Facile and controllable in-situ nitridation of polyaniline electrode for high-performance flexible all-solid-state supercapacitors

Symmetrical supercapacitor is prepared with polyaniline (PANI) deposited on Au-coated porous nylon substrate as the electrodes and polyvinyl alcohol (PVA) /H2SO4 as the electrolyte. Successive abnormal phenomena occur that nylon becomes from opaque to transparent followed by PANI turning from green into black, also, the corresponding supercapacitor performance presents a significant improvement. The amide bond in the nylon is hydrolyzed by H2SO4 to form monomer, which is then esterified to produce aromatic ester by PVA combined with H2SO4 as the catalyst. The aromatic ester is transparent, thus leading to the nylon transparency. Moreover, the N-containing functional group in the nylon would be grafted to PANI by using the current collector Au as the catalyst, thus resulting in in-situ PANI nitridation with color turning from green into black. The in-situ PANI nitridation can be modulated (i) by controlling the nylon transparency, which can be modulated by the experimental temperature and humidity and (ii) by changing the current collector material, which serves as the catalyst to motivate the in-situ PANI nitridation. Due to high conductivity and high reversible redox reactivity of the nitrided PANI, the corresponding supercapacitor displays high specific capacitance (649.5 mF cm-2 at 0.5 mA cm-2), long cycling life (93.9% of the retained capacity after 6500 cycles), both high energy density and high power density (65.0 μW h cm-2 at 0.3 mW cm-2; 41.9 μW h cm-2 at 30.0 mW cm-2) and good flexibility.