Partially selective semiconductor redox electrodes

Abstract

Redox electrodes made of passivated metals of the subgroups IV to VI of the periodic system with a surface coating of n-conducting metal oxides, generated by oxidizing agents or anodic oxidation, are well suited for measuring the concentration of oxidizing agents. Neither oxygen nor reducing agents affect the measurements. There is a correlation between the mean conductivity of the passive layer and its selectivity. The aged n-conducting passive layers permit reproducible potential settings, and the occurring changes in potential are greater than what is to be expected according to the Nernst equation. The potentiometric measuring of nitrosyl ions and chlorine is used as an example to demonstrate the selectivity of these electrodes.

Study of the structure of passivated vanadium-titanium alloys and their semiconductor properties

“…These results are in accordance with electrochemical investigations [12] and also with the consideration that in the system n-type semiconductor/redox electrolyte electron transfer proceeds mostly via the conduction band (energy level of the redox system overlaps with the conduction band). According to Habermann [5] there is a correlation between the mean conductivity of the passive layer and its selectivity in electrochemical systems. In the example described the conductivity decreases as the amount of titanium in the alloy is reduced.…”

“…Today it is beyond doubt that passive oxide layers on metals usually have semiconductor properties [4]. It is also assumed that this favorable electrochemical behavior of the oxide layers is mainly a consequence of electronic and ionic defects [1,5].…”