Comparison of the electrochemical performance of self-cross-linked and free-standing polyaniline electrodes

Cross-linked polyaniline (PANI) gel can provide rapid transfer channels for electrons and ions, and self-cross-linked PANI (SC-PANI) electrodes have been previously reported. However, there are few reports on the preparation of free-standing PANI (FS-PANI) electrodes. Hence, new preparation technologies are required for FS-PANI electrodes and their electrochemical performance must be estimated. Moreover, FS-PANI must be compared with SC-PANI to better estimate their performance. In this study, SC-PANI was prepared using p-phenylenediamine (PPD), phytic acid, aniline (An), and ammonium persulfate as the additive, doping acid, monomer, and oxidant, respectively. Then, it was hydrothermally transformed into FS-PANI. The microstructures of SC-PANI and FS-PANI were characterized using scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy, and their electrochemical performances were tested using cyclic voltammetry, galvanostatic charge–discharge (CD) measurement, and electrochemical impedance spectroscopy. When the molar ratio of PPD to An was 0.10, the electrochemical performance of SC-PANI was the best as it achieved the largest specific capacitance (Cs) (403 F/g) and lowest internal resistance. After 2000 CD cycles, Cs remained at 73%. However, the Cs of FS-APNI was 511 F/g and 97% of the initial Cs value was maintained after 2000 CD cycles. This study is expected to provide an effective basis for the future research on free-standing electrode materials for supercapacitors.