AREA DETERMINATION IN FRACTAL SURFACES OF PT AND PT-RU ELECTRODES

A fractal approach using corrugation data to calculate surface area is offered as an alternative to gas adsorption technique. The surfaces o f mechanically polished polycrystals of pure Pt and Pt-Ru(40%) alloy w ere examined using scanning tunneling microscopy. Over a range of 0.01 -10 mu m lengths, three fractal dimensions were identified. Measuremen ts made at randomly selected locations separated by distances>0.1 mm s howed the existence of the three domains everywhere. However, in each domain, the fractal dimensions, D, varied from one location to another , suggesting a stochastic distribution of D. The stochastic data was u sed to calculate the surface area, In the pure Pt case, the area calcu lated on this basis correlated well with the area measured by the anod ic stripping of adsorbed hydrogen. The usefulness of the fractal appro ach to area calculation in the Pt-Ru alloy, where the hydrogen absorpt ion technique cannot be used, is demonstrated. (C) 1997 Elsevier Scien ce B.V.