U.H.V. Electrochemical transfer studies of modified platinum single crystal surfaces : Models for fuel cell catalysis

Davies, Jonathan Conrad (1999) U.H.V. Electrochemical transfer studies of modified platinum single crystal surfaces : Models for fuel cell catalysis. University of Southampton, Doctoral Thesis.

Abstract

Adsorbed and incorporated ruthenium on Pt(110) has been probed using the techniques of LEISS, LEED and XPS. Well characterised alloy surfaces have been prepared by annealing in the temperature range 400-1100K and the temperature programmed desorption of CO investigated. Second layer ruthenium is shown to have a major effect on the adsorption characteristics of CO. The catalytic activity of these surfaces towards the electro-oxidation of CO has been determined using cyclic voltammetry. The reversible hydrogen adsorption peaks are perturbed by subsurface ruthenium, however, promotion of the electro-oxidation of CO, as evidenced by a downwards potential shift, occurs solely due to ruthenium incorporated into the top atomic layer.

The adsorption of ruthenium on Pt(111) has been investigated by LEISS, XPS and LEED. At room temperature clusters of ruthenium are obtained. On annealing competition occurs between the processes of spreading of these clusters and incorporation of ruthenium into the Pt(111) surface.

Two Clavilier bead crystals have been prepared of the Pt(111) and Pt(533) surfaces. Promotion of the electro-oxidation of CO by ruthenium spontaneously deposited onto these surfaces from a RuCl₃ solution, before and after reduction of the surface ruthenium species, has been demonstrated. A particularly sharp oxidation peak at 0.53 V is observed on the Pt(533) - Ru system after exposure to hydrogen, attributed to the formation of an ideal "alloy" ensemble at the step.

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