SIMULTANEOUS NORMALIZED OPTICAL REFLECTIVITY AND MICROGRAVIMETRIC MEASUREMENTS AT ELECTRODE-ELECTROLYTE INTERFACES - THE ADSORPTION OF BROMIDE ON GOLD IN AQUEOUS-MEDIA

A system is herein described for the simultaneous acquisition of in si tu microgravimetric (QCM) and UV-visible reflectance data (Delta R/R) of metal film electrodes sputtered on the surface of optically polishe d quartz crystals. This dual-technique approach makes it possible to e stablish correlations between the changes in weight and relative refle ctivities associated with the adsorption of ions (and other species) o n the electrode surface as a function of the applied potential without uncertainties derived from electrode surface preparation. Simultaneou s in situ QCM-Delta R/R measurements for the adsorption of bromide on gold from aqueous electrolytes yielded results in excellent agreement with those reported by other authors for each independent technique. I n particular, plots of the change in the resonant frequency of the QCM vs Delta R/R were found to be linear in the potential region in which bromide adsorption is expected to occur for concentrations of bromide spanning more than 2 orders of magnitude.