| Abstract
| - An electrochemical quartz crystal impedance system(EQCIS) was used to investigate depletion layer effectson equivalent circuit parameters of piezoelectric quartzcrystal resonance in electrochemical processes of CoSO4aqueous solutions containing 0.4 mol/L ethylenediamine+ 0.5 mol/L Na2SO4, 0.2 mol/L 1,10-phenanthroline +0.5 mol/L Na2SO4 and K3Fe(CN)6, or K4Fe(CN)6 aqueoussolutions containing 1.0 mol/L KCl in potential cyclingexperiments, respectively. The impedance data wereanalyzed according to Martin's model. For the former twosystems, motional resistance R1, series resonant frequency fs, and motional inductance L1 changed reversiblywith potential, and the observed values of ΔR1, ΔL1, andΔfs roughly satisfied equations reflecting liquid loadingeffects, suggesting that changes in these parameters mightbe mainly governed by local variations in solution densityand viscosity near the electrode surface. For the latter twosystems, reversible changes in R1 with potential coincidedwell with the simulated results from variations in solutiondensity and viscosity near the electrode surface; however,besides reversible changes of ΔL1 and Δfs with potential,rising drifts of fs and decreasing drifts of L1 were foundat oxidation potentials. The drifts of fs and L1 observedare believed to result from mass changes of the goldelectrode, and cyanide and chloride corrosion of the goldelectrode at oxidation potentials may play an importantrole for the drifting phenomena. It is concluded thatquantitative analyses of ΔR1, ΔL1, and Δfs obtained fromthe EQCIS provide the possibility for differentiating thenet depletion layer effect with the change in electrodemass, and the ΔR1 response may be well used forevaluating local changes in liquid loading inside thedepletion layer compared with responses of Δfs and ΔL1.
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