Experimental and computational investigation on the charge storage performance of a novel Al2O3-reduced graphene oxide hybrid electrode

Abstract

The advancements in electrochemical capacitors have noticed a remarkable enhancement in the performance for smart electronic device applications, which has led to the invention of novel and low-cost electroactive materials. Herein, we synthesized nanostructured Al₂O₃ and Al₂O₃-reduced graphene oxide (Al₂O₃-rGO) hybrid through hydrothermal and post-hydrothermal calcination processes. The synthesized materials were subject to standard characterisation processes to verify their morphological and structural details. The electrochemical performances of nanostructured Al₂O₃ and Al₂O₃- rGO hybrid were evaluated through computational and experimental analyses. Due to the superior electrical conductivity of reduced graphene oxide and the synergistic effect of both EDLC and pseudocapacitive behaviour, the Al₂O₃- rGO hybrid shows much improved electrochemical performance (~ 15-fold) as compared to bare Al₂O₃. Further, a symmetric supercapacitor device (SSD) was designed using the Al₂O₃- rGO hybrid electrodes, and detailed electrochemical performance was evaluated. The fabricated Al₂O₃- rGO hybrid-based SSD showed 98.56% capacity retention when subjected to ~ 10,000 charge-discharge cycles. Both the systems (Al₂O₃ and its rGO hybrid) have been analysed extensively with the help of Density Functional Theory simulation technique to provide detailed structural and electronic properties. With the introduction of reduced graphene oxide, the available electronic states near the Fermi level are greatly enhanced, imparting a significant increment in the conductivity of the hybrid system. The lower diffusion energy barrier for electrolyte ions and higher quantum capacitance for the hybrid structure compared to pristine Al₂O₃ justify improvement in charge storage performance for the hybrid structure, supporting our experimental findings.