Preparation and Electrochemical Properties of Polyaniline Nanostructures Using Vertically Aligned Mesochannels as Confinement

Abstract

One-dimensional conducting polymer nanowire arrays have shown promising potential in applications of electrochemical supercapacitors, sensors, and more. Herein, vertically aligned mesoporous silica films (VMSF) with hexagonally packed mesochannels were generated on indium-tin oxide (ITO) electrodes by an electrochemically-assisted self-assembly (EASA) method. The prepared VMSF/ITO electrode was then exploited as a hard template for electrochemical growth of well-aligned polyaniline (PANI) nanofilaments within silica mesochannels, eventually forming a PANI/VMSF/ITO composite electrode. The electrochemical conditions of the PANI growth through the mesochannnels were investigated in detail, and the electrochemical capacitance was also tested. It is shown that the resulting nanofilaments separated through silica walls exhibit significantly improved electrochemical performance, including better electrochemical reversibility and high specific capacitance (3.00 mF/cm 2 at 20 μA/cm 2 ), which is increased by about 152 % in comparison to PANI directly on an ITO (PANI/ ITO) substrate. Such an improved electrochemical performance is mainly contributed to by enhanced charge transfer efficiency and improved electrochemical reaction kinetics resulting from the well-aligned PANI nanostructure.

Electrogeneration of non-electroactive and non-conducting materials: a counterintuitive concept for the functionalization and nanostructuration of electrode surfaces

“…Interestingly, the anodic-to-cathodic peak-to-peak separation for the individual nanofilaments separated from each other by the silica walls was close to 60 mV, a much lower value than that observed for bulk PANI films (ca. 120-130 mV), suggesting a more reversible electrochemical behavior in the former case [352] and higher specific capacitance [365]. Unfortunately, such PANI nanofilaments are not durably attached to the underlying electrode support (ITO in this case) and are lost in solution when dissolving the silica membrane [366].…”

“…Well-aligned 1D-polyaniline (PANI) nanofilaments as nanoarrays generated by electropolymerization through silica nanochannels membrane (Figure 17D) exhibit improved electrochemical performance compared to bulk PANI deposits [353,365]. They are promising for application as electrochemical supercapacitors, reaching high specific capacitance (3.00 mF•cm −2 at 20 µA•cm −2 , i.e., an increase by 152% in comparison to PANI directly deposited on ITO substrate) [365].…”

“…Well-aligned 1D-polyaniline (PANI) nanofilaments as nanoarrays generated by electropolymerization through silica nanochannels membrane (Figure 17D) exhibit improved electrochemical performance compared to bulk PANI deposits [353,365]. They are promising for application as electrochemical supercapacitors, reaching high specific capacitance (3.00 mF•cm −2 at 20 µA•cm −2 , i.e., an increase by 152% in comparison to PANI directly deposited on ITO substrate) [365]. Similar observations can be made with polypyrrole (PPy) nanowire electrodeposits, for which specific capacitance values 60 times higher than bulk PPy was reported [363], but the nanowires diameter was around 30 nm suggesting that they probably grew also out of the mesoporous membrane.…”