g-C3N4 nanosheet@CoAl-layered double hydroxide composites for electrochemical energy storage in supercapacitors

This study reports the high capacitance and cyclic stability of CoAl-layered double hydroxide (CoAl-LDH) nanoflowers decorated with graphitic C3N4 nanosheets (g-C3N4) as a new electrode material for supercapacitor applications. The proposed composite is fabricated through a convenient solvothermal method and its structural features are unraveled by XRD, FESEM and FT-IR spectroscopy. The electrochemical behavior of the composite is assessed using cyclic voltammetry, galvanostatic charge/discharge evaluations and impedance spectroscopy. It is demonstrated that adding various amounts of g-C3N4 nanosheets to the LDHs can promote its electrochemical properties by combining the redox reactivity of the LDH host with the considerable electronic conductivity of the g-C3N4 guest. According to the electrochemical measurements, in three electrode system, the introduced nanocomposite can present a high specific capacitance (343.3 F g−1) at 5 A g−1 current density. In addition, to investigate the performance of the composite material in storage of energy, an asymmetric supercapacitor is devised using the optimal nanocomposite and activated carbon, as the positive and negative electrode materials, respectively. It is declared out that the developed supercapacitor can produce a maximum energy density of 61.15 W h kg−1, and 13,994.66 W kg−1 power density, and exhibit outstanding high-current capacitive characteristics. So that, it can present 93% of the composite's initial capacitance after 6000 cycles. Furthermore, it is found out that the use of two series of the proposed asymmetric supercapacitor is sufficient for supplying energy for a red light emitting diode (LED) for 20 min, which indicates the high potential of the supercapacitor for practical applications. The study is a firm step towards developing alternative electrode materials with the purpose of acquiring a higher energy storage capacity from the available supercapacitors.