The reduction of disordered and ordered tin oxide monolayers and multilayers on Pt(111) by H2 was studied in situ by ambient pressure X-ray photoelectron spectroscopy. The disordered tin oxide monolayer was highly reactive and reduced by 5.5 × 10-7 Torr H2 at 295 K. However, the ordered monolayer was much less reactive, and nearly inert even in 2.2 Torr H2 at 295 K. Reduction of the tin oxide monolayer occurred only when the sample temperature increased to above 600 K in 5.5 × 10-7 Torr H2 or when the sample temperature was 450 K in 2.2 Torr H2. Disordered and ordered multilayers were found to be much less reactive by comparison to the disordered monolayer film. The reduction activity of these ordered and disordered Sn oxide films varied dramatically (by a factor of 107), demonstrating the structural flexibility of Sn oxides and the key interplay of structure and reactivity.
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