ELECTROCHEMICAL PROMOTION OF OXYGEN-ATOM BACK-SPILLOVER FROM YTTRIA-STABILIZED ZIRCONIA ONTO A POROUS PLATINUM-ELECTRODE - DETECTION OF SERS SIGNALS

During anodic current operation (I = 0.6 mu A) at 315 degrees C of a O -2, Pt/ZrO2 (8 mol % Y2O3/Ag, O-2 galvanic cell, we have detected Rama n scattered photons from the Pt electrode. The corresponding bands hav e been assigned to the transient formation of Pt-O bonds with an unusu ally low vibrational frequency. The temporal evolution of the signals, at a constant value of current intensity, temperature, and oxygen flo w conditions, has been related to the migration (spillover) of oxygen species from the solid electrolyte-metal-gaseous oxygen three-phase bo undary zone onto the porous Pt electrode. These observation give direc t information about oxygen atom motion which results from the O2- ions pumping toward the working electrode under conditions in which the no n-Faradaic electrochemical modification of catalytic activity has been observed.