ELECTROCHEMICALLY INDUCED SURFACE CHANGES ON MICROSTRUCTURED PT FILMSON A SOLID YSZ ELECTROLYTE

Thin (500 Angstrom) microstructured Pt films on single crystalline ytt rium stabilized zirconia (YSZ) prepared by photolithography have been used to study the processes at the interface between the solid electro lyte and the Pt film when electrical potentials are applied. The exper iments are performed under UHV conditions with a standard three-electr ode set-up employing photoemission electron microscopy (PEEM) as spati ally resolving method. Upon electrochemical ''pumping'' of oxygen by a pplying a positive electric potential to the Pt film we observe in PEE M a darkening of the Pt film reflecting a work function (WF) increase; a negative potential leads to a WF decrease. No time-dependent spatia l concentration profiles which would have been indicative of the slow diffusional spreading of a spillover species were observed.