Experimental and computational investigation on the charge storage performance of a novel Al ₂O ₃-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 Al ₂O ₃ and Al ₂O ₃-reduced graphene oxide (Al ₂O ₃-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 Al ₂O ₃ and Al ₂O ₃- 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 Al ₂O ₃- rGO hybrid shows much improved electrochemical performance (~ 15-fold) as compared to bare Al ₂O ₃. Further, a symmetric supercapacitor device (SSD) was designed using the Al ₂O ₃- rGO hybrid electrodes, and detailed electrochemical performance was evaluated. The fabricated Al ₂O ₃- rGO hybrid-based SSD showed 98.56% capacity retention when subjected to ~ 10,000 charge–discharge cycles. Both the systems (Al ₂O ₃ 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 Al ₂O ₃ justify improvement in charge storage performance for the hybrid structure, supporting our experimental findings.