Interactions of SO2 with sodium deposited on silica

The interaction of SO2 with single-crystal surfaces of SiO2 at temperatures of 298, 473, and 673 K, which were covered by various amounts of sodium, was studied using X-ray photoelectron spectroscopy. The sodium was deposited on SiO2 in the Na+ state, as indicated by an Auger parameter study. Scanning electron microscopy showed dramatic changes in surface morphology on SiO2 after deposition of sodium. The amount of adsorbed SO2 increased with increasing sodium deposition at both 298 and 473 K. This adsorbed sulfur was identified as sulfite. Sticking probability calculations indicated that the reaction was a first-order or direct one-site adsorption. The initial sticking probability increased with increasing sodium coverage. When the SO2 reaction was carried out at 473 K, both the amount of adsorbed SO2 and the initial sticking probability were higher than they were at 298 K. No reaction was observed at 673 K.