Operando Raman spectroelectrochemical study of polyaniline degradation: A joint experimental and theoretical analysis

Operando Raman spectroscopy of an electrode composed of the polyaniline is performed to elucidate the fundamental polarization mechanism occurring in an electrochemical supercapacitor during a large electroactive voltage window. The polyaniline presented two distinct redox processes; the first is associated with converting the leucoemeraldine base to the emeraldine and then with the conversion of emeraldine to the pernigraniline. By operando Raman spectroscopy, the exchange of the head-to-tail polarization mechanism by forming head-to-head coupling during voltammetric was verified. In the charging process, oxidized polyaniline forms polaron and bipolaron structures, causing deprotonation, while sulfate from the electrolyte inserting in the polyaniline chain causing a balance of the electronic charge. The materials modeling was shown to analyze the effects of the applied high potential and its correlation with the p-doping/dedoping sulfate anion and water molecules in the polyaniline chain. The density functional theory using van der Wall correction (DFT + vdW) simulation eluci-dated tensile stress with the insertion of sulfate anion and water molecules. It was not observed any hydrogen bond between polyaniline chain and sulfate anion, which facilitate and contribute to the conductivity of poly -aniline emeraldine-like structure.