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Abstract

A smooth Pt(111) single-crystal surface was locally roughened by pulsed laser irradiation. Single laser pulses of intensity less than 1 J/cm² already created an observable amount of surface defects, although the induced temperature increase was below the melting temperature of Pt. After laser irradiation the Pt(111) sample displayed an additional high temperature CO desorption peak which increases with the number of laser shots and disappears upon annealing the sample at 1000 K. The (reversible) creation of defect concentration was verified by an analysis of thermal desorption (TD) spectra of CO, which the crystal was exposed to at room temperature. A higher catalytic activity of the defect-enriched Pt surface for CO oxidation was observed if the same reaction parameters were applied. This can be explained in terms of an enhanced sticking probability for oxygen at defect sites, which shifts the CO poisoning transition to higher ρ_CO values. By increasing the crystal temperature linearly during reaction at fixed pressures, the transition from low to high reactivity was studied.