(2 × 2)-O at 300 K SO2(a) reacts with O(a) to form SO3(a). Sulfite adsorbs into p(2 × 2) islands encompassed by c(2 × 2)-O. TPD measurements with 18O are suggestive of a monodentate sulfite binding configuration.