Hydrothermal Synthesis of Vanadium Pentoxides–Reduced Graphene Oxide Composite Electrodes for Enhanced Electrochemical Energy Storage

Abstract

Graphene-based nanomaterials (graphene nanosheets/graphene nanoribbons) decorated with vanadium pentoxide (V₂O₅) nanobelts (i.e. GVNBs) were synthesized via one-step low-temperature facile hydrothermal/solvothermal method as high-performance electrochemical composite electrodes. VNBs were formed in the presence of graphene oxide (GO), a mild oxidant, which transforms into reduced GO (rGO_HT) assisted in enhancing the electronic conductivity with mechanical strength for GVNBs. From surface sensitive electron microscopy and spectroscopy structural characterization techniques and analyses, rGO_HT nanosheets/ nanoribbons appear to be inserted into and coated with the layered crystal structure of VNBs, which further confirmed the enhanced electrical conductivity of VNBs. The electrochemical energy storage capacity of GVNBs is investigated using electrochemistry and the specific capacitance C_s are determined from both the cyclic voltammetry (CV) with scan rate and galvanostatic charge/discharge V-t profiles with varying current density. The GVNBs having rGO-rich composite V₁G₃ (V₂O₅/GO = 1:3) showed superior performance followed by V₂O₅-rich V₃G₁ (V₂O₅/GO = 3:1) as compared with V₁G₁ (V₂O₅/GO = 1:1) composites besides pure component (rGO_HT and V₂O₅) materials. Moreover, V₁G₃ and V₃G₁ composites showed excellent cyclic stability and the capacitance retention of > 80% after 200 cycles. Furthermore, by performing extensive simulations and modeling of electrochemical impedance spectroscopy data, we determined various circuit parameters (charge transfer and solution resistance, double layer and low frequency capacitance). These findings highlight the comparative performance of nanocomposite hybrid electrode materials.