We report fabrication of flexible all-solid-state transparent electrochromic patterned microsupercapacitors based on twodimensional layered nanostructured molybdenum oxide (MoO 3−x )/ poly(3,4-ethylenedioxythiophene)−polystyrenesulfonate (PE-DOT:PSS) nanocomposite electrodes. Exceptional electrochemical performance of the transparent microsupercapacitors includes fast kinetics and response times, high specific capacitances (up to 79.2 C/ g, 99 F/g, and 2.99 mF/cm 2 ), and Coulombic efficiencies of 99.7% over 2500 cycles. Such exceptional performance is attributed to the synergistic effects of PEDOT:PSS providing high electrical conductivity and high charge storage capacity along with its segregated interfacial nanostructure facilitating the intercalation of the ionic species, H + (Na + , K + ) and SO 4 2− , into the high surface area tunnel structure of the 2D MoO 3−x nanosheets. Supercapacitors using MoO 3−x PEDOT:PSS electrodes exhibit optical transmittance above 70% (λ = 380−730 nm). The electrochromic performance of the transparent microsupercapacitor is due to both PEDOT:PSS and cation (H + ) intercalation in the tunnel structure of MoO 3−x .
By combining electrochemical experiments with mass spectrometric analysis, it is found that using short chain oligomers to improve the cycling stability of conducting polymers in supercapacitors is still problematic. Cycling tests via cyclic voltammetry over a potential window of 0 to 1.0 V or 0 to 1.2 V in a two-electrode device configuration resulted in solid-state electropolymerization and chain scission. Electropolymerization of the aniline tetramer to generate long chain oligomers is shown to be possible despite the suggested decrease in reactivity and increase in intermediate stability with longer oligomers. Because aniline oligomers are more stable towards reductive cycling when compared to oxidative cycling, future conducting polymer/oligomer-based pseudocapacitors should consider using an asymmetric electrode configuration.
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