Site-specific catalytic activity of model platinum surfaces in different electrolytic environments as monitored by the CO oxidation reaction.

Stepped Pt surfaces having different width (1 1 1) terraces interrupted by (1 1 0) or (1 0 0) monoatomic steps were employed to evaluate the catalytic activity toward CO oxidation at Pt specific sites in HClO 4 , H 2 SO 4 , and H 3 PO 4 solutions, as well as in phosphate buffer and alkaline solution. The catalytic activity at the (1 1 1) terraces was sensitive to the nature of the anions derived from the electrolyte dissociation, while no effect on activity was detected at the monoatomic steps. A change in solution pH, passing from acid to alkaline solutions, had contrasting effects on catalytic activity at the (1 1 1) terraces and the step sites, with the catalytic activity of the (1 1 1) terraces improving, while activity at the step sites deteriorated. During the CO adlayer oxidation, the release of surface sites occurred preferentially from the (1 1 1) terraces of the Pt(s) − [( n − 1)(1 1 1) × (1 1 0)] surfaces, while from Pt(s) − [( n )(1 1 1) × (1 0 0)] surfaces, (1 1 1) terrace and (1 0 0) step sites were released simultaneously. [ABSTRACT FROM AUTHOR]