Until now, polyvinyl alcohol (PVA) gel cylinders have been used in electrolyte diodes as a connecting element between the acidic and alkaline reservoirs. In this paper, a new connecting element is reported: a breath figure templated polyvinyl butyral (PVB) membrane prepared with dip-coating from a dichloromethane solution of the polymer in a humid atmosphere. The procedure gives a 1.5-2 μm thick membrane with a hexagonal pattern, the average characteristic length of which is 1 μm. After an acidic etching, it was found to be a good connecting element. The voltage-current characteristics and dynamic properties of PVA and PVB were measured and compared. The PVB membrane has a faster response to voltage changes than the PVA gel, but in both cases, there was a slow drift in the current that prevented it from reaching a steady state. Reproducible characteristics can be obtained, however, after the current reaches a well-defined quasi-steady state.

The paper describes the transient behavior and modeling of the salt contaminated acid-base diode. As an example, a 0.1 M KOH-0.1 M HCl diode (used in previous investigations), where the alkaline and acidic reservoirs are connected by a hydrogel cylinder is studied. First the traditional positive salt effect and the fairly new phenomenon called negative salt effect are discussed for stationary state. In the case of positive salt effect some salt is added to the alkaline reservoir of a reverse biased electrolyte diode and as a result, close to the critical concentration of the added salt, the current increases sharply. The negative salt effect appears as a suppression of the positive one (both sides of the diode are contaminated). Afterward the time-dependent positive and negative salt effect are discussed as a step response to the salt contamination. An application of the diode would be the sensitive detection of nonhydrogen cations in an acidic medium (e.g., in ion chromatography) based on the negative salt effect, thus our first results of suitability are studied and reported as impulse response of the diode.

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An application of the so-called acid-base diode would be the sensitive detection of nonhydrogen cations in an acidic medium based on salt-effects. For diode purposes different connecting elements between the acidic and aqueous reservoirs of the diode were developed, namely a polyvinyl alcohol (PVA) hydrogel cylinder, and a polyvinyl butyral (PVB) membrane. During the measurement of the voltage – current characteristic (VCC) of the diode, it was found, that in the case of PVA gel cylinder an overshoot (a local maximum followed by a local minimum) appeared in the time vs. current curve, while the diode was switched between modes (open or closed), that is the direction of the applied voltage was reversed. The overshoot did not appear in PVB membrane.The existence of overshoots was studied by numerical simulations. The time response of the diode with different hypothetic connecting elements was investigated, when the diode was switched between modes via changing the polarity of applied voltage. We found that larger diffusion coefficients of hydrogen and hydroxide ions explain the appearance of overshoots. By examining the concentration and potential profiles a qualitative explanation of this phenomenon was given.

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