Adsorption and reaction of sulfur dioxide with Cu(110) and Cu(110)-p(2×1)-O

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Abstract
On Cu(110)-p(2×1)-O at 300 K SO2(g) reacts stoichiometrically with O(a) to form a surface covered with both c(4×2)-SO3 and p(2×2)-SO3 structures. With heating SO2(g) evolves from the surface in distinct reaction-limited states at 384 K, 425 K, and 470 K, and the surface reverts to its initially oxidized state. On Cu(110), SO2(g) adsorbs molecularly below 300 K; upon annealing to 300 K, the sulfur dioxide disproportionates according to 3SO2(a)→S(a)+2SO3(a) with concomitant desorption of excess SO2(a). The surface formed in this manner exhibits large c(2×2)-S domains which encompass scattered c(4×2)-SO3 and p(2×2)-SO3 structures in a 1:2 coverage ratio. After being annealed to 400 K, the surface exhibits large p(2×2)-SO3 domains surrounding smaller c(4×2)-SO3 and c(2×2)-S islands. Continued heating past 400 K results in decomposition of sulfite according to SO3(a)→SO2(g)+O(a), evolving sulfur dioxide at 470 K and leaving the surface covered with atomic sulfur and oxygen. Real-time STM images show the mobility of oxygen at island boundaries and the mobility of sulfite amid the p(2×1)-O structures. STM measurements suggest that the sulfite occupy four-fold hollow sites.