Electrochemical Measurement and Simulation of Sulfuric Acid-Doping Polyaniline on Graphite Carbon Paper

The sulfuric acid-doping polyaniline (H-PANI-HSO 4 ) are applied to conduct the electrochemical measurement and simulation calculation to investigate the capacitance, electronic structure and energy band properties. The H-PANI-HSO 4 growing on graphite carbon paper (H-PANI-HSO 4 /GCP) is applied as an electroactive electrode to investigate electrochemical properties. The Faradaic capacitance of H-PANI-HSO 4 /GCP electrode is ascribed to the reversible redox reaction of bisulfate anion doping/dedoping protonated PANI (H-PANI). Cyclic voltammetry measurement at a scan rate of 5[Formula: see text]mV[Formula: see text]s[Formula: see text] determines an equivalent mean response current of 0.64[Formula: see text]A[Formula: see text]g[Formula: see text] and a capacitance of 128.35[Formula: see text]F[Formula: see text]g[Formula: see text]. Galvanostatic charge–discharge measurement determines specific capacitance from 129.06 to 116.88[Formula: see text]F[Formula: see text]g[Formula: see text] at current densities from 0.5 to 2.5[Formula: see text]A[Formula: see text]g[Formula: see text]. Cyclic voltammetry-based capacitance at equivalent current density of 0.64[Formula: see text]A[Formula: see text]g[Formula: see text] is in accordance with galvanostatic charge–discharge-based capacitance at the current density of 0.57[Formula: see text]A[Formula: see text]g[Formula: see text]. Electrochemical impedance spectrum measurements indicate that H-PANI-HSO 4 /GCP exhibits lower charge-transfer resistance, much lower Warburg resistance, higher quasicapacitance than H-PANI-HSO 4 to approaching ideal capacitor. Density functional theory calculations indicate that H-PANI-HSO 4 has a higher density of states (10.6 electron/eV) and lower bandgap energy (0.481[Formula: see text]eV) than H-PANI (5.24 electron/eV, 1.449[Formula: see text]eV), indicating its enhanced electronic conductivity. The electronic bandgap energy is accordingly decreased from 0.263[Formula: see text]eV for H-PANI-HSO 4 /GCP to 0 for H-PANI-HSO 4 /GCP. Electrochemical measurement and simulation calculation investigation proves that H-PANI-HSO 4 /GCP electrode with anion-doped and protonated state exhibits higher electronic conductivity and capacitance performance to act as superior electroactive material.