The quick responsive and durable supercapacitive performance was achieved from reduced graphene oxide/ zinc hydroxide/polyaniline (rGO5.88%/Zn(OH)$_2$11.77%/PANI82.35%) (GZnP82) nanocomposite, synthesized by in-situ single step. The GZnP82 provided a specific capacitance ($C_s$) of 173.60 F g$^{–1}$, a specific capacity ($Q$) of 208.32 C g$^{–1}$, a specific energy of 34.7220 W h kg$^{–1}$ and a specific power of 1516.8 W kg$^{–1}$ at 0.25 A g$^{–1}$. The GZnP82 exhibits only 28% decay of its initial $C_s$ up to 12500 cycles at 2 A g$^{–1}$. The GZnP82 is fast in response with the relaxation time (${\tau}$) of 1.52 s. The capacitance of GZnP82 device obtained from impedance spectroscopy is 1.29 F. The comparison of electrochemical performance of GZnP82 measured from both chronopotentiometry and impedance spectroscopy, with similar reported energy storage materials, apprises that the achieved performances are of similar order; and better than, the reported materials. Most importantly, the addition of Zn(OH)$_2$ has rendered the negative contribution to the GZnP82, as the binary combination of it, the rGO/PANI furnished higher performances than the GZnP82.

The influences of base and salt forms, dopants used for protonation and different oxidation states of polyaniline (PANI) on its crystal structure, morphology, electrochemical stability, electrical conductivity and different potential-dependent energy storage by electrochemical processes were investigated by synthesizing PANI with two different acid dopants and in two different redox forms. The results reveal that, the methane sulphonic acid (MSA) causes more storage of energy in PANI. The reduced form of PANI furnishes high surface area and stores more energy than the respective oxidized form. The MSA-doped PANI exhibits an inimitable property of increase of specific capacitance ($C_s$) with increase in number of charge/discharge cycles in both oxidized and reduced forms. The structural changes of PANI after 25600 cycles were determined by IR spectroscopy, which confirmed that the irreversible formation of pernigraniline causes property degradation of PANI. The maximum energy storage parameters obtained from oxidized form of PANI doped with MSA (PANIMSA-Ox) are a $C_s$ of 458 F g$^{-1}$, a specific energy ($E_s$) of 91 W h kg$^{-1}$ and a specific power ($P_s$) of 2.0983 kW kg$^{-1}$ at 1 A g$^{-1}$. In addition, the PANIMSA-Ox exhibits an exceptional cyclic stability up to 25600 at 0.4 V s$^{-1}$. The theoretical capacitance of PANI (2000 F g$^{-1}$) is nearly reached with PANIMSA-Ox as it provided the $C_s$ of an electrode of 1834.84 F g$^{-1}$ at 1 A g$^{-1}$. Most significantly, the PANIMSA-Ox presents the maximum of four faradaic couples and exceptional energy storage without using any redox supporting electrolytes.