Electrochemical Performance of Carbon Fiber / PANI / GO Electrodes for Energy Storage Devices: Supercapacitors

Abstract

Electro-electronic systems demand advances in energy storage by new technologies. Supercapacitor devices are required due to their electrochemical performance and need electrodes of materials capable of storing and conducting energy in a short time. The strong electroactivity of structures such as graphene oxide (GO) in combination with polyaniline (PANI) is given by π-π interactions and chemical bonds, favoring the movement of electrons [1,2]. The objective was to develop carbon fiber, PANI and GO electrodes with storage and dissipation of electrochemical energy applicable to supercapacitors. Electrosynthesis of aniline 0.5 mol L-1 and sulfuric acid 1.0 mol L-1 was performed by square wave voltammetry (potentials of 0.5 V and 1.05 V during 25 s in 15 repetitions, vs Ag/AgCl), on 4 cm of carbon fiber surface, containing 3000 cables. After it, the electrode was dried at room temperature for 24 hours, and a suspension of GO at 1.0 mol L-1 was dripped. Characterization was performed by SEM, EIS, GCD and cyclic voltammetry in H2SO4 1.0 mol L-1. PANI (PANI CR) grew uniformly, forming plaques, covering the entire length of the carbon fiber (Figure 1-A). When adding GO (PGO CR), it is possible to evidence a more elongated, pointed morphology, associated with the interaction of GO with PANI (Figure 1-B). The values of R1 (double layer) and R2 (active material) referring to electrical circuits (Figure 3, Table 1), by EIS (Figure 2), are lower for PGO CR, showing greater transfer of charges (conductivity). The capacitance, power density (501.64 W kg-1) and energy (27.17 Wh kg-1) values (Table 2) for PGO CR are higher in relation to PANI CR in 500 cycles (Figure 4). The values of power 1.9 kW kg-1 and energy of 33.33 Wh kg-1 (Figure 5, Table 3) of PGO CR, by cyclic voltammetry, are high, exceeding the threshold that is estimated for supercapacitors in terms of stored energy: high electroactivity and performance for more than 500 cycles, which can be applied to energy storage devices.