Facile fabrication of polyaniline films with hierarchical porous networks for enhanced electrochemical activity

This paper describes a facile method for fabricating polyaniline (PANI) films with well-defined three-dimensional (3D) porous networks and improved electrochemical activity. The PANI hydrogel pastes with different compositions are directly cast into thin films by the doctor blade technique. After a dehydration step, the conductivity of the PANI drastically increases, while the porous structure with hierarchical macro- and meso-porosity is formed in the PANI film. The electrical conductivity tends to increase with the thickness of the porous PANI film until it fails to form a mechanically stable film not exhibiting cracking problems. We found that the amount of the initiator, the aniline monomer, and the crosslinker significantly affect not only the micro-morphology of PANI films, but also their electrical and electrochemical characteristics. Importantly, when the amounts of the crosslinker and the initiator increase, the polymer film forms with a dense internal morphology with smaller pores. Based on the engineered synthesis composition, we demonstrate a supercapacitor with porous PANI electrodes. Due to the hierarchical porous structure, large surface area and the improved conductivity, the resulting devices show excellent volumetric capacitances, which are comparable to or much higher than those previously reported.