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pH dependent effect of stirring on the electrode potentials of the metal oxide single crystal electrodes

During the potential measurements of the metal oxide single crystal electrodes [1, 2] certain influence of stirring of the solution on the measured potentials was observed. The effect of stirring on the (glass) electrode potential was known from previous research [3–5]. However, theoretical explanation of this effect never converged into the wide accepted model. The general lack of interest for this phenomena is mostly due to the fact that the magnitude of this effect is negligible in daily pH measurements. However, in some cases, when measuring the potentials on SCrE, the measured signal magnitude might be low enough (i.e. E < 5 mV) to make those stirring effects the factor which shouldn't be neglected. For the purposes of more precise SCrE potential measurements, necessary for the investigation of the mechanisms contributing to the electrode potentials, the effect of stirring was investigated as a function of pH. It was observed that not only the magnitude of the stirring influence varies with pH, but the direction of those changes also reverses at certain pH. The plot of ΔEstirr. vs. pH is linear, with variable slopes dependent on the SCrE material used. The potential response of the SCrE to stirring was measured. The signal shapes that were obtained by switching stirring on and off indicate involvement of more than one simultaneous and possibly independent contributing mechanisms.

surface potential, stirring, electrical interfacial layer, metal oxide, ion distribution

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