In situ microweighing at the junction metal/electrolyte

Abstract

Abstract We report on in situ measurements of frequency shifts and charge fluxes registered simultaneously with the Electrochemical Quartz Microbalance (EQMB) on 5 MHz, 6 MHz and 10 MHz crystals, oscillating in a liquid environment. The investigations on gold electrodes reveal an influence of pH on the interfacial processes forming oxidic overlayers. This result is in agreement with a recent XPS investigation on emersed samples. It is further demonstrated, that in contrast to a single potential excursion the metallic gold surface becomes rough upon multiple potential excursions. This becomes evident from a frequency gap, that persists upon reduction. Anodic and cathodic processes on platinum electrodes lead to strong frequency changes, which are not related to weight changes. In agreement with an IR study performed recently on emersed Platinum electrodes, We attribute these frequency changes upon cycling to a transition from the hydrophilic to the hydrophobic surface state and vice versa.