High power density supercapacitor devices based on nickel foam–coated rGO/MnCo2O4 nanocomposites

Abstract

New nanocomposite electrode material of rGO/MnCo 2 O 4 was freely loaded on flexible substrate on nickel foam and prepared by a simple, cost-effective, and eco-friendly pathway. The results show that the spinel manganese cobaltite (MnCo 2 O 4) with reduced graphene oxide (rGO) nanocomposite forms a uniform deposit and densely covers on the nickel foam (NF). The electrochemical measurements were investigated in three methods, such as cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS). The synergistic effects from rGO and MnCo 2 O 4 deliver outstanding an excellent electrochemical performance that was not realized by any of these components alone. The electroactive material exhibits a high specific capacitance of C sp = 808 F/g at 2 mV/s in 1 M KOH solution. Furthermore, this device delivers an excellent power density of P = 7658 W/kg and a high energy density of E = 15.2 Wh/kg. More importantly, cycling retention is 135% after 1000 charge/discharge cycles. This study proposes that the as-prepared (rGO/MnCo 2 O 4)/nickel foam has a potential application and a promising candidate for energy storage devices.

Effects of Heteroatom Doping and Physicochemical Character on the Electrochemical Properties of Graphene Sheets

“…Various hypotheses have been proposed to explain the origin of the capacitance increase of graphene electrodes while performing voltage and current scans. [6,7,47] Yadav et al [6] studied N-doped rGOs and suggested that the increase in specific capacitance may have resulted from the deposition of dissolved Pt content from the counter electrode or the electrochemical activation of the graphene's functional groups with the conducted scans. Another relevant study that focused on electrochemical functionalization showed that exceeding a certain anodic voltage limit of CV scans increases the graphene's specific capacitance and the reason was explained as additional defect formation based on variation of XPS measurements taken before and after the experiments.…”

“…[7] The increased wettability of the electrode surface also proposed as a possible explanation. [47] In this study, the electrodes were kept in DI water for a day before the measurement and the PBS electrolyte used on the measurements will not cause Pt dissolution. Therefore, the electrochemical functionalization of graphene and the separation of stacked graphene sheets by the applied voltage are the most likely explanations for the increase in specific capacitance.…”

“…To evaluate the cyclic stability of rGO and EEG samples, 300 successive CV scans were performed with HrGO and pristine EEG‐2 samples in the potential range of 0 V‐0.6 V. The EEG‐2 sample's specific capacitance has increased during performed scans (Figure 9a). Various hypotheses have been proposed to explain the origin of the capacitance increase of graphene electrodes while performing voltage and current scans [6,7, 47] . Yadav et al [6] .…”

“…Another relevant study that focused on electrochemical functionalization showed that exceeding a certain anodic voltage limit of CV scans increases the graphene's specific capacitance and the reason was explained as additional defect formation based on variation of XPS measurements taken before and after the experiments [7] . The increased wettability of the electrode surface also proposed as a possible explanation [47] …”