Symmetric ultracapacitors have been fabricated considering nanometric 3-layered films
made of alternated layers of poly(3,4-ethylenedioxythiophene) (external and internal layers)
and polypyrrole (intermediate layer) deposited on steel uncoated and coated with
octanethiol self-assembled monolayer. The highest electrochemical and capacitance
parameters (i.e. electroactivity, doping level, stored charge, specific capacitance, Coulomb
efficiency, energy density and power density) correspond to the ultracapacitor derived
from the assembly of 3-layered films deposited on pre-treated steel. Thus, the interface
separating the octanethiol monolayer and the most internal layer of the 3-layered film produces
a very favorable interaction, which promotes important electrochemical benefits
similar to those found for the interfaces in conventional multilayered films. Moreover,
the pre-treatment of the steel electrode enhances the roughness and porosity of the film
deposited on it, transmitting this effect layer-by-layer. Structural and morphological characteristics,
which have been characterized using scanning electron microscopy and atomic
force microscopy, have been related with the electrochemical and capacitance properties of
the ultracapacitors.