Electrochemical bubble generation via hydrazine oxidation for the in situ control of an electrodeposited conducting polymer micro/-nanostructure

Abstract

Herein, a simple, in situ, on step and highly repeatable electrochemical method that allows controlling the nanostructure of electrodeposited polymer films is reported. As an example, the tuning of the electrodeposited polypyrrole nanostructures using inert gas bubbles as the template at the electrode surface generated by the electrochemical oxidation of hydrazine is shown. The hydrazine discharge occurs at a lower potential regarding the beginning of pyrrole electropolymerization process, which allows the modulation of the density and size of the bubbles on the surface electrode controlling electrochemical parameters (applied potential, concentration, time, etc.). Subsequently, the applied potential is moved to where the pyrrole polymerization begins, which induces the material discharges around the bubble template producing polypyrrole hollow structures with definite patterns on the electrode surface. This methodology is proposed as a simple model for the electrodeposition with the morphological control of a wide range of conductive polymers.

Fig. 1. SEM images of the surface of the PPy film on the ITO electrode, which was electrodeposited from different N₂H₄ concentrations (rows: 0, 25, 50 and 100 ppm) and at different waiting times (columns: 0, 15, 30, 60 and 180 s) at 0.30 V. The pyrrole monomer concentration was fixed at 10 mM in the DCE solution containing 0.1 M TBAPF₆ as the electrolyte. Scale bar: 2 μm.

Fig. 2. Variation of the inner tube diameter and tube density at different N₂H₄ concentrations as a function of the paused time at 0.30 V. The pyrrole monomer concentration was fixed at 10 mM in the DCE solution containing 0.1 M TBAPF₆. The orange and green arrows indicate where the tubular structures are isolated or collapsed, respectively.

Fig. 3. Magnification of the SEM images of the surface of the PPy film on the ITO electrode shown in Fig. 1 where cluster formation is observed. Scale bar: 1 μm.