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Supercapacitors (SCs) have proven remarkable interest in portable digital devices because of their long life span and high power densities. However, low energy densities of SCs hindered their applications due to the lack of high-performance negative electrode materials. In this work, we demonstrated the successful surface engineering of iron oxide nanoparticles (Fe 3 O 4 -NPs) by polyaniline (PANI) coating through a facile low-temperature hydrothermal method. The polyaniline coated iron oxide nanoparticles (Fe 3 O 4 /PANI-NPs) were characterized by a series of techniques including XRD, FT-IR, RAMAN, XPS, TGA, BET, SEM, and TEM. Fe 3 O 4 -NPs and Fe 3 O 4 /PANI-NPs are investigated as negative electrode materials for SCs in basic potassium hydroxide (KOH) electrolyte. The Fe 3 O 4 /PANI-NPs sample possesses specific capacitance of 1669.18 F g−1 while Fe 3 O 4 -NPs exhibits 1351.13 F g−1 at 1 A g−1 at identical conditions. The Fe 3 O 4 /PANI-NPs sample exhibits remarkable electrochemical cycling performance (96.5%) over pristine Fe 3 O 4 -NPs (92%) at high current density of 15 A g−1 by exceeding the 25,000 times charge/discharge cycles. The PANI coating not only offers a strong shell to avoid degradation of the material but also contributes to enhancing the capacitance with outstanding stability. Furthermore, we analyzed the charge storage contributions by implementing the power's law and interestingly Fe 3 O 4 /PANI-NPs sample exhibits high capacitive type storage (85% capacitive at 10 mVs−1). Based on our experiments, Fe 3 O 4 /PANI-NPs shows exceptional high electrochemical results in basic electrolyte with excellent stability and surpass most of recently reported work based on the iron oxides and their composites. Therefore, the proposed strategy can be applied to fabricate the high-performance negative electrode materials for supercapacitors. The Fe 3 O 4 /PANI-NPs electrode showed excellent electrochemical performance with outstanding cycling stability. Image 1 • Engineering the surface of Fe 3 O 4 -NPs by polyaniline coating. • Fe 3 O 4 /PANI-NPs supported on carbon cloth exhibit exceptional high charge storage. • Fe 3 O 4 /PANI-NPs displayed high capacitance of 1669.18 F g-1 at 1 A g-1. • Fe 3 O 4 /PANI-NPs electrode shows excellent cycling stability >95% over 25,000 cycles. [ABSTRACT FROM AUTHOR]

In this work, iron oxide (Fe 3 O 4) nanodiscs and anchored on reduced graphene oxide (rGO) as a nanocomposite (Fe 3 O 4 /rGO) have been fabricated through a surface, scalable hydrothermal process. The morphological and structural studies of Fe 3 O 4 /rGO nanodiscs are analyzed by various techniques such as XRD, XPS, SEM, TEM, and TGA, etc. The Fe 3 O 4 /rGO electrode is tested as a negative electrode in a basic potassium hydroxide (KOH) electrolyte using a three-electrode system for supercapacitor applications. The optimized electrochemical properties of Fe 3 O 4 /rGO are systematically compared with bare Fe 3 O 4 and it is found that the rGO greatly enhanced its performance as a negative electrode. The Fe 3 O 4 /rGO nanodiscs demonstrated a notably high-specific capacitance of 1149 F/g at 1.5 A/g better than that of Fe 3 O 4 nanodiscs (920 F/g at 1.5 A/g). Furthermore, the Fe 3 O 4 /rGO displays the superior cyclic stability of 97.53% after running continuous 10000 GCD cycles at a high current density of 10 A/g, while bare Fe 3 O 4 attained 87.82% at identical conditions. The fascinating electrochemical performance can be benefited for future fabrications of iron graphene-based negative electrode material for SCs. Image 1 • Fe 3 O 4 /rGO nanodiscs composite was prepared through the superficial hydrothermal method. • The use of rGO significantly enhances the properties of Fe 3 O 4 nanodiscs. • Fe 3 O 4 /rGO nanodiscs composite as a negative electrode is promising for electrochemical energy storage. • The Fe 3 O 4 /rGO composite exhibit a specific capacitance of 1149 F/g at 1.5 A/g. [ABSTRACT FROM AUTHOR]

[Display omitted] Supercapacitors (SCs) are receiving increasing attention owing to their unique characteristics, including moderate energy density, long service life, rapid discharge–charge rates, and exceptional safety. In this study, a ZnO-CeO 2 nanocomposite was synthesized via a facile hydrothermal method. The hexagonal nanorods of ZnO and the particle morphology of CeO 2 with high purity and crystallinity were confirmed using morphological and phase analyses. The cyclic voltammetry (CV) voltammogram from prolonged scan rates and the maximum response current in the three-electrode cell demonstrates the ZnO-CeO 2 nanocomposite ideal capacitive behavior. The ZnO-CeO 2 nanocomposite exhibited excellent electrochemical properties owing to the typical pseudocapacitive nature of fast redox reactions from Ce3+/Ce4+ and Zn2+ ions, with an initial capacitive contribution of 80 % at 10 mV s−1, calculated using the Dunn's method. It exhibited a high capacitance of 1040.9 F/g at a current density of 1 A/g and excellent long-term cycling stability (97.0 %) and rate capability (68.1 %) over 8000 charge–discharge cycles. Density functional theory (DFT) calculations indicated that the ZnO-CeO 2 composites show superior transport properties owing to the heterointerfaces of the formed heterostructure. The promising results of this study indicate that the ZnO-CeO 2 nanocomposite could be used as an electrode material for supercapacitors. [ABSTRACT FROM AUTHOR]