Time-Dependent Modeling of Salt-Contaminated Acid-Base Diodes

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.