Facile synthesis of perovskite lanthanum aluminate and its green reduced graphene oxide composite for high performance supercapacitors

Abstract

A facile simple hydrothermal synthetic route has been developed for the synthesis of perovskite lanthanum aluminate (LaAlO3) and reduced graphene oxide composite (RGO). Green tea extract here is used as reducing agent for conversion of graphene oxide to reduced graphene oxide. The synthesized materials have been characterized for its morphology using, XRD, SEM, EDAX, FTIR and BET techniques. The materials are used as electrode materials for supercapacitor applications. Electron microscopic images indicate RGO sheets are densely attached to surface of LaAlO3 with perforated cage like morphology. A high specific capacitance of 721 F g−1 at a scan rate of 2 mV s−1 was exhibited by RGO/LaAlO3 hybrid structure electrode when compared to pure RGO (531 F g−1) and pure LaAlO3 (105 F g−1) electrodes at the same scan rate using cyclic voltammetry (CV). By using chronopotentiometry (CP), the RGO/LaAlO3 hybrid structure electrode out stretched specific capacitance of 283 F g−1 at a current density of 0.5 A g−1 and able to retain specific capacitance (Csp) of about 157 F g−1 even at very high current density of 20 A g−1. RGO/LaAlO3 composite also possesses an energy density of 57 Wh kg−1 with a maximum power density of 569 W kg−1. RGO/LaAlO3 nanocomposite has also been fabricated for asymmetric supercapacitor device (ASD) system. From the Electrochemical Impedance Spectroscopy (EIS), the RGO/LaAlO3 hybrid structure electrode has shown phase angle close to −90° for frequency up to 0.01 Hz, suggesting that the nanocomposite electrode material approached ideal capacitor behaviour.