Electric Field Distribution in Bipolar Electrochemical Cells: Effects on the Wirefree Electrodeposition of Conducting Polymer Films

Wirefree, or bipolar electrochemistry, is advancing key fields, including (nano)materials, human health, and energy. Central to these applications is an understanding of the potential distribution induced in the bipolar electrode, BPE. Here, the impact of the electric field distribution is reported for the wirefree deposition of the conducting polymer, poly(3,4-ethylenedioxythiophene), PEDOT, in the absence of deliberately added electrolytes. PEDOT films with a gradient thickness are deposited, and the films formed at 10 V cm^-1 for 20 min have an average film thickness of 350 nm. Significantly, the quantity of the polymer deposited increases proportionally to the deposition time up to approximately 20 min, suggesting that the presence of a thin PEDOT film does not change the interfacial potential distribution or driving force for heterogeneous electron transfer. For electric field strengths ≥5 V cm^-1, PEDOT is deposited on regions of the BPE where the voltage is predicted to be insufficient to drive electropolymerization. This result demonstrates that local intensification of the field, e.g., at edges, and migration of the cationic radicals can significantly affect the electrodeposition profile. These results provide an enhanced understanding of the potential profiles for applications from multianalyte detection devices to wirefree electroceuticals.