Chemisorption of sulfur dioxide on tungsten and platinum surfaces

The chemisorption of SO2 on a W and a Pt surface has been investigated by flash desorption mass spectrometry (FDMS) and AES. AES data indicate that the chemisorbed sulfur dioxide molecules oxidized the W surface, and produced a stable tungsten oxide during the heating (up to 1400 K) process. FDMS data indicate that the decomposition of SO2 yielded elemental and molecular sulfur during the desorption process. FDMS data show that SO2 exists in four binding states (α1, α2, α3 and α4) on a clean Pt surface and in three binding states (α5, α6 and α7) on an oxidized Pt surface. In addition, the coadsorption of SO2 and O2 was carried out on a Pt surface. The coadsorption process can produce SO3 which exists in two different binding states on a Pt surface. The data indicate that the oxidation of SO2 to form SO3 on a Pt surface occurs by means of a Langmuir–Hinshelwood mechanism.