Electrochemically Produced Bubbles May Induce Negative Frequency Shift

4 Electrochemically Produced Bubbles May Induce Negative Frequency Shift 

The standard picture of slip predicts an increase of frequency upon bubble formation. This has repeatedly been observed. Tsionski et al. went through a particularly careful study, which yielded a negative result these authors did not see a frequency shift under conditions where they expected the presence of nanobubbles on the basis of their knowledge of the electrochemistry going on in the cell.55 

In the authors laboratory a negative frequency shift upon gas was also observed. This effect is most pronounced when the bubbles are small. A set of experimental results is shown in Fig. 8.4. This data was acquired with an electrochemical QCM (EQCM ) in water. In EQCM, the front electrode of the resonator at the same 

At t = 10 minutes, the voltage at the working electrode was lowered by —1 volt, which induced hydrogen evolution. The voltage was shut off after 0.5 seconds. Had the voltage been applied for a longer time, macroscopic bubbles would have evolved. Due to the 

we put this argument into a more quantitative form. We argue that the effect of surface tension can be captured by assigning stiffness equal to the Laplace pressure to the interior of the bubble. Consider the deformed bubble depicted in Fig. 8.5. The curvature of the interface has decreased on the left-hand side, while it has increased on the right. In the limit of small amplitude, shear transforms a spherical bubble into an ellipsoid. 

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