Application of a self-powered bipolar electrode system for silver ion release controlled by a chemical stimulus

Abstract Applicability of a self-powered cascade bipolar electrode system for driving chemical charge transfer reactions (which under typical conditions do not occur spontaneously) was tested. As a proof of concept, oxidation of silver to silver ions was studied because the controlled release of small amounts of silver ions is of practical significance, e.g., due to their antibacterial activity. Since bacterial infection results in local acidification, effective bacteria killing by silver ions requires “stimuli-pH responsive” silver ions releasing arrangements. The applied cascade system consists of two bipolar electrodes (circuits) arranged in closed mode. One of the circuits, the “driving” one, is characterized by a high potential difference between opposite ends of the electrode (zinc wire connected with platinum electrode in the presence of hydrogen ions). Therefore, this bipolar electrode can trigger the silver oxidation process at the second bipolar electrode (silver/silver chloride electrode connected with silver wire). Cascade bipolar electrode architecture opens the possibility of tailored coupling chemical processes without need of electrochemical instrumentation. In the studied simple system, the process of silver oxidation can be effectively stimulated and controlled by the concentration of hydrogen ions contacting the platinum electrode, as a model of “stimuli-pH responsive” system, where lower pH actuates a higher rate of silver ion release. Electrochemical experiments were supplemented by quantification of silver and zinc released (ICP MS, UV/Vis). Basing on these results, some more general predictions concerning charge transfer reactions control and their sensitivity to external conditions for bipolar electrode systems were proposed.