Mo-doped ZnO nanoflakes on Ni-foam for asymmetric supercapacitor applications

Construction of a uniform zeolitic imidazole framework (ZIF-8) nanocrystal through a wet chemical route towards supercapacitor application

Exploring larger surface area electrode materials is crucial for the development of an efficient supercapacitors (SCs) with superior electrochemical performance. Herein, a cost-effective strategy was adopted to synthesize a series of ZIF8 nanocrystals, and their size effect as a function of surface area was also examined. The resultant ZIF8-4 nanocrystal exhibits a uniform hexagonal structure with a large surface area (2800 m2 g-1) and nanometre size while maintaining a yield as high as 78%. The SCs performance was explored by employing different aqueous electrolytes (0.5 M H2SO4 and 1 M KOH) in a three-electrode set-up. The SC performance using a basic electrolyte (1 M KOH) was superior owing to the high ionic mobility of K+. The optimized ZIF8-4 nanocrystal electrode showed a faradaic reaction with a highest capacitance of 1420 F g-1 at 1 A g-1 of current density compared to other as-prepared electrodes in the three-electrode assembly. In addition, the resultant ZIF8-4 was embedded into a symmetric supercapacitor (SSC), and the device offered 350 F g-1 of capacitance with a maximum energy and power density of 43.7 W h kg-1 and 900 W kg-1 at 1 A g-1 of current density, respectively. To determine the practical viewpoint and real-world applications of the ZIF8-4 SSC device, 7000 GCD cycles were performed at 10 A g-1 of current density. Significantly, the device exhibited a cycling stability around 90% compared to the initial capacitance. Therefore, these findings provide a pathway for constructing large surface area ZIF8-based electrodes for high-value-added energy storage applications, particularly supercapacitors.

Phyto-synthesized facile Pd/NiOPdO ternary nanocomposite for electrochemical supercapacitor applications

The natural phyto bio-factories were successfully utilized for the cost-effective synthesis of facile Pd/NiOPdO ternary nanocomposite for energy storage application with enhanced electro-active site.

Fabrication of Fe3O4-incorporated MnO2 nanoflowers as electrodes for enhanced asymmetric supercapacitor performance

Manganese dioxide (MnO2) is considered a promising aspirant for energy storage materials on account of its higher theoretical capacitance along with low capital cost.

Facile ZnO-based nanomaterial and its fabrication as a supercapacitor electrode: synthesis, characterization and electrochemical studies

In recent times, tremendous efforts have been devoted to the efficient and cost-effective advancements of electrochemically active metal oxide nanomaterials. Here, we have synthesized a facile nanomaterial of ZnO@PdO/Pd by employing extracted fuel from E. cognata leaves following a hydrothermal route. The phyto-fueled ZnO@PdO/Pd nanomaterial was fabricated into a supercapacitor electrode and was scrutinized by galvanostatic charge–discharge, electrochemical impedance spectroscopy and cyclic voltammetry to evaluate its energy storage potential, and transport of electrons and conductivity. Substantial specific capacitance i.e., 178 F g⁻¹ was obtained in the current study in aKOH electrolyte solution. A specific energy density of 3.7 W h Kg⁻¹ was measured using the charge–discharge data. A high power density of 3718 W Kg⁻¹ was observed for the ZnO@PdO/Pd electrode. Furthermore, the observed low internal resistance of 0.4 Ω suggested effective electron- and ion diffusion. Thus, the superb electrochemical behavior of the ZnO@PdO/Pd nanocomposite was exposed, as verified by the significant redox behavior shown by cyclic voltammetry and galvanostatic charge–discharge.

In recent times, tremendous efforts have been devoted to the efficient and cost-effective advancements of electrochemically active metal oxide nanomaterials.

Electrospun carbon nanofibers embedded with MOF-derived N-doped porous carbon and ZnO quantum dots for asymmetric flexible supercapacitors

Hierarchical carbon nanofibers are embedded with MOF-derived N-doped porous carbon nanoparticles and decorated with ZnO quantum dots via a co-spinning method.

Biomimetic Catalysts Based on Au@ZnO-Graphene Composites for the Generation of Hydrogen by Water Splitting

For some decades, the scientific community has been looking for alternatives to the use of fossil fuels that allow for the planet's sustainable and environmentally-friendly development. To do this, attempts have been made to mimic some processes that occur in nature, among which the photosystem-II stands out, which allows water splitting operating with different steps to generate oxygen and hydrogen. This research presents promising results using synthetic catalysts, which try to simulate some natural processes, and which are based on Au@ZnO-graphene compounds. These catalysts were prepared by incorporating different amounts of gold nanoparticles (1 wt.%, 3 wt.%, 5 wt.%, 10 wt.%) and graphene (1 wt.%) on the surface of synthesized zinc oxide nanowires (ZnO NWs), and zinc oxide nanoparticles (ZnO NPs), along with a commercial form (commercial ZnO) for comparison purposes. The highest amount of hydrogen (1127 μmol/hg) was reported by ZnO NWs with a gold and graphene loadings of 10 wt.% and 1 wt.%, respectively, under irradiation at 400 nm. Quantities of 759 μmol/hg and 709 μmol/hg were obtained with catalysts based on ZnO NPs and commercial ZnO, respectively. The photocatalytic activity of all composites increased with respect to the bare semiconductors, being 2.5 times higher in ZnO NWs, 8.8 times higher for ZnO NPs, and 7.5 times higher for commercial ZnO. The high photocatalytic activity of the catalysts is attributed, mainly, to the synergism between the different amount of gold and graphene incorporated, and the surface area of the composites.

Organic template-assisted green synthesis of CoMoO4 nanomaterials for the investigation of energy storage properties

Transitional metal oxide nanomaterials are considered to be potential electrode materials for supercapacitors. Therefore, in the past few decades, huge efforts have been devoted towards the sustainable synthesis of metal oxide nanomaterials. Herein, we report a synergistic approach to synthesize spherical-shaped CoMoO₄ electrode materials using an inorganic-organic template via the hydrothermal route. As per the synthesis strategy, the precursor solution was reacted with the organic compounds of E. cognata to tailor the surface chemistry and morphology of CoMoO₄ by organic species. The modified CoMoO₄ nanomaterials revealed a particle size of 23 nm by X-ray diffraction. Furthermore, the synthesized material was scrutinized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, field emission scanning electron microscopy and energy dispersive spectroscopy. The optical band gap energy of 3.6 eV was calculated by a Tauc plot. Gas chromatography-mass spectrometry identified cyclobutanol (C₄H₈O) and octodrine (C₈H₁₉N) as the major stabilizing agents of the CoMoO₄ nanomaterial. Finally, it was revealed that the bioorganic framework-derived CoMoO₄ electrode exhibited a capacitance of 294 F g^-1 by cyclic voltammetry with a maximum energy density of 7.3 W h kg^-1 and power density of 7227.525 W kg^-1. Consequently, the nanofeatures and organic compounds of E. cognata were found to enhance the electrochemical behaviour of the CoMoO₄-fabricated electrode towards supercapacitor applications.

CuCo2O4 nanoneedle array with high stability for high performance asymmetric supercapacitors

Cycling performance is very important to device application. Herein, a facile and controllable approach is proposed to synthesize high stability CuCo₂O₄ nanoneedle array on a conductive substrate. The electrode presents excellent performances in a large specific capacitance up to 2.62 F cm⁻² (1747 F g⁻¹) at 1 mV s⁻¹ and remarkable electrochemical stability, retaining 164% even over 70 000 cycles. In addition, the asymmetric supercapacitor assembled with the optimized CuCo₂O₄ nanoneedle array (cathode) and active carbon (anode), which exhibits superior specific capacity (146 F g⁻¹), energy density (57 W h kg⁻¹), and cycling stability (retention of 83.9% after 10 000 cycles). These outstanding performances are mainly ascribed to the ordered binder-free nanoneedle array architecture and holds great potential for the new-generation energy storage devices.

The CuCo₂O₄ nanoneedle array with enhanced electrochemical performance especially high stability is due to the hierarchical porosity framework with the high mesoporous nanoneedle array.